Jackei,

You bring up some really good questions.

I simplified a little bit earlier when explaining about the effect of wheel-knuckle force on the steering wheel. The simple explanation is that we get "complete isolation". The truth is that we get "near complete isolation". The long explanation is that the recirculating ballscrew racks have a holding/resisting force of F=2*pi*(Frictional Torque)*(Thread Pitch)+Force(steering damper). This means that the isolating force I spoke about is actually a linear function of frictional torque and thread pitch. Considering the relatively high steering gear reduction even taking into account the relatively low frictional torque of the ball bearings - the holding force (and therefore steering isolation) is designed to provide considerable isolation.

Now, I have not analyzed the Crossfire's suspension in any detail. It is possible that the Crossfire's suspension has some measure of bump steer - the fact that you mention this steering wheel wiggling occuring on uneven roads tells me this is a possibility. Bump Steer is a situation where a fixed tie rod length and pivot forces the wheel knuckle to turn when the suspension is compressed or extended.

I'm just guessing, but if you are noticing the steering wheel move and the front wheel suspension is at different heights on the left and right side, then you are experiencing bump steer.

 

From Wikipedia, the free encyclopedia



A contact patch is the term applied to the portion of a vehicle's tire that is in actual contact with the road surface. The shape of a tire's contact patch can have a great effect on the handling of the vehicle to which it is fitted. Specifically, for the type of wide tire fitted to many modern performance cars, a contact patch that is wider than it is long will increase the tendency for the vehicle to 'tramline' or follow uneven road contours.

 

thanks guys for all your technical explainations. now I feel more comfortable since it looks like this is due to the design of the car, and I'm not the only one experiencing this issue.

 

What your feeling in the steering is normal for the type of car your driving.

 

I also want to make it clear that not all cars have bump steer. Some cars are able to engineer out bump steer. This is considered a good thing. This may explain why you experience this more in one car than another.