Rebound and bump for idiots

daniel · 24-11-2009, 07:35 AM

Hi,

There appears to be a lot of experience with KW suspension on this forum so I thought I would pose the question... how does bump and rebound affect my ride quality.

I have read the pdf on thorney website but am having trouble relating to real world and my setup. For example, the pdf suggest rebound impacts dive and roll, whereas I thought softening off my compression (bump) would result in a great weight transfer, and ultimately grip?

Which setting has the greatest impact on ride comfort? ie help soaking up bumps and ridges while just cruising?

Thanks

**shimmy** · 24-11-2009, 07:53 AM

Quote:

Originally Posted by sunnybono

Hi,

There appears to be a lot of experience with KW suspension on this forum so I thought I would pose the question... how does bump and rebound affect my ride quality.

I have read the pdf on thorney website but am having trouble relating to real world and my setup. For example, the pdf suggest rebound impacts dive and roll, whereas I thought softening off my compression (bump) would result in a great weight transfer, and ultimately grip?

Which setting has the greatest impact on ride comfort? ie help soaking up bumps and ridges while just cruising?

Thanks

Most effective way of improving ride quality is by......

Going back to OEM as KW has a poor range for road settings

Thorney · 24-11-2009, 09:19 AM

lol.

I'm writing an article for a magazine about car set up so the full detail will have a wait (its a 5 page article) but in essence:

Spring - holds the car up and combined with ARB controls some aspects of the cars roll, stiffer spring means car will roll less but means it will take more of a bump to get it to compress (I wont go into progressive rates etc).

Compression (bump) damping - controls the speed at which the shock compresses when hitting a bump in the road, on 3 way suspension this is split between high speed and slow speed. High speed means high speed compression, ie hitting a kerb, slow speed is more transissional; undulations in the road. So, if you have a ride where the car feels too crashy over bumps then its likely your bump is too hard and needs to be softer. However if you go too soft the chances are the spring is too hard for your needs and you're better off changing a spring rather than running damping on full soft.

Rebound damping - this controls the speed the shock extends after compression, rebound tends to control the speed at which the car retains its balance, if the car feels bouncy the chances are the rebound is too soft and is reacting too quickly so you need to stiffen it up.

Add in tyres, wheels, ARB's, ride height, camber, castor, trail, toe, mono tube/twin tube, aero and driver style and you can see why it takes some time to really develop suspension for road or track. In development we tend to use three way adjustable (4 way sometimes buts its hard work) to set up damper settings which are then used on the less adjustable shocks for the road. Takes me 2 full days to set up a race car from scratch on three ways for example and assumes about three spring rate changes.

Thorney · 24-11-2009, 09:24 AM

There is also no 'right' answer, I tend to prefer very stiff springs and very soft damping as (IMO) it allows greater adjustment of grip over a wide range of applications, but other people prefer a very soft spring and very hard damping, its a case of whatever works for you.

Generally soft = grip but it comes at the expense of overall speed.

**glendog74** · 24-11-2009, 01:20 PM

Quote:

Originally Posted by shimmy

Most effective way of improving ride quality is by......

Going back to OEM as KW has a poor range for road settings

Rubbish...

And you have had first hand experience of KW Shim?

Curly · 24-11-2009, 01:25 PM

he's pulling yer chain snoopdog

**shimmy** · 24-11-2009, 01:27 PM

Quote:

Originally Posted by glendog74

And you have had first hand experience of KW Shim?

yep

**glendog74** · 24-11-2009, 01:33 PM

Quote:

Originally Posted by dontdobends

he's pulling yer chain snoopdog

Most probably - as Shimmy always does...

Quote:

Originally Posted by shimmy

yep

Go on then, tell me all about your personal experience of KW V3's or Clubsports as fitted to your M3 CSL & why there isn't enough adjustment...

daniel · 24-11-2009, 07:13 PM

Thanks for the help

So bump will infact control things like rear end squat and diving under braking.

Based on no experience at all I would have thought that a soft to moderate bump and harder rebound would suit our roads?

**shimmy** · 24-11-2009, 07:41 PM

Quote:

Originally Posted by glendog74

Most probably - as Shimmy always does...

Go on then, tell me all about your personal experience of KW V3's or Clubsports as fitted to your M3 CSL & why there isn't enough adjustment...

not my CSL but the M3 i drove with KWV3, the only criticism i found was there didnt seem to be enough adjustment to get it compliant enough for the road anywhere near OEM or as much as Intrax. It seemed to still be a bit lumpy and thumpy which i was not used to

Now i know the springs might have been different but that was my experience

24-11-2009, 07:35 AM	#1
daniel S4 - Getting the hang of it Join Date: Sep 2009 Posts: 247 Casino cash: $11332	Rebound and bump for idiots Hi, There appears to be a lot of experience with KW suspension on this forum so I thought I would pose the question... how does bump and rebound affect my ride quality. I have read the pdf on thorney website but am having trouble relating to real world and my setup. For example, the pdf suggest rebound impacts dive and roll, whereas I thought softening off my compression (bump) would result in a great weight transfer, and ultimately grip? Which setting has the greatest impact on ride comfort? ie help soaking up bumps and ridges while just cruising? Thanks

24-11-2009, 09:19 AM	#3
Thorney S5 - Full Throttle Join Date: Sep 2007 Posts: 469 Casino cash: $3876	lol. I'm writing an article for a magazine about car set up so the full detail will have a wait (its a 5 page article) but in essence: Spring - holds the car up and combined with ARB controls some aspects of the cars roll, stiffer spring means car will roll less but means it will take more of a bump to get it to compress (I wont go into progressive rates etc). Compression (bump) damping - controls the speed at which the shock compresses when hitting a bump in the road, on 3 way suspension this is split between high speed and slow speed. High speed means high speed compression, ie hitting a kerb, slow speed is more transissional; undulations in the road. So, if you have a ride where the car feels too crashy over bumps then its likely your bump is too hard and needs to be softer. However if you go too soft the chances are the spring is too hard for your needs and you're better off changing a spring rather than running damping on full soft. Rebound damping - this controls the speed the shock extends after compression, rebound tends to control the speed at which the car retains its balance, if the car feels bouncy the chances are the rebound is too soft and is reacting too quickly so you need to stiffen it up. Add in tyres, wheels, ARB's, ride height, camber, castor, trail, toe, mono tube/twin tube, aero and driver style and you can see why it takes some time to really develop suspension for road or track. In development we tend to use three way adjustable (4 way sometimes buts its hard work) to set up damper settings which are then used on the less adjustable shocks for the road. Takes me 2 full days to set up a race car from scratch on three ways for example and assumes about three spring rate changes. __________________ http://www.thorneymotorsport.co.uk

24-11-2009, 09:24 AM	#4
Thorney S5 - Full Throttle Join Date: Sep 2007 Posts: 469 Casino cash: $3876	There is also no 'right' answer, I tend to prefer very stiff springs and very soft damping as (IMO) it allows greater adjustment of grip over a wide range of applications, but other people prefer a very soft spring and very hard damping, its a case of whatever works for you. Generally soft = grip but it comes at the expense of overall speed. __________________ http://www.thorneymotorsport.co.uk

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24-11-2009, 01:25 PM	#6
Curly S5, Sport On, DSC M-track Join Date: Sep 2007 Location: madchester Posts: 1,153 Casino cash: $5838	he's pulling yer chain snoopdog

24-11-2009, 07:13 PM	#9
daniel S4 - Getting the hang of it Join Date: Sep 2009 Posts: 247 Casino cash: $11332	Thanks for the help So bump will infact control things like rear end squat and diving under braking. Based on no experience at all I would have thought that a soft to moderate bump and harder rebound would suit our roads?