Hi. Can anyone say under which conditions with aftermarket wheels is one most likely to get bump steer ? I understand bump steer to be felt by the steering wheel twisting by itself in your hands as you drive over uneven surfaces. The car feels twitchy and unplanted and wanders on the road. Would wider wheels contribute because they are simply wider -besides tramlining- or does it depend where they are wider. i.e. increasing the track ? What of offset ? What is offset actually ? Do wider aftermarket wheels use the same wheel alignment numbers as the stock wheels ? Thanks Greg
Wider tires in the front will cause more bump steer and wandering on the road surface. If the wheel/tire combo is also heavier, you will feel more bounce from the wheels as well. This, I know from experience. You may get a little more ultimate grip from wider tires but there are tradeoffs. There is so much body roll in stock 308/328 suspensions, you will find there is little benefit in handling anyway. Dave
I may be off base here, but I thought that bump steer usually occurs when a car's ride height has been altered significantly such that the suspension geometry is no longer as designed and travel up and down results in a change in steering input even if the position of the steering wheel does not change. If the wheel outside diameter does not change, then there would be no more or less bump steer than before. That said, there would be more steering feedback for irregularities in the road, but I don't think that is technically bump steer.
Correct - bump steer occurs when the suspension geometry is such that when a front wheel hits a bump, the upward motion of the wheel causes the steering to turn the orientation of the wheel in one direction. Properly designed suspension and steering geometry requires that the steering angle of a wheel does not change noticeably as the wheel moves up and down in normal travel. A poorly designed suspension, or altered factory suspension by lowering, can result in bump steer with normal movement of the wheels over bumps. Changing offset of the wheels can affect bump steer feel if there is a bit of bump steer to start with. Tugging and pulling of the steering wheel as you drive is not bump steer, it's more commonly referred to as tramlining, where the tires have a greater tendency to follow imperfections in the road surface. Changing offset, or changing to lower profile tires or wider tires, will usually increase tramlining.
