Hi all, hoping to get some input from those of you who race.

My car is purely for race use.

Weight is 1020kg (2250lbs) without me in it but with fuel.

I have Nitron 2 way adjustable dampers with 650lb front and 600lb rear spring rates. I currently have the OEM (MY05) ARBs on the car.

Diff is a Kaaz 1.5 way set to 30% lock.

Tyres are A048 semi slick with -3 deg front and -2.5 deg rear camber. 0.2 deg total rear toe.

APR 200 wing.

Ran all last season with 650lb front and 750lb rear springs with OEM bars and whilst I had no roll / squat / dive, it was very twitchy at the back with power oversteer, as you an imagine!

So i'm hoping that the much reduced rear spring rate will improve oversteer issues, but i've not driven the car yet.

I have a set of ARBs I can put on, which are a Saner front (3 position adjustable) and a Whiteline rear which is about 50% stiffer than OEM.

My question really is whether to put the aftermarket ARBs on. I'm guessing that even though my car is light, the soft rear springs are going to cause some roll at the back where the real aim of putting the soft springs on was suspension compliance. So if I put the Whiteline rear bar on to prevent roll, i'm going to need to put the stiffer front on to match.

Thoughts on whether putting the ARBs on is going to make things too uncompliant would be appreciated.

IIRC quite a few in the US are running similar spring rates / with Saner ARB?

 

For US readers: ARB = anti-roll bar = sway bar

 

 

I'd recommend an adjustable bar with roller bearings.

 

Roller bearings in a Sway Bar application are a bad idea. Ask any Bearing engineer. I did.
Sway bars have a limited range of motion which is very unfriendly to roller bearing balls and races.
Don't do it.

Roller Bearings are made to run on 360 degree rotation applications. This is how they get the required lubrication. Also after taking a significant loaded hit they deform and the only way they will regain their shape as a sphere is to rotate 360.
Unlike bushings they cannot be acquired in a self aligning configuration and will therefore bind with chassis flex causing rate variability.

Self aligning Bushings are what you want. This is what race cars run. Bronze is good.

On the Sway bar questions use your Saner. You already have it. Run it full soft and use the OEM bar in the rear. Are you running 255 square? I would run the -3 to -3.2 all around.

Try that first.

 

I'm running a Comptech adjustable front sway bar with the provided standard bushings so I have no direct experience with roller bearing sways but the latest trend is 3 piece splined bars with roller bearings. They're popular with the NASCAR circle track guys but perhaps the bearings are a regularly replaced wear item.

 

Id drive the car with the new spring rates first, then go from there. One variable at a time.

FWIW, a lot of the fast NASA TT guys here in the midwest run 700/600 or 700/650 springs on stock sways.

 

I like the OEM rear bar and some kind of front bar that's a bit stiffer than stock but not crazy. I don't run aero either though and I imagine if I did I'd want less front sway.

 

Thanks Mark.

I have put the Saner on the front on the soft setting. Rear I went with the Whiteline but did think of leaving the OEM one there. Can't remember what the rate of the 05 one is...

I have 235/45 up front and 255/40 at the rear, hence the cambers i'm using are more at the front. Wear pattern is perfect.

 

Probably true, too late now though

They are pretty easy to change so will see how I get on.