rake adjustment for traction

[kyleb]

I believe this post belongs here. Correct me if I'm wrong.
first thing, I have an open wheel car. It is not an Atom, but very similar as far as specs go.
I research Atoms a lot because it is really the best comparison to look at to avoid reinventing the wheel.

What are the factory ride height setting on an atom? Specifically the amount of rake if any? I'm not looking for a particular year model atom, but I guess the latest may be the greatest.

I am curious because I am wondering if rake can effect rear wheel traction. Straight line or turning traction.

I currently run a 1" to 1.2" higher in the rear. My car is a 39/61 weight split.

This may be of interest for some of the modifed Atoms out there making more HP.

thanks

[mynamesnotbob]

Spec as a comparison between cars doesn't really help to be honest. Adding positive rake has three effects as a general rule:

1 - Moving weight - the level of weight you can move is negligible so largely irrelevant but you would be corner weighting your car to get anything meaningful out of this

2 - Changing the centre of pressure and feeding rear diffuser - completely irrelevant if your car is like an Atom as there us the underbody aero on an Atom is simply not designed for this, with little air management feeding a floor (which is not flat) not exciting in a managed way

3 - Moving the roll centre and CofG - General rule if you move this forward you create a more oversteerbiased car, but this statement is true for a closer to 50/50, a very rear biased you would be looking to increase front end. Changing the ride heights will of course effect other factors such as bump steer, overall geometry - so saying lower is better is rarely true

So yes rake does have an effect.

The other thing worth mentioning is where you measure ride height - in a flat bottom car you measure from chassis, you can't do that in an atom as you measure from lower pickup points due to lack of traditional chassis. If you see Atom ride heights it will look as though they run massive negative rake, but they are misleading just due to the nature of the car.

If you have your rake set to 20-30mm positive, then levelling it out would in theory move traction to the rear - but without knowing the car, chassis design, floor setup, car length etc etc its all guess work

If you are lacking rear end traction, optimising rear toe, camber and your shock settings would have far more of an effect. But it depends what aspects of traction you are looking to increase/decrease - corner entry, corner exit, straight line performance or stability