BMW M3 Forum (E90 E92)

BMW Garage BMW Meets Register Search Today's Posts Mark Forums Read


Go Back   M3Post - BMW M3 Forum > E90/E92 M3 Technical Topics > Track / Autocross / Dragstrip / Driving Techniques
 
Post Reply
 
Thread Tools Search this Thread
      10-16-2012, 05:52 PM   #1
Ross_Bentley
New Member
0
Rep
5
Posts

 
Drives: MINI Cooper S (& someone's M3)
Join Date: Sep 2012
Location: Issaquah, WA

iTrader: (0)

Shock tuning thoughts...

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.
__________________
Driver coach, author of Speed Secrets books & publisher of Speed Secrets Weekly inbox magazine
http://speedsecretsweekly.com
http://www.DriverCoach.net
http://www.facebook.com/Drivercoach
Appreciate 0
      10-16-2012, 07:03 PM   #2
MKE_M3
Lieutenant Colonel
MKE_M3's Avatar
United_States
23
Rep
1,688
Posts

 
Drives: 2011 e90 M3
Join Date: Feb 2009
Location: Milwaukee, WI

iTrader: (0)

Interesting thoughts, thanks for sharing!
__________________
Appreciate 0
      10-16-2012, 08:23 PM   #3
klammer
Brigadier General
41
Rep
3,245
Posts

 
Drives: 11 spc gry m3 e90, 07 X5
Join Date: Jan 2010
Location: chicago

iTrader: (0)

Quote:
Originally Posted by jdemetry
Interesting thoughts, thanks for sharing!
Yes! Thank you
__________________
mods: akra evo, dinan 3.45 diff, ess akra tune, dinan stg.3, Alcon bbk, HRE P40
Appreciate 0
      10-16-2012, 10:01 PM   #4
bigjae1976
That's what she said...
bigjae1976's Avatar
84
Rep
5,648
Posts

 
Drives: 11 E90 M3 Individual
Join Date: Mar 2006
Location: Milwaukee, WI

iTrader: (12)

Garage List
2004 BMW M3  [4.50]
2011 BMW E90 M3  [5.00]
2013 BMW 328i  [5.00]
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
__________________


Sponsored by Momentum BMW #593...We Bleed BMW BLUE!

Last edited by bigjae1976; 10-16-2012 at 10:12 PM.
Appreciate 0
      10-17-2012, 01:26 AM   #5
rzm3
Moderator
rzm3's Avatar
224
Rep
4,603
Posts

 
Drives: E92 M3
Join Date: Aug 2007
Location: USA

iTrader: (14)

Great explanation! Here's a chart regarding this topic. http://www.m3post.com/forums/showthread.php?t=735413
__________________
E92 M3 DCT - AiM EVO4 Data Logger / AiM SmartyCam HD / KW Competition 2-Way / OMP ARS Racing Seats / Brembo GT 365 / Pagid Yellow RS-29 / Rear Seats Delete
Appreciate 0
      10-17-2012, 10:03 AM   #6
bigjae1976
That's what she said...
bigjae1976's Avatar
84
Rep
5,648
Posts

 
Drives: 11 E90 M3 Individual
Join Date: Mar 2006
Location: Milwaukee, WI

iTrader: (12)

Garage List
2004 BMW M3  [4.50]
2011 BMW E90 M3  [5.00]
2013 BMW 328i  [5.00]
Quote:
Originally Posted by RLDZHAO View Post
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.
__________________


Sponsored by Momentum BMW #593...We Bleed BMW BLUE!
Appreciate 0
      10-18-2012, 12:25 AM   #7
JAJ
Captain
17
Rep
933
Posts

 
Drives: 2014 Shelby GT500
Join Date: Apr 2008
Location: Vancouver, BC

iTrader: (4)

Quote:
Originally Posted by Ross_Bentley View Post
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.
Appreciate 0
Post Reply

Bookmarks

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -5. The time now is 06:03 PM.




m3post
Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
1Addicts.com, BIMMERPOST.com, E90Post.com, F30Post.com, M3Post.com, ZPost.com, 5Post.com, 6Post.com, 7Post.com, XBimmers.com logo and trademark are properties of BIMMERPOST