Body Roll

[clakka]

hey all,

Quick and probably silly question but I will ask anyway.

I have just bought some new coilovers - G4 from just Jap with spring rates of 7 and 5. This is my 1st set of coilovers and before I purchased them I was under the impression that coilovers virtually eliminated body roll. I must admit that the handling feels better but it is nothing like I thought it would be.

There is still a large amount of body roll and the tail end doesn't seem to 'swing' around to meet the front like I thought it would.

Have I been totally deluded to think coilovers would 1. remove body roll and 2. make the tail more 'trigger happy' or have I chosen the wrong spring rates.

Secondly, if this is how they are supposed to be should I invest in a rear strut brace or something else to assist the removal of the rolol???

Thanks for the help.

Clakka

[Roy]

How long is a piece of string? Take it to your local suspension place and get them to check your ride height and wheel alignment. Thats the best place to start.

[Simon-S14]

rear strut barce will do SFA

What you need is upgraded sway bars! Sway bars control roll, not the shocks and springs .

[RBwhatever]

Sway bars will fix your roll problem.

[Ronin 09]

they're heavy spring rates - do the shocks actually control the springs well?

what car?

swaybars will control roll

[Simon-S14]

they're heavy spring rates - do the shocks actually control the springs well?

what car?

swaybars will control roll

they are D2/G4's or whatever... so no, they dont

[Roy]

Swaybars will help control roll. Help. Those spring rates arent exactly low. On road tyres i would expect it to be quite a firm/tight ride. Get a good alignment and make sure the shocks are set to the right heights. Remember stiff as buggery doesnt mean grip/good. It may be what you liek seat of the pants but may not equate to a good handling/balanced car

[Duncan]

well......stiff springs also control roll so its not that simple.....

[260DET]

If the ride height has been lowered then the roll centers will be lower too, which means you will need stiffer ARB's. Lower roll centers = more body roll, all else being equal.

[Sydneykid]

It's a bit more complex than simple spring rates.

What determines roll is the difference between the centre of gravity (CoG) and the centre of roll (roll centrre or RC). This difference is called the roll couple (RC). The larger the RC the more the body rolls. When you lower a Skyline too far, the roll centre moves downwards more than the CoG. So you are increasing the RC and therefore increasing the body roll.

This is a spiral, the lower you go the higher the spring rate needs to be to counteract the chassis' new found propensity to roll. That's one of the reasons (not the ONLY reason) why Jap coil overs have such rediculously high spring rates. Their typical customer wants a low rider, so they have to use out of proportion spring rates to overcome the body roll isuues created by that low ride height. They also use high spring rates because there simply isn't enough suspension travel to absorb bumps, so they jack up the spring rate to stop the shock compressing over bumps. In addition upgrading stabiliser bars is a bit of a lost art to the typical Japanese upgrader, so they use high spring rates to control the roll that is really the stabiliser bars job.

The answers are simple, don't lower it too far (around 350 mm front and 340 mm rear is the best for handling while retaining some ride comfort) and use the parts that are designed to do the job (ie; use stabiliser bars to control the roll).

It is worth mentioning that the outside tyres themselves compress under cornering loads, so you need to think about whether the body roll you are feeling is not in fact tyre compression.

cheers