Make Driving Fun! Inside the Ups & Downs of Dampers

Topic #10 from our series.

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Read on for more expert advice on transforming your Mustang into a high-performance handling machine. This week's topic is all about dampers, one of the key elements to creating a good-handling Mustang. (If you missed the previous episodes, they're posted on our website in the FAQs & Tech Tips section.)

Please note that what we're talking about here are dampers&#;not dampeners. Often misspelled and mispronounced as "dampener," "damper" is the correct term for today's subject, high performance struts and shocks for your Mustang. For the record, a dampener is something that makes something else damp, i.e., moist. If your dampers turn into dampeners you need new dampers.

OK, it's a damper. Why is it called that?
"Damper" comes from the primary function of a shock or strut, which is to control spring oscillation by damping, i.e., calming it down or reducing it. After an initial compression or extension, a spring will vibrate for quite some time unless something damps the oscillation. A damped oscillation is one that fades away to zero over time. A damper, in the case of a late model Mustang in the form of a strut or shock, damps the spring's natural tendency to oscillate. When the strut or shock is well matched to the spring it controls, the spring oscillation will damp to zero very quickly, usually in only one complete oscillation cycle. If your Mustang had no dampers it would bounce uncontrollably while driving down the road, as hitting a succession of bumps would add new spring oscillations on top of the slowly fading oscillations of previous bumps. Not a sexy look, in our opinion, and downright dangerous.

What's the difference between a shock and a strut?
While a shock is primarily a damper, it may also have secondary functions. For example, a shock may also be used to limit suspension droop travel, to limit suspension jounce (bump) travel, or to mount a spring (commonly called a coil-over design).

On the other hand, a strut has an additional function over that of a shock; it's an integral structural link that helps define the suspension geometry. If you remove a strut from the car's suspension, the wheel will flop about as the geometry of the suspension is no longer completely defined. This cannot happen when you remove a shock from the suspension. Struts are made quite robustly because they are structural links and must withstand high bending loads from cornering and braking.

All to present Mustangs left Ford's assembly line with a strut front suspension and shocks in the rear suspension.

How a damper damps
The suspension springs and the car's mass form a resonant system; think of a guitar. Once activated by a bump, like plucking a string, the spring (string) and mass (car or guitar body) will continue to vibrate for a long time unless the energy is more quickly absorbed by a damper. On a guitar, you can stop the vibration by putting a finger on the string you plucked. In a Mustang, the damper works something like that finger to stop the spring from oscillating.

Give me some details on this spring oscillation thing.
Here's the big picture of how a damper does its work: it converts kinetic energy (motion) into heat. In the case of a Mustang, the hydraulic dampers have a piston inside an oil-filled tube. The piston moves up and down as the suspension moves. The piston motion forces hydraulic oil through a number of small holes. As the oil moves it heats up from friction, which dissipates the kinetic energy.

There are many different damper designs. Some of the differences are large, such as monotube vs. twin-tube, gas charged or not, high-pressure gas vs. lower pressure, adjustable damping or fixed. Other differences are small, and include a myriad of little design differences affecting a damper's performance and effectiveness.

What else does a damper do?
Dampers help keep the tires' tread in contact with the pavement. As every Mustang (and driving) enthusiast knows, that's pretty much the most important thing! They control how quickly weight transfers when braking, turning into a corner, and while accelerating (whether out of a fun curve on your commute or during a drag strip launch).

Dampers produce a force based on how fast the shaft moves, so the amount of damping produced is somewhat proportional to the shaft velocity. The damper only produces a force when it's moving. Good dampers will alter the amount of force according to the shaft velocity. The specifics of the valving design and resulting damping at different velocities affect ride quality as well as performance.

How much damping do you need?
The exact amount can be difficult to quantify&#;and more difficult to achieve&#;especially over a range of shaft velocities. Too much damping reduces tire grip and makes ride quality worse. Too little damping leads to vehicle instability because the spring oscillations are uncontrolled. Since both overdamping and underdamping reduce tire grip, getting it right is quite a trick!

If you're up for some technical stuff, in general, the suspension needs more damping forces at low shaft velocities. More damping is required during turning, braking and accelerating, when the velocity of the shafts in the dampers is low (1"-3"/sec). When the car goes over sharp bumps, the shaft velocities are going to be much higher (10"-20"/sec). To maintain decent ride quality, higher velocities require lower damping forces.

Different Damper Designs
Monotube dampers
This design has a single tube mostly filled with oil. A piston rides inside the tube, with the oil on each side. At one end of the tube, separated from the oil by a second piston, is a section containing a high-pressure gas.

The damping is accomplished by the piston moving up and down in the oil, driven by a rod extending outside of the exterior tube. Oil moves through the piston, allowing the piston and shaft to move inside the tube. The oil's movement is carefully controlled by various holes and valves. The piston design and its valves and orifices are what determine the damping characteristics of the strut or shock. Kind of an amazing engineering feat!

The high-pressure gas keeps the oil from cavitating (creating gas bubbles in the oil) in a not-wanted process called foaming. Foamed oil has a much lower viscosity than bubble-less oil and significantly reduces the damping action.

Twin tube dampers
This design has two tubes, one inside the other. The piston rides inside the inner tube. The space between the inner and outer tubes serves as a reservoir for the oil displaced when the shock shaft moves in and out of the damper body. This reservoir can also contain a separate low-pressure gas reservoir. A valve connects the inner cylinder to the outer (reservoir) cylinder.

Just as with a monotube damper, the piston has valves and holes to control oil flow. That determines the damper's characteristics, or how much it damps.

Click on the image for a larger version.

Which is more effective?
Ah, good question. Monotube dampers have better heat dissipation than twin tube dampers because the oil doesn't have to go through as much material and distance to radiate heat into the outside environment. As the damper does more work, the temperature of the oil increases, which lowers its viscosity, which reduces its damping ability. This gives monotube dampers an advantage in high-performance applications, where the damper is worked harder.

Monotube dampers also have larger pistons that allow more fluid to flow through the valve for a given amount of suspension travel. This allows the piston valves to create a damping curve with a better tradeoff between ride quality and handling.

Pro Tip: Dampers have a very large effect on transient handling and ride quality. In fact&#;and most people don't know this&#;they have far more effect on ride quality than springs do!

Two other factors to consider: rebound and compression
Compression
This is when the spring and damper compress, when your Mustang hits a bump, or on the outside of the car when the body rolls during cornering. The spring and corresponding damper compress, allowing the suspension to absorb the bump. As the unsprung mass (tire, wheel, and suspension) moves upward toward the chassis, the damper turns this kinetic energy into heat so the chassis doesn't oscillate in an uncontrolled way in response to the bump. Picture the old beaters you've seen in grocery store parking lots heaving and bouncing up and down as they hit speed bumps. Good dampers prevent that. The compression valving in the damper is designed to keep this oscillation under control.

Rebound
This is when the spring and damper extend in situations such as after compressing to absorb a bump, or when the tire drops into a depression, or on the side of the car toward the inside of the turn when the body rolls during cornering. The unsprung mass (suspension, tires, and wheels) is moving away from the chassis of the car. When the suspension is moving in this direction, the damper is damping the kinetic energy stored in the sprung mass, turning it into heat.

Either way, during compression and rebound, good dampers damp vertical chassis movement to keep spring oscillation to a minimum, keeping the tires on the road and you in control.

Adjustable Dampers
Adjustable dampers have a provision to allow adjusting their damping force level. A damper labeled "SA" has one adjustment (single adjustable). A damper labeled "DA" has two adjustments (double adjustable).

There are two types of SA adjustment. With some dampers the adjustment changes only the amount of rebound force (typical of Koni). With other SA dampers, the adjustment changes both rebound and compression forces at the same time (typical of Tokico). Note: these settings are paired, not independent. With DA dampers, one adjustment is typically for rebound forces and the second is for compression forces. With DA dampers the adjustments are independent of each other.

Adjustable dampers can offer an advantage by letting you tune the transient handling behavior of the car, like if you have a weekend autocross that you're driving to and from. If you know what you're doing, you'll want softer settings on your way to the event to avoid spilling your morning coffee, and more performance-oriented settings while on the course.

However, this type of tuning requires knowledge and time to learn when and how to adjust the dampers. You need to determine what handling behavior you want to change, and then know what you should adjust, at which end of the car, and in which direction. That requires a skill set that many enthusiasts don't need for how they enjoy their Mustangs. Often, fixed dampers are a better solution because they can't be misadjusted, and they just need to damp the springs you're using with them.

Why MM carries only certain dampers
There are many dampers available for late model Mustangs in a wide range of prices, quality, and features. Here at MM we're interested in improved performance, so we ignore the stock-replacement dampers, like those you'll find at your local auto parts store. Among performance-oriented dampers the old saying "you get what you pay for" holds true, but with some surprising exceptions: some manufacturers offer "high-performance" dampers that don't provide anywhere near the performance level advertised. Have no fear: you won't find those on the MM website.

That leads us to why we carry the dampers we do. Our primary requirement is excellent quality, of course, but we also look for whether there are versions suitable for street use and versions for track performance aimed at the amateur racing-on-a-budget enthusiast.

Two favorites, Koni and Bilstein, are excellent for street-driven Mustangs and those taken to open-track events. But many years ago we discovered their limitations for top-level amateur road racing. That moved us to develop our own line of MM Dampers based on Bilstein internal components. With our own dampers, we can offer several versions, each tailored to different uses and their own appropriate spring rates, plus additional features the big manufacturers don't offer.

Note: We also like Tokico. Their D-spec and Illumina series are excellent for street & strip Mustangs. However, they left the U.S. market and the remaining selection of new Tokico dampers is sadly scanty.

And now, back to why MM Dampers are awesome. Seriously.
Damper design isn't easy; if it was, then all manufacturers would be making great products. In reality, there are more sub-par dampers on the market than good ones.

We put a lot of development time into our dampers. Designing and building a good damper requires a ton of work, and they're by far the most difficult part of the suspension system to get right. If your dampers are bad, they can make an otherwise great suspension design handle and ride like an ox cart.

For a damper intended for street use, there's always a tradeoff between good ride quality and good handling. Small differences in the damper design can skew the results too far in one direction, or even ruin both ride quality and handling.

When developing damper valving, the MM engineering team tests prototypes on a damper dynamometer, commonly called a "shock dyno." This machine extends and compresses the damper at varying velocities, while measuring and recording the forces created by the damper. Once we're happy with the dyno behavior, the damper goes onto a Mustang for real-world ride and handling testing.

Here's a generalized example of how the results of a shock dyno test look:

Click on the image for a larger version.

For on-car testing, we use a sophisticated Motec data logging system. This system has suspension travel sensors on all four corners, accelerometers for all three axes', a yaw sensor, and sensors for all the other basics such as throttle position, wheel speed, etc. We analyze the logged data to help design the next iteration of damper valving. Then it's back to the shock dyno. We repeat this process until the results meet our design goals for the ride and handling characteristics we're looking for.

Most MM dampers have fixed valving (check out the dampers listed for your Mustang to see our current offerings). This best suits the needs of most of our customers. Even for many in competitive road racing, the fixed valving provides the best results. Other than matching the MM series to your chosen spring rates, there's no need for any fiddling with damper tuning at the track (or on the street). That lets you concentrate on driving and improving your skills, rather than being a test driver.

You need a unique skill set to be a good test driver, including being able to evaluate the car's handling behavior to decide what changes to make to the dampers, if any. With adjustable dampers, decisions need to be made:

• Can better handling be achieved by adjusting the dampers?
• Should compression be increased or decreased?
• Should rebound be increased or decreased?
• Should those changes be made at the front, or the rear, or both?

You need a unique skill set to be a good test driver, including being able to evaluate the car's handling behavior to decide what changes to make to the dampers, if any.

That's a lot of decisions for an amateur racer. If you're up for it, MM does have very sophisticated high-end DA dampers for some applications, with more to come. At a more modest price level, we recommend Koni SA or DA dampers.

Matching dampers to springs
We've only been talking about dampers, but they're really just half of the important "springs and dampers" component of making a Mustang handle really well. Back in Episode 5 of this series we talked about springs in depth. We always recommend you choose the springs for your Mustang first&#;then get dampers to match. To help you make decisions we have a popular and handy Guide to Choosing Spring Rates and Dampers. The next step is contacting our Tech Associates for advice. For more advanced help, we have a Technical Services option to evaluate your situation and recommend springs and dampers just for your Mustang; choose the "Spring Rate" option.

Thanks for reading! Over the last 10 weeks we've presented the essentials of setting up a Mustang suspension that works really, really well. We hope you know now that elevating your Mustang's handling to being tremendous fun to drive in the twisties is a goal you can achieve.

If you've missed any of our popular Make Driving Fun! articles or want to forward them to a friend, you can read them all on our FAQs & Tech Tips page. Meanwhile, MM Tech Associates are standing by to help you get going on your project list to achieve maximum fun in your Mustang! More to come soon from your favorite car nerds at MM.

00:00

- In this module, we're talking all about the practicalities of damper tuning.

00:03

So before we get started, I just want to recap a couple of the basics of how we're using, or what we're using our dampers for in the first place.

00:10

So in the course, we broke things roughly down into the low speed and high speed regions, low speed being roughly anything less than 25 mm a second of shaft speed and high speed being roughly anything above that.

00:23

It's worth noting as well that there are plenty of people that have their own definitions for the boundary of low speed and high speed.

00:28

Some people use everything up to 50 mm per second or even 75 mm per second.

00:32

It really depends a lot on your application and maybe what type of racing you're doing depending on where you put that boundary, it doesn't really matter as long as you are clear about where you're putting that boundary.

00:41

In the low speed regime, this is really where the dampers are controlling things more like how much the car pitches or how fast the car pitches under braking.

00:50

The speed it rolls at when it rolls into the corner and how fast the rear of the car, if it's rear wheel drive, squats at the exit of a corner.

01:00

The important thing to remember about everything about the low speed section is that in low speed we're not controlling how much the car moves with the dampers, we're just controlling how fast it gets there.

01:10

So if we're talking about turning into a corner and we're using low speed damping to control that, the dampers, no matter what we set them to, as long as it's something reasonable, they won't control how far the car rolls at the mid corner, they'll only control how fast it gets there or how long it takes for the car to roll into that state and it's really that balance between the front and the rear dampers that's going to control a lot of our transient corner entry balance that we'll discuss a lot more as we move throughout this section.

01:36

As far as the high speed part of the damping curve, this is all about dealing with bumps and irregularities, curbs, pot holes, dips in the road where you've got section changes, ripples in the road where maybe the track has started to bundle up like it does sometimes in the braking zones where it gets compressed over time.

01:56

This is really where we're talking about the high speed regime of our damping.

02:01

Another thing we mentioned previously in the course is the type of damping philosophy that you take depending on both the type of racing that you're doing but also the type of car that you're working with.

02:11

So broadly I've put those into two categories of a mecachnically based car and aerodynamically based car so in an aerodynamic car which is something we've gone through in quite a lot of detail in the course already, this is something where we tend to be using the dampers for something a little bit artificial as far as control of the attitude of the car, controlling the angle of that floor with respect to the road surface both in terms of pitch and roll as well as the absolute ride height as well.

02:34

You can use the dampers to, it's almost like a cheating way of keeping the aero platform in that right ride height window whereas a mechanically based car, it's quite a different philosophy where you're much more focused on maximising the grip from the tyres.

02:49

So these two things are a little bit opposed to each other between the mechanical car and an aerodynamic car.

02:54

In an aerodynamic car, where you tend to be trying to optimise the underfloor aerodynamics because that tends to give you more of a performance benefit overall.

03:02

That ends up with the car generally being quite overdamped, particularly in rebound so this means that you're making a grip penalty in terms of your tyres so from a mechanical perspective you'll generally be in a lower damping regimen, certainly in the low speed area of the curves anyway, you'll generally be using a lower damping level in a mechanically based car versus an aerodynamic based car.

03:26

And that's certainly the example that we're going to be looking through today which I think is going to be applicable to most people taking this course is looking at optimising the mechanical aspects of the car as far as getting the most out of the tyres, rather than optimising the car for the aerodynamic platform.

03:41

I want to dive in a little bit deeper to a couple of the different aspects of both low speed and high speed damping here.

03:48

So if we're talking about low speed rebound which is any time where the damper is extending or the wheel is dropping with respect to the car.

03:55

So most of the time, the thing that we're going to be most concentrating on when we're going through a damper tuning process is what is happening with the inside tyres when we're rolling into a corner.

04:06

So the inside tyres are obviously, let's say we're turning left, these are going to be the inside tyres down here, sorry if I'm pointing this way here, so the inside tyres, the way we damp them in rebound is going to have a big influence on how much or how fast the car rolls as we roll into a corner.

04:24

That's really just controlling the speed at which the inside of the car is allowed to raise as the inside springs obviously try to push this thing up as we take the load transfer off them and transfer to the outside corners.

04:36

The outside sliders of the car, using those two inside dampers, that rebound is really going to control the rate of roll, certainly of the inside of the car.

04:45

On the other aspect there on the low speed compression side, what that's controlling is obviously the rate that the outside of the car drops which is going to happen to some extent as we load, take that load from the inside of the car to the outside of the car, that outside compression, the outside low speed compression is controlling the speed at which the outside drops and one of the things that you'll often get feedback from a driver on is by running more compression stiffness, more load speed compression, it'll tend to give the driver a better feel for how that outside tyre, whether it's the outside front or the outside rear, how quickly it's loaded in a corner.

05:22

So it can give some feedback as far as making the car feel more direct or maybe a little more, it takes driver input a little quicker and maybe feels a little crisper on the wheel.

05:32

Now if we start talking about the high speed bump regime instead, this is, as I said before this is where we're dealing with any irregularities in the track surface, curbs, anything that basically makes the damper move quickly in that high speed region.

05:46

So if we end up running a lot of high speed compression or high speed bump stiffness in the damper, that's going to mean that the car can tend to become quite harsh over the bumps so that means as each tyre gets to each bump in the road, it means more of that energy from the bump is transferred more quickly through the wheel, tyre, suspension, upright to the sprung mass and therefore the driver feels it as well.

06:08

On the other end of the spectrum, if you're running less high speed compression or less high speed bump stiffness, this can mean when you get to the bumps that the tyres end up, when you're travelling over these bumps, particularly if you're cornering at the time, the tyres can feel like they're traversing over top or skipping over top of these bumps.

06:27

They're not really biting down into it, they're just really skipping off each one as you go and what's happening there is when you don't have enough high speed bump control, that's more about the movement of the unsprung mass.

06:37

So as the chassis which is the part the driver's belted into, the chassis or the sprung mass might be relatively stable, if the tyre is skipping across the road surface, that's more about the natural frequency of the unsprung mass as it's skipping across the road surface in response to bumps so that might be a situation where you'd want to look at having more high speed bump control just to control that unsprung mass a little more.

07:03

Now the car we're using for the example today is one of our Toyota GT86 cars.

07:07

So this particular car has a MacPherson strut suspension in the front and it's got a multi link the rear and this is a circuit racing car, it's all it's really used for, it's not used on the road or anything like that, it's purely a racecar that gets used for a little bit of club racing.

07:22

The dampers we have in the car are MCA branded and they are part of their red line of suspension which is sort of a line of suspension that is more focused towards track cars rather than just street cars.

07:34

These MCA reds have only got a single type of damping adjuster on them so to relate that back a little bit back to what we talked about in the course, we talked about 1, 2, 3, 4 and even 5 way type adjuster dampers.

07:46

So this is a type of damper that sits in that first category of only single adjust.

07:51

Now normally when you've got a single adjust damper, normally the most dominant thing that you are adjusting is the low speed rebound.

07:59

There's always effects on other parts of the damping as well.

08:02

The amount of effect you get on different parts of the damping curves depends a lot on the anatomy of the damper and the design of the damper and how they're designing their different valves and everything like that.

08:12

But really it's usually the low speed rebound circuit that tends to be the most dominant.

08:16

If we just jump across to my laptop screen for a sec here I'll just orientate you guys a little bit to what these dampers actually look like.

08:22

So you can see in the middle here these are the front dampers.

08:25

So these are the MacPherson strut type which we can see which is really common when we have these two bolts mounted onto the lower mount there, that's the common MacPherson strut type attachment that you'll see in pretty much every Japanese car that's got a MacPherson strut.

08:38

And then on the outside we've got the rear dampers.

08:40

So these are part of a multi link where instead of having a rigidly bolted connected at the bottom like the MacPherson strut does, we've got these eye type attachments at the bottom and then a top hat as well.

08:51

Obviously we have in the front's a MacPherson strut, we have adjustable top hats as far as being able to make camber adjustments and stuff like that as well.

08:58

So looking from the top here we can see some of the different adjustment types I was talking about so here we see on the front dampers we have these sliding sections here which are obviously where one place we can make our camber adjustments on this car.

09:11

And down here these little red knobs on top here, these are the damper adjusters so these are the, this is the position where we make those adjustments just by turning those knobs and each time we turn one of those knobs, you get a little bit of a click.

09:23

I'm going to bring up the damper plots for this specific set of dampers that MCA were kind enough to share with us.

09:29

Before I do that I just want to orientate you guys and remind you guys a little bit more about how these damper plots work just by doing a couple of sketches here.

09:36

So if I was to draw a really simple damper plot here, essentially the two axes we have here, one is speed and remember this is the damper speed and on the vertical axis we have force or the force that the damper is providing us.

09:52

Now a couple of the really important things to understand when you're looking at a damper dyno plot like this is the convention.

09:59

What I mean by that is which direction is compression and which direction is rebound.

10:03

Now every damper manufacturer will tend to do this a different way so you'll always have to check.

10:08

Quite often they're labelled and sometimes they're not.

10:10

So all of the plots we're going to look at today, anything positive is going to be compression/bump just two words to describe the same thing.

10:20

And anything on the negative side of the plot down here is going to be on the rebound side.

10:27

So if we were looking at a curve that looked something like this.

10:34

That means this area here, let's say this is 25 mm a second here.

10:42

Anything in this area, or this quadrant, this is low speed compression.

10:49

Anything in this area here is going to be high speed compression.

10:52

Anything down here is going to be low speed rebound and anything in this section here is going to be high speed rebound.

10:58

So let's jump across to my laptop screen and have a look at the real damping plots of the actual MCA dampers.

11:04

So here I have the damping plots for both the front and the rear and I'm going to start with just the front, we can see this is just the front we're looking at here which is labelled.

11:13

We can see we've got our speed axis off here, this point down here is the zero point, so this zero velocity where all of these damping plots are intersecting and we can see one nice thing that MCA have done for us is they have labelled automatically the bump and the rebound sides of that plot so obviously this line here is our zero line, anything above this is going to be bump and anything below it is going to be rebound like we discussed before.

11:40

So again we are looking purely just at the front axle here and you can see we've got multiple lines on here, what do each of these mean? All of these are the different damping positions for this particular front damper.

11:50

So if we look down the legend in the bottom right here, we can see we have a whole lot of different numbers here, let's go through what they mean.

11:58

So this is another thing you've got to be careful of when it comes to dealing with adjusters on dampers, it's not only getting all over the convention that they're using for their plots but also understanding what their convention is for labelling each of their adjustments.

12:11

So the way MCA have labelled these here, and this is probably the way I find it more common to work, which is maybe a little counter intuitive for some people is that smaller numbers generally result in higher damping forces so in this case, the range of adjustment that MCA give is 12 clicks.

12:29

So that range runs from 0 to 12.

12:32

In this case zero is where you have the highest damping forces and 12 the highest number is where you have the lowest damping forces but either way, it's pretty clear when you go ahead and look at the plots themselves.

12:42

So we can see down here, let's just take some examples, if we were to look at 0, this number, the red line down here, if we look at the compression side, we can see that really clearly that this has the highest forces on that zero adjustment and then if we look at the highest number, the 12, we can see pretty clearly here, this is our number here, this is number 12, this is when we have the lowest forces.

13:05

Now the other thing to understand here is that they've only given us 0-6 in the adjustments and the skipped all the way to 12.

13:12

That's reasonable, it just means there's less damper runs for them to do when they're going ahead and testing this.

13:17

It's pretty reasonable at this point for us to interpolate between this point here which is line 6 and line 12, it's relatively easy for us to interpolate the difference between them but it's really in that 0-6 range where really the vast majority of the differences in the way the dampers are working is happening so let's go through a couple of those now.

13:38

So in the compression side we can see where we've got our stiffest settings up here.

13:42

We've got, really we've got low speed forces building really early, really quickly in the speed range.

13:49

I should just say as well here we've got, as far as the speed scale, you can see this first dotted line here which we can use as a reference, is happening at 50 mm/s so the almost arbitrary line that we use, well arbitrary reference point we're using from the course is 25 mm/s for low speed control.

14:05

Again I wouldn't get too hung up on that difference, it's just important you understand where people define their low speed boundary.

14:10

But just for reference, because that's 50 mm/s, that means roughly around this point here, this far into the graph, this is the point where we're transitioning from a low speed regime to a high speed regine.

14:22

So we can see from a compression perspective, this is really this damper is having a huge affect on the amount of low speed compression behaviour we've got as we change these clicks and we can see pretty clearly it's happening on both sides of the plot as well.

14:38

I said before normally things are most dominant on the rebound side when you've got a single adjuster, in this particular case we've also got a huge difference in the compression side as well.

14:48

Which depending on how you want to separate those things out, could be a good or a bad thing.

14:53

Either way it's good to have a lot of control over the ability to tune the dampers to where you need them to be.

14:59

So we can see here that as we move from 12 down to 6, we're really getting a big difference in how the damper is building its force.

15:07

You can see the slope of this line here which has a big effect on how the tyre behaves, how it's loaded when you add vertical load to it.

15:16

How quickly it's going to compress based on the slope of these lines in the low speed regime here.

15:22

And the other thing we can see which is really normal, which is part of our high speed relationship is as we go through and reduce these damping forces, so as we go from 0 to 1 to 2 to 3, each one of these lines here in the high speed regime is actually staying pretty much parallel and that's really what you expect to see off a single adjust damper like this, I'm not doing a very good job of sketching over top of those but hopefully you get the point that each one of those high speed lines is really staying parallel to each other.

15:49

The important thing to understand about these low speed adjusters when it's all on a needle and seat style adjuster which is almost always what you have in this low speed regime, is that we're only making changes to that initial slope of that low speed region, all the high speed adjustment, while we are controlling when the high speed circuit becomes active because each one of those lines is coming down like that, we're not controlling, we're not actually changing the slope of that high speed relationship line.

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16:15

So moving onto the rebound side here, arguably even though we have got a lot of bump control here, there is arguably a fair bit more going on on the rebound side as far as that adjuster, probably having more influence still on the rebound side even though we are getting quite a lot of bump control.

16:29

Now if we look at the first couple of clicks of adjustment here, so if we look at the red and the green, 0 and 1 down here, the interesting thing is if we look in the low speed section, these two lines are essentially lying right ontop of each other so straight away that means that there's not a huge amount of difference in the way the damper's behaving when we go from maximum damping just to that first click, certainly not in that really low speed region anyway.

16:53

It's not really until we get to that second click that position two which we can see down in the legend here which is this line here, where we start getting some sort of substantial difference and then by the time we get to position 3, we're really starting to have a lot of effect.

17:06

And this is relatively typical of what you'll see in the low speed circuits of all sorts of damper adjustments.

17:12

Things will tend to be, the clicks or those adjusters will tend to be more dominant in the lower end of the click range or when they're closer to their maximum settings.

17:19

And what's really going on there is because you've got a needle and seat type arrangement, it tends to be the most dominant because just because of the geometry of the needle and seat so when the needle's very close to the seat it's making big changes to the damping but once it starts opening up a whole lot more, it doesn't tend to, while it will make some changes, it doesn't tend to be as powerful a change.

17:41

So it's just important to understand that those first clicks close to maximum are the ones that tend to have the biggest changes on the performance of the car.

17:48

After than and then looking at the high speed change, so while we are dropping off in the high speed behaviour of the damper as we continue to lower the damping forces, we're getting that same behaviour here in rebound where really that slope is staying pretty constant in the high speed regime.

18:04

Obviously it's stepping down each time but the slope relationship is staying identical.

18:09

Now the other thing to understand here is that really looking at the front damper alone anyway, when we get down into the lowest damping setting, position 12 which is this light green colour here, we're almost really getting down into an almost linear style of damper which is not typically a style you'd see run in most modern mechanically based cars.

18:30

Really that completely linear relationship of the damping profile is not very common and as we'll see as we move through how we tune the dampers on this car, it's not an area where the car behaves particularly well.

18:44

It was much better in this area up here where you start to add more low speed control by getting some of these steeper curves before the damping forces then drop off.

18:53

So if we now move to the rear axle, we can see straight away what's really striking about this is that again the rebound is becoming much more of a dominant parameter compared to the compression.

19:06

We can just see that by the amount of spread down here that we've got in the low speed rebound settings versus the low speed compression.

19:13

Now I would say this is not an insignificant amount of bump or compression adjustment here, this is definitely still a significant difference in the way the rear axle's going to behave to compression forces.

19:25

It's just that the rebound is a much wider span so it's becoming a more dominant parameter as far as how the car is reacting to damping changes.

19:33

Now as I said in the course body, these plots shouldn't be taken in a way that's going to tell you necessarily how the car's going to behave when you put these dampers in your car.

19:42

The purpose of these plots really is to understand how the adjusters are working and to allow us to benchmark one damper vs another, whether that's taking the damper before and after it was rebuilt or just two dampers that are the same part number and we want to compare how they're working.

19:57

Or whether it's taking a new damper versus an old damper.

19:59

Now we can start to infer some differences about how we expect that to affect the car but it doesn't necessarily tell us a lot about how the car's actually going to behave with these dampers, it's really just more of a benchmarking tool.

20:11

The next thing I want to talk about is the role of log data versus driver feedback.

20:16

Now what I'm talking about when I'm talking about logged data for damping specifically is making use of damper potentiometers.

20:22

That's where we're measuring the amount of displacement that's happening with the damper in each corner of the car and from that you can infer a lot about the way the car's behaving.

20:30

Whether that's to do with the speed it's rolling at, how much the car's pitching at the front, what the ride height is as well as lots of stuff about how the actual dampers themselves are working, both in the time and the frequency domain as well.

20:42

So while making use of damping data is absolutely a useful tool, really the driver is the one that has the final say on what settings or what dampers are doing the best job in the car.

20:53

They're the ones in there feeling how the car responds, these are really complex devices, this is a highly transient environment, there's a lot going on and really the way the driver feels the car working really in my opinion anyway should be the final word on it.

21:07

The other thing to note here is that not everyone has access to the data logging equipment that you need to understand all of the damping data properly.

21:15

You need to have extra hardware as far as fitting these damper potentiometers to your car, you need to be logging them at a sufficiently high frequency, usually at least 500 Hz.

21:24

That in itself usually takes a relatively high end logger to be able to deal with those sorts of frequencies and a lot of logging memory, and on top of that you need the knowledge to be able to go through and analyse it for yourself.

21:34

Now that is something we cover in quite a lot of detail in our data analysis courses.

21:38

But for this course by itself, I'm willing to be that there's far more people out there that have adjustable dampers in their car than the people that have the ability to go ahead and log and analyse that data and use that to make better damping decisions.

21:53

So really the approach I'm going to take when we're talking about damping tuning today is going to be much more from the driver's perspective, how to go through and tune these for yourself on track based on what you feel from behind the wheel.

22:06

So the process I'm going to talk through today is all about trying different damping settings back to back and really the critical thing I want you to keep in mind both when you're looking at what we're doing today and when you're going ahead and doing this for yourself is you need to be as consistent as possible with the car in order to learn anything about what's actually happening with your dampers.

22:24

What do I mean by that? I mean things like, obviously you need to be doing all of your tuning on the same day at the same track.

22:29

You need to be using the same tyre set, ideally you need to be driving as consistently as possible, that usually means backing off your driving and not driving at 100% just to make sure you can drive as repeatably and consistently and have a little bit of spare brain capacity to think about how the car's actually responding to your inputs into these new settings each time you go out on track.

22:49

The dampers we have fitted to this car, obviously single adjust so if you were dealing with a damper with let's say 2, 3, 4 or even 5 adjusters, you can see really quickly how this blows up into a massive test matrix of different combinations of things to test on the car.

23:03

So the beauty of having just a single adjuster here is that we've got a little bit more of a narrow window of combinations we want to test on the car and that's the example I'm going to go through today and I think that's the example that's going to be most relevant to most people.

23:16

When you're thinking about how big you want to go between the steps between each adjustment, the thing that you want to keep in the back of your mind is that you do need to make sure that the steps you're making are going to be big enough to feel but you also don't want to be going every single click by click by click and doing run after run after run, simply because you're going to run out of consistency as far as you're going to run out of time on track, you're going to burn through a set of tyres or whatever it is.

23:39

Each damper manufacturer will have a different span or number of clicks that you can change the damper over as well as the valving and design of each damper is going to change how effective each one of those clicks or how much difference each one of those adjustment clicks is going to make to your actual damping profile.

23:55

The way we structure our testing for this set of dampers where we broke down things down into 5 runs.

24:00

So we have 12 clicks of adjustment there so that gives us 3 clicks of adjustment between each run.

24:07

So really that's probably a pretty sensible place to start is looking at, regardless of how many clicks you have in your dampers, you probably want to break this down into at least 5 runs to be able to go down in even steps throughout your damper profile to be able to make the steps big enough that you're going to be able to feel something on track but not going so small that you're going to need to do 10, 15, 30 runs on track to be able to cover the entire sweep of your damping profile.

24:30

My suggestion on how to approach this is to start with all 4 dampers on their lowest or their softest settings.

24:37

So that means all of the dampers clicked right down to their minimum damping forces and we're going to step up through them as we move throughout the test.

24:45

Now when you're on track, there are 5 main things that you want to think about how the car is responding on this particular run.

24:52

You want to think about the response of the car on corner entry, and what I mean by that is how the car rolls into the corner, how quickly, how stabily does the car roll into the corner? You want to feel how the car is feeling under braking, so how much is the front of the car pitching, how much is the rear of the car lifting? And how does that make the car feel as far as being settled or not.

25:12

You want to pay attention to the traction, particularly out of slow corners which is the place where you're going to be most traction limited.

25:19

This is all about understanding what the rear traction grip or in this case with a rear wheel drive car, what that traction grip is like and how the damping might be affecting that traction.

25:28

The last two points you want to concentrate on are understanding really how the car's behaving more in the high speed regime.

25:33

So the first thing is to understand if the car is starting to feel harsh over those bumps, so if you've got any bumpy sections on track, you want to think about how harsh one or both ends of the car are feeling as you traverse those bumps.

25:46

What I mean by harshness is you'll just feel a lot of really hard vibration through the car.

25:51

If it starts feeling harsh on a particular setting, you want to take note of that.

25:54

The last point you want to pay attention to is that feeling of the tyres and the unsprung mass skipping across any surfaces.

26:00

So this is really opposite to getting harshness.

26:02

If you don't have enough high speed control you'll end up in a situation where the tyres can start to float along the top of each surface so they get upset by the first one and they sort of skim along the tops of them rather than being able to drop back down and follow each different part of the road profile.

26:16

So those are the 5 different sections we need to be rating on each run.

26:21

After every run on track you want to be coming back to the pits and you want to be rating the car on those specific metrics that we've laid out there.

26:27

Having that structure around how the car's behaving is really important to get you specific things to look for on track.

26:35

The other thing is that even though you might be paying attention to these 5 metrics here, you'll also pick up all sorts of other useful and interesting things about how the car behaves differently on one damping setting to another that'll come out of this as well.

26:48

You'll also want to be ready to make notes on all of these as well.

26:51

This really brings up another point is I've talked about it before in this course where I think note taking is really important when you're going through and doing testing on your car, making sure you're organised with keeping all of your notes, being able to go back and refer to previous testing is a massive advantage and this is a great example of that.

27:09

Making a lot of detailed notes about what changes you made and what you felt in the car is going to be a really beneficial process when you want to go back and refer to these things later when you're looking at future damper tuning.

27:20

Before we get started with our runs, we want to make sure everything in the car is warmed up, now that doesn't just apply to things like the engine, the powertrain, the brakes and all that stuff, in particular what I'm most concerned about is making sure the tyres are up to temperature and up to pressure.

27:35

As I said before, we want all of our runs to be as consistent and repeatable as possible, we don't want, we want to keep all our different variables as controlled as possible.

27:44

So it's worth going out there and doing at least 1, maybe 2 warm up runs in that same profile I discussed before where you're going to do an out lap, you're going to do two fliers and then you're going to come in and do a slow in lap.

27:55

It's worth doing at least 1 or 2 of those, coming in, bleeding your tyres to target and then getting on and starting your testing.

28:01

This is all about making sure that first test run that we do when we're running the car on minimum damping is as useful as possible because it means that the car and the tyres will be up to temperature and pressure and it'll just make that comparison of that first run more useful as we move throughout the damping spectrum.

28:16

As you move throughout your test matrix, as you make comments and as you look at the lap times as you go, you'll start to build up a pretty rich picture of how the dampers are affecting the car in the first place.

28:27

Now this is a section of the car where people maybe tend to be a little bit scared about touching their dampers in the first place 'cause they don't understand exactly what they do or what effects they'll have on the car, hopefully this section of the course in general has given you a little bit more insight into that but you will find as you go through and make these changes, just actually going through the process of writing things down and looking at the way the car's behaving from those 5 metrics will start to teach you a lot about how the dampers are working in general.

28:54

When we're starting with the lowest damping settings, what you'll typically find is the car will feel quite floating and unsettled.

29:01

Now what I mean by that is when you go and turn into a corner and you're paying particular attention to the way the car's rolling into the corner, the car will feel like it doesn't have a very direct connection with the road and maybe it's rolling quite quickly as well.

29:14

Also once it gets to maximum roll, maybe you feel like it's actually oscillating a bit when it gets there.

29:19

The other thing is quite often when you're in the braking zone, you'll feel the front of the car dip really quickly, it'll drop really fast and that again can be quite unsettling because what often happens is the car, if you don't have enough damping you blow through all of the travel, suddenly you're hard down on the bump stops, it can end up in a situation where the car starts oscillating or losing some front grip, it can be a bit of an unpleasant feeling.

29:39

So what's going on there, when you're rolling into a corner it tends to be the rebound on the inside tyres that has a lot of effect of how the car rolls into the corner so that's really low speed rebound that's affecting that.

29:51

When it comes to the way the car is dropping when you're on the brakes, that's really the low speed compression on the front axle and to some extent the low speed rebound in the rear axle because it's not just the front of the car dipping, it's also the rear of the car raising that can give you some of the unsettled feeling depending on what sort of settings and wheel alignment you're running in your car.

30:08

One of the symptoms of having too much low speed rebound is that one end of the car tends to lose a little bit of grip on corner entry so we've harped on a lot in this course about how dampers are transient tools only, they're not something that controls the amount of how far something compresses in the end once you get to steady state, it's only controlling how fast it gets there.

30:29

So what do I mean by this? I'm saying if you get to a point of having too much low speed rebound in the front you might find you have some initial understeer on turn in or maybe if you have the other end of that spectrum, some initial oversteer on corner entry you might have too much low speed rebound in the rear.

30:48

What you'll generally find is the end that has too much rebound damping on corner entry is the end that will tend to break away first.

30:55

When you've got insufficient bump or compression damping, that's where you're going to start feeling the car start to float across some of those unsettling parts of the track so that's not something you're looking for in smooth sections of the track, it's only in those bumpy areas.

31:07

On the other end of the spectrum when you've got too much compression or bump damping, that's when you'll feel that harshness that we've talked about a couple of times before.

31:13

So after going through this matrix of tests and reviewing your notes, your feedback, your lap times, you're already going to have a pretty good idea of what sort of position in your damping range you want your car to operate in to get the most out of it or at least to start as a baseline setting before going ahead and zoning in a little bit more and doing some more detailed damper tuning.

31:32

Just going through this process, this test matrix will already teach you a lot about the way your dampers are working in your car.

31:39

So for a relatively simple style of damper with a single adjust like this and a mechanically based car, what you generally want to aim for is you'll get to a point where you've stopped seeing gains in response and you generally want to come back a little bit from those maximum settings, you generally want to be on the slightly lower side of damping than the slightly higher side when we're talking about mechanically based cars.

32:01

So what do I mean by that? Let's say one of your main metrics you're looking to improve in your car is the way the car turns into corners, the way it takes a set, the way it rolls into corners.

32:10

Let's say you get to a point halfway through your damper tuning where maybe you're not feeling any more gains on that, it's not getting any better, that's usually an indication where some of that low speed performance, you're not making any gains in that, that's usually a point where you start to want to get the maximum point of that and come back maybe a little bit, half a step or something like that.

32:29

You generally if anything want to err on the lower side of damping than the higher side, generally what that's about is reducing that contact patch load variation of the tyres.

32:39

In general, particular low speed rebound, any additional low speed rebound will tend to start hurting your contact patch load variation which will hurt your overall cornering and grip power in general so just something to keep in mind, when you stop feeling gains in any particular direction in that damping matrix, that's probably a situation where you want to note when that happens and maybe just back it off a step or half a step from that position.

33:04

Now so far everything we've talked about has been moving all of the damping front and the rear all 4 corners in the same direction the same amount each time.

33:11

So we started with minimum damping then we've gone plus 3 clicks and plus 3 clicks and plus 3 clicks and every time we're doing one of those clicks in the dampers, we're doing in all 4 corners at the same time.

33:20

Once you have got to the position where you are happy with the car, you'll have some optimum setting whether that's by feeling or lap time or ideally both, then that's a situation where you can start just tuning one end of the car at a time, dialling one end in relative to the other.

33:37

It's very unlikely it's going to be the case that going up and having the same settings at both ends of the car is going to be optimum for that car and that track and you, everything like that, it's going to be more of a case of wanting to tune each end individually but it's usually most helpful to get the whole car in the window by going up in these simple steps first before you start dialling and carrying out that same process at the front and the rear.

33:58

Now I'm going to come back and talk about that in a bit more detail.

34:01

I'm going to use the real example of tuning our GT86 with that same process I've just gone through and just talk through some of the driver feedback and how we found the optimum damping settings for this car.

34:11

So here I'm just going to talk through all of our 5 runs, reading out the driver feedback as I go just to understand how these adjustments related to what the driver feedback was.

34:18

So here on run on1, we are on minimum damping so that is all 4 dampers set to their minimum or their softest settings.

34:27

Driver feedback for run 1, car was wallowing on corner entry, did not feel positive at either end.

34:32

Did not feel settled, felt like it was surfing over the bumps, front also diving a lot under brakes.

34:39

Now all of that feedback is pretty consistent with what we have discussed already with what you might expect on a car with not enough damping.

34:46

Run 2, this was plus 3 clicks so this is the first adjustment of increasing the damping so we're position 3 here.

34:53

Big improvement from full soft, car much more direct at turn in, settled better and took a set in the corner.

35:00

Front felt more secure under braking, didn't dip so much, felt like car followed the bumps better.

35:06

So already sounds like a pretty big improvement from our minimum damping settings there.

35:10

So let's move on to run 3, we're making an additional 3 clicks all around to increase all of our 4 dampers at the same time.

35:17

The driver feedback for run 3 was small difference to previous run, felt a little sharper overall, can start to feel the bumps a little bit more overall but not a problem.

35:27

Braking felt no different.

35:29

So what we're finding there is maybe a small difference in the way the car's taking a set into the corner but maybe not massive.

35:35

He is starting to notice the way the car's behaving over the bumps, starting to feel a few more of them in the car but no change in the way the front's diving under braking so that's important to note.

35:45

Run 4 which is an additional 3 clicks again, feedback was feels a bit better on turn response again, sharper overall.

35:53

Starting to get a little bit more upset over the bumps but not a concern, traction starting to suffer out of the hairpin.

35:59

So this is interesting here because again we're starting to find some small increases in our turn in response and how the car's taking a set in the corner which the driver feedback seems to be positive out of.

36:10

The car is starting to get a little bit more upset over bumps and they're saying here that while they're starting to feel it more, they don't feel it starting to upset the car, it's not doing anything bad so we can deal with that, that's fine but it is really important to note here that the traction is starting to suffer, this is obviously a rear wheel drive car, they're struggling with traction out of a slow corner here so that probably starts to indicate we're starting to get out of the window a little bit on the rear damping in particular here.

36:35

Now the last run here, run 5, this is another plus 3 clicks all around, we are now set at the maximum damping all around for this set of dampers.

36:43

No difference in corner entry phase, didn't notice any difference in the sharpness.

36:48

Had to back off a little bit over the bumpy sections and lost some time there.

36:52

Getting too hard to control now, low speed traction worse again.

36:56

So we're really finding pretty consistent trends here, in that our turn in response and our cornering, the way the car's taking a set in the corner, really they haven't noticed any difference in this run which is important to note so we haven't really made any gains there.

37:09

But they are saying, now the car is getting a little bit difficult to manage over the bumps when they feel like they're losing some time there and the low speed traction or that traction out of the low speed corners is starting to suffer even more so it's a really good learning straight away there.

37:26

So the way I'd summarise that is probably somewhere between run 3 and run 4 it's probably starting to get pretty close to a good baseline for this car, that's when we started to get diminishing returns on the way the car was entering the corner and taking a set before we started to create big problems with the car being upset over bumps and starting to hurt traction out of slow corners.

37:45

So this gives us a baseline of position 6 which is roughly halfway in our damping click range so roughly half of that full range.

37:53

Let's have a look at our damping plots again just to see exactly how that relates, what that actually means.

37:59

So looking at the plot here for position 6 which we can see down here.

38:02

So we're roughly in this area here, this brown line that's following through here on the damper plot, so that's where currently, for the current baseline, the front of the car is the most happy.

38:13

Now if we go to the rear and we look at the same thing, it's exactly the same colour convention so on the compression side in the rear we're on this line here and on the rebound side we are on this line here.

38:25

So now we've got a good baseline for the whole car as one where we've gone through in equal steps on both front and rear dampers in the same adjustment amount each time.

38:33

Now we're ready to go back and iterate a little bit around individually at the front and the rear axles.

38:38

So what we did, we took our baseline position of 6 on the rear axle and we're going to go back and forward either side of that to try and find a few more gains.

38:46

Now what we found was when we went down in the rear axle the car felt a little bit more floaty on damping on entry to the rear and when we went up again it started to pick up some of that harshness through the bumps so in the end, it actually ended up staying at that initial position 6, halfway in the damping spec was the best setting for the rear axle.

39:08

Now conversely we did the same test on the front, so we stayed at our baseline position 6 on the rear which was our optimum rear setting and we did that same thing, we went either side both to 9 and 6 so more and less damping.

39:20

Well in this case 3 would be less damping and 6 would be more damping because of that damper convention of higher numbers being lower damping levels.

39:28

Either way, having more damping on the front axle, that actually ended up helping the front axle.

39:34

So this is where it's really important to understand that we need to start diverging and doing the front and the rear separately, you can only learn so much by doing all of them together.

39:43

So in this particular situation our optimum setting was having a setting of 3 on the front which remember was 0 being the maximum so we went from 6 to 3 on the front which was where the front was feeling the happiest and this was really coming fromt he way the car was turning into the corner, the way it was taking a set, we were still able to find a few more gains by running the front a little bit higher and leaving the rear a little bit softer by running those lower baseline settings of 6 so we had a setting of 3 in the front and a setting of 6 in the rear.

40:11

Remembering it was 0 being the maximum damper setting.

40:14

So this was the process for how we tuned in the dampers on that GT86 and hopefully you can see there by applying that process to pretty much any car that's got a single adjustable damper or if you've got more sophisticated dampers that just expands your testing matrix out a little bit.

40:29

The process is going to be exactly the same.

40:31

Now that we've got that baseline setting for that car, what we'd typically do is each time we head to a separate track, if we've got time to do some more testing at that track we would tend to iterate around either side of our baseline and see if one particular circuit tends to like a different damping setting compared to our baseline.

40:48

Typically you will find changing your damper settings per circuit is usually a good way to go.

40:53

You've usually got different road surface profiles, different tyre energy inputs, there's all sorts of different parameters that affect the sorts of damping we need to run but it is worth always going ahead and playing around your baseline settings but making you're always taking your notes as you go because invariably these are really useful learning as you go.

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