ianfergus0n

As the title what is the bumpsteer mod?

frisby

For a fixed position of the steering wheel, the direction the front wheels point will vary depending on the compression of the suspension. That is classed as bump steer.

The bumpsteer mod eliminates this so the front wheels point in the same direction under varying compressions of the suspension for a fixed position of the steering wheel. This compression can be in the form of braking or cornering, and so the mod provides greater confidence under both circumstances.

stu

Dave T-S

Not exactly true. You cannot eliminate bumpsteer, only try and reduce it, or at least in certain situations. The only way you will totally eliminate it is to set the steering arms parallel to the rack/ground, and have zero suspension travel

However you mount the rack, you will always have a certain amount of bump steer either under suspension lift (acceleration), dive (braking) or cornering.

And the angle at which the steering is turned and the effect of bumpsteer will also be affected by the amount of Ackerman built in.

It isn't always a bad thing anyway - on cars with static steering rack arm droop, braking will give toe in, which provides stability under braking

TelBoy

Or

Try "Search"

If you started reading every thread there's ever been on bumpsteer, you'd probably still be going by bedtime.

If your real question is "Is it worth it?", then that's simple.

"Yes".

Leslie

With the scooby standard suspension setup, if you have the steering pointing dead ahead and compress the suspension, the front wheels will toe out from the original setting. This is bump steer. The effect is to make the outside wheel on a corner(which is doing most of the work) toe out as the body rolls and the suspension compresses under load. This will induce understeer which is a stabilising effect but does not aid cornering ability.
Some cars have more bump steer than others. If the effect was opposite, ie the bump steer caused toe-in, the car would feel pretty unstable as you steered into a corner.

If the steering rack's vertical position is lowered in the case of the Scooby by the correct amount for the individual car, the bump steer will be reduced and the car will handle much better. In the case of my car, Powerstation demonstrated to me that the bumpsteer was reduced from 40 minutes, which is significant, to 1 minute on full suspension movement! With the rest of the suspension alignment the handling of my car was improved out of all recognition and the front tyres wear flat now instead of the inner shoulders wearing out.

Hope this is helpful to you.

Les


[Edited by Leslie - 2/19/2003 12:15:23 PM]

[Edited by Leslie - 2/19/2003 12:20:54 PM]