bump steer at US height?

[BrokeMyCar]

Hi folks,

I've been noticiing a bit of bump-steer on my 911SC (190k miles). I measured my ride heights, and clearly they've drifted. Just to confirm, in the absence of a bump-steer kit, I should set it to the US spec heights to minimize bump-steer, right? I have an appt for an alignment tomorrow.

Thanks,

Babak

PS the reason I initially looked into it was that my rear tires wore out their inside tread awfully quickly, and the tire place suggested that I lower the rear by 1" or so to minimize it happening with the new tires.

[Bill Verburg]

The 911 steering wheel will always feel alive in your hands, moving a little l/r as you drive along. This writhing feel is not to be confused w/ bump steer.

As the outer end of the steering tie rod moves above or below horizontal it will pull the wheel left or right.

If it starts above or below horizontal it makes that movement excessive, that is bump steer.

So as long as the tie rod is horizontal when staticly loaded you will have the minimum possible amount of bump steer.

The easist time to evaluate this is when the car is on an alignment rack.

As to the rear, if the tires are worn on the inner edges that is generally a sign of lots of negative camber, feathering indicates a lot of toe. Lowering will make that worse unless the camber is also changed via the adjusters.

I like them at the low end of euro ride height, w/ a slight forward rake.