Quote Originally Posted by TODA AU View Post
Bump steer is generally a geometry problem.
When the car is lowered beyond the limits of the standard parts, the geometry of the steering arms is compromised.
This can be cured with a variety of products.

Adrian
Agreed, up to a point. If you've made substantial changes to ride height and / or caster angles then you may well end up with geometric bump steer (i.e. true bump steer, not a torque steer affect), and you may well be able to address it by arbitrarily throwing appropriate parts at the problem. However, the only way to know if you've actually cured it (other than the problem no longer being apparent when you drive the car) is to measure the bump steer.

This is done by maiking a tool that consists of two flat pieces of plywood hinged together so that they can open / close like a book. On one piece of ply you fit two pointers (can be anything, a couple of screws screwed though the ply so they protrude out the back will do fine) spaced apart so they match the rim diameter and high enough so they will be at hub centre height when you place the pointers against the rim.

But I'm getting ahead of my description. Place one 'page' of the bump steer tool / gauge on the ground near the wheel with the other page up against the wheel, and place some bricks on the 'page' that is on the ground to hold it in position while the bump steer test is performed. The pointers on the vertical 'page' are placed against the rim so that both are touching the rim. Now the car must be jacked up and down while you observe if one of the pointers moves away from the wheel rim with ride height changes, if so then this indicates a toe change with ride height change and thus bump steer.

In order to do this test you need to remove both coil springs on the front axle line in order to allow ride height change as you jack the car up and down. This is fairly easy with 'coil-overs', more of a pain with struts.