Suspension advice for a bumpy track

[lforter]

So im preparing for a bumpy autocross track (with a LOT of cracks and imperfections) and I need some advice.... For the track I went with Koni Special Active Shocks and stock m performance springs, I believe anything stiffer might make me loss traction and control. Now im wondering about the m3 control arms that I have installed...im planning on keeping the lower control arm for the additional camber, but I have doubts about the tension struts, I feel they add a lot of bump steer which is what I will be dealing constantly, should I go back to the original tension struts? will the pros win over the cons?

any advice? im also leaving whiteline subframe bushings for the track...any advice in bumpy (really bumpy track) is appreciated.

[Brian_]

Don't think M3 tension struts would have any impact on bump steer characteristics as they share the same dimensions as the stock E82 part and just have a firmer rubber bushing.

Aftermarket struts/shocks with stock springs should be a pretty solid starting point.

What alignment settings do you typically run? If you're able/willing to adjust the setup just for autocross a more aggressive alignment can make a massive difference without changing any parts.

[amg6975]

Originally Posted by Brian_

Don't think M3 tension struts would have any impact on bump steer characteristics as they share the same dimensions as the stock E82 part and just have a firmer rubber bushing.

I'm not totally convinced that's true, but also don't know it's false. I would have thought they were longer, or lengthening the control arm would change the caster angle.

fe1rx would probably know of the top of his head, I searched is threads quickly and didn't see that info.

[fe1rx]

Originally Posted by lforter

So im preparing for a bumpy autocross track (with a LOT of cracks and imperfections) and I need some advice.... For the track I went with Koni Special Active Shocks and stock m performance springs, I believe anything stiffer might make me loss traction and control. Now im wondering about the m3 control arms that I have installed...im planning on keeping the lower control arm for the additional camber, but I have doubts about the tension struts, I feel they add a lot of bump steer which is what I will be dealing constantly, should I go back to the original tension struts? will the pros win over the cons?

any advice? im also leaving whiteline subframe bushings for the track...any advice in bumpy (really bumpy track) is appreciated.

The perception of bump steer can come from both a true kinematic bump steer curve in either the front or rear, or from compliance steer effects (primarily due to bushing compliance), or from erratic grip due to under- or over-damping. Stiff springs per se are not particularly problematic and may be better than being continually on your bump stops.

If you don't alter the stock caster angle, in my experience the car has very little kinematic bump steer. In practical terms, I would call it none. The M3 tension struts don't alter the caster so should not be a culprit. They also reduce compliance, which should be a plus too. The increased -ve camber is also good.

As for your basic question - I would definintely keep the M3 control arms installed for your track day. Sounds like for the moment your concern is hypothetical, so no point in making any big decisions/changes until you actually try it out.

[Blau]

Dude, just send it. You're not getting paid to race, just go have a blast.

[lforter]

Alright, course was hard but fun asf. Lots of potholes, bumpy roads, imperfections, water and sand. In some parts a stiffer suspension would have come in handy, but in general a softer suspension was better. the harder the RSBF the better I believe, m3 control arms were neccesary, it was just noisy.