Bump Steer

[chris_seven]

I have looked at quite a few of the threads covering this subject and the debates between rack spacers and bump steer kits whic all seem to favour the bump steer kit.

I imagine that an RSR strut which is lowered by 18mm has a standard steering arm and that this change of position generates bump steer.

Does anyone have any information regarding the change of toe from full bump to full droop with this set up?

I used to rally a Ford Escort Mk 2 some years ago and fitted an engine crossmember with lowered rack mounts and generated a huge amount of bump steer - several millimetres of change in toe.

The car had Bilstein struts and we solved the problem by bending the steering arms (and re-heat treating) which transformed the car.

Has anyone tried this with a 911? and if so could some Ackermann be intorduced at the same time?

[DW SD]

Bending the steering arms is a common solution. It will change the steering ratio, which can be a blessing or curse, depending upon your perspective.

I'd like to do use the trigonometry to calculate the change in toe, but don't have the time. I know it easy to calculate. The good news is the changes can be made quite easily after the RSR (raised) struts are installed.

There is no shortage of reading on this topic. Did you try using different key words?

Doug

[burgermeister]

What do you mean by "lowered 18mm" strut? Do you mean spindles are raised by 18mm, thus giving original 911 geometry for an 18mm lower car?

This may, or may not, be directionally useful for what you are looking for.

Ride Steer / Bump Steer

Some of it has been refined a bit more these days - if you're interested, I can post the newer plots, but they're qualitatively similar.

[chris_seven]

Originally Posted by burgermeister

What do you mean by "lowered 18mm" strut? Do you mean spindles are raised by 18mm, thus giving original 911 geometry for an 18mm lower car?

Yes, obvious really if you just spend a few minutes thinking. Thanks.

I will still measure the bump steer to see what measurement we have with a standard car and lowered by 18mm.

[burgermeister]

Originally Posted by chris_seven

Yes, obvious really if you just spend a few minutes thinking. Thanks.

I avoid thinking - it makes my head hurt.

Clear communication is so overrated - interpretation is the way to efficiency!

Thanks for the lesson.

[calling911]

Originally Posted by burgermeister

I avoid thinking - it makes my head hurt.

Clear communication is so overrated - interpretation is the way to efficiency!

Thanks for the lesson.

Yes, takes less oxygen.