Originally Posted by Matt W
Could someone please explain bump steer? How does adding or removing shims under the steering block effect the cars handling (steering on entry, exit, on power, etc)?
Bump steer is controlled by the angle of the steering link in relation to the lower wishbone. If they are parallel then you will get minimum bump steer.
Looking at the links from the rear of the car at rideheight...
If they are angled up towards the outside of the car (more than the lower wishbone is) then you will get toe out during bump.
If they are angled down towards the outside of the car (again more than the lower wishbone is) then you will get toe in during bump.
In full size Motorsport most cars run zero bump steer to make the car more predictable over bumps.
In RC touring car racing, because most of the tracks are super flat, we often use the bump steer characteristic as a tuning aid during cornering. In this case the bump steer setting has the greatest effect mid corner when the chassis is a max roll...
With the T3 2012 I believe 1mm spacers are the kit setting. This gives quite a lot of toe out on the outside wheel during cornering, which results in smoother/less mid corner steering. If you run 2-3mm spacers then you get less toe out on the outside wheel during cornering, resulting in more aggressive/more mid corner steering.
Unless the car is too snatchy mid corner, I always run 2 or 3mm spacers as they tend to help maximise cornerspeed.
Hope this helps