Shock tuning thoughts...

[Ross_Bentley]

Over the past couple of months I've had more drivers ask about how to tune their car's shocks than just about anything else (and I get dozens and dozens of questions every month sent to me...). So, to answer as many as I can at one time... While I'm not an engineer, nor claim to be an expert on shocks, I've been fortunate enough to work with some amazing engineers who have taught me a lot over the years (Jeff Braun being the very best). In putting together a shock tuning eBook lately I've also thought a lot about priorities, and if I had to pick just 3 things that drivers should know, these would be them:

1. Shocks are timing devices - they speed up or delay what the car is going to do in terms of a handling characteristic. In other words, if your car is going to understeer in the middle of the turn when it's taken a set, tuning the shocks will not help that all - the car is in a steady state at that moment and the suspension geometry, aerodynamic balance, tires and pressures, springs and anti-roll bars control the steady state handling. What tuning the shocks might be able to do is make the understeer start earlier or later in the turn, and if you delay the onset of the understeer long enough you might be at the point where you're now unwinding the steering wheel and it no longer is a factor. In doing this it may have seemed you eliminated the understeer, but in reality you delayed it until it no longer mattered. So, use the shocks to slow down or speed up a specific handling characteristic. If the car is rolling too much, you can only slow down how much it rolls with the shocks, not how much (that's the springs and anti-roll bars' job).
2. If you have high-speed and low-speed adjustments on your shocks, understand the high-speed mostly deals with how your car responds to track surface irregularities (bumps, cracks, etc.) - it impacts the harshness of the ride. Your low-speed adjustments control the handling of the car. And just to clarify, high-speed and low-speed have nothing to do with how fast your car is traveling - it's the speed of the shock's shaft movement. High-speed is when a bump causes the shock to compress quickly; low-speed is when the shock's shaft is moving more slowly from roll and pitch in the car (handling issues). So, use low-speed adjustments to control the handling, and high-speed to control ride. This is a general rule, so it doesn't always apply.
3. Make only one change at a time. If you make two changes to your car and then go out and it's better, how do you know which one made it better?

Again, this is general advice that doesn't always apply, but does most of the time. And, did I mention I'm not a shock engineer?!! But if you stick with this advice you can't go too far wrong. Of course, you can hire a real shock expert and that will do more good than just about anything else.

[MKE_M3]

Interesting thoughts, thanks for sharing!

[klammer]

Originally Posted by jdemetry

Interesting thoughts, thanks for sharing!

Yes! Thank you

[bigjae1976]

You basically answered what has been an unanswerable question here on this forum and also at the track. While the DE org I usually run with is top notch they never really get to the point beyond basic alignment setups.

I have double adjustable Koni's. I just guessed at both settings. Maxed the rebound and around 1/2 on the compression. There was no science beyond the fact that I turned up the rebound until I would no longer bounce out of my seat going over a bump.

Thanks! And what an honor to have you on this forum.

EDIT: An honor to have Ross...not Klammer

[rzm3]

Great explanation! Here's a chart regarding this topic. http://www.m3post.com/forums/showthread.php?t=735413

[bigjae1976]

Originally Posted by RLDZHAO

Great explanation! Here's a chart regarding this topic. http://www.m3post.com/forums/showthread.php?t=735413

Rich, that was a great post and I was about to look for it. To me, your flowchart was like a foreign language. I think when you look at what Ross said and THEN look at your flow chart it makes much more sense. With some self study, I can now logically think through the issue and then apply a solution.

Although I'm very happy with my E46s handling. And I used a much better and easily understood method...guestimation.

[JAJ]

Originally Posted by Ross_Bentley

Over the past couple of months I've had more drivers ask about how to tune their car's shocks than just about anything else (and I get dozens and dozens of questions every month sent to me...). So, to answer as many as I can at one time... While I'm not an engineer, nor claim to be an expert on shocks, I've been fortunate enough to work with some amazing engineers who have taught me a lot over the years (Jeff Braun being the very best). In putting together a shock tuning eBook lately I've also thought a lot about priorities, and if I had to pick just 3 things that drivers should know, these would be them:

1. Shocks are timing devices - they speed up or delay what the car is going to do in terms of a handling characteristic. In other words, if your car is going to understeer in the middle of the turn when it's taken a set, tuning the shocks will not help that all - the car is in a steady state at that moment and the suspension geometry, aerodynamic balance, tires and pressures, springs and anti-roll bars control the steady state handling. What tuning the shocks might be able to do is make the understeer start earlier or later in the turn, and if you delay the onset of the understeer long enough you might be at the point where you're now unwinding the steering wheel and it no longer is a factor. In doing this it may have seemed you eliminated the understeer, but in reality you delayed it until it no longer mattered. So, use the shocks to slow down or speed up a specific handling characteristic. If the car is rolling too much, you can only slow down how much it rolls with the shocks, not how much (that's the springs and anti-roll bars' job).
2. If you have high-speed and low-speed adjustments on your shocks, understand the high-speed mostly deals with how your car responds to track surface irregularities (bumps, cracks, etc.) - it impacts the harshness of the ride. Your low-speed adjustments control the handling of the car. And just to clarify, high-speed and low-speed have nothing to do with how fast your car is traveling - it's the speed of the shock's shaft movement. High-speed is when a bump causes the shock to compress quickly; low-speed is when the shock's shaft is moving more slowly from roll and pitch in the car (handling issues). So, use low-speed adjustments to control the handling, and high-speed to control ride. This is a general rule, so it doesn't always apply.
3. Make only one change at a time. If you make two changes to your car and then go out and it's better, how do you know which one made it better?

Again, this is general advice that doesn't always apply, but does most of the time. And, did I mention I'm not a shock engineer?!! But if you stick with this advice you can't go too far wrong. Of course, you can hire a real shock expert and that will do more good than just about anything else.

Ross - thank you! for your well-crafted and crystal-clear post on this usually vague and poorly understood topic. The way I've explained it is pretty much the same as you do - high-speed damping controls sudden movements of the wheels relative to the body (think curbs and bumps), while low-speed damping is about the movement of the chassis relative to the ground (think driver inputs like turning and braking).

The most important thing that low-speed damping does is control how quickly weight transfers from the rear to the front under braking and from the inside to the outside wheels on turn initiation. The stiffer the settings, the faster the weight moves. That improves grip, at least up to the point where it's transferring so quickly that the handling becomes unstable.