[cochapman]

Over the weekend, I changed the springs on my Mk2 214 for the lower, stiffer ones I got a few months ago (GMAX IIRC) and also to change the steering rack to a PAS system from the OEM manual! A quick test drive showed the tracking was massively out…not entirely surprising, so it got a full tracking check yesterday.

Driving in to work this AM, I noticed the car suffers quite badly from bump steer. Each time the car goes over a hump or bump and goes "light" (i.e. very slight negative G), it pulls to the right.

As far as I can tell, the rack is OK, because on the flat even slight movements give corresponding movement in the front wheels. The springs seem good, with a real "go kart" feel to the car now...it is just this annoying bump steer :-( The car has gone from one I was happy to drive flat out, to driving at 50-60 because of being worried about suddenly lurching across the road!!!

Any ideas…please!!!!!

 

[cochapman]

I'd considered this, but the suspension and steering was perfect imediately prior to fitting the springs and the power steering rack.

One thing that a mate has suggested is to do with the rack fitting. As the power rack is bigger diameter than the manual rack, and the subframe rack cutout is sized to fit, the power rack sits about 5mm lower on the passenger side than the manual. Initally, I didn't think this would cause a problem, but I am starting to think that even this slight "misalignment" might be sufficent to cause a difference in the steering geometery from one side to the other.

I came home down a road with sweeping bumps and it was very noticible: in the bottom of the bumps, as the suspension compressed, the car would steer left; on the top of the humps, as the suspenion unloaded, the car would steer right.

I'm going to look at removing the rubber bush on the passenger side and see if that extra couple of mm improves matters. If it does, I'll have to look at changing the subframe or fabricating a slightly larger apperture.

 

[cochapman]

The reason it drives like that is cos your running lowered uprated springs with standard dampers. Surprises me this, most of the time if you put just lowering spring on a standard car you can actually make it handle worse than before. Put some uprated shocks on.

I'd considered this as well, but why would this lead to bump steer? I can understand the car being "under-damped" in relation to the springs and giving some odd effects, but surely to give the steering effect, there must be some kind of mismatch from left to right?

As it is, I've just removed the sub-frame from the car fitted with PAS...so the next question is...once the rack is out, can I change the subframe with the engine in place?

My son has just seen the smilies and he wants me to put this one: :guns4: