GTD Front A-Arms

[Malcolm]

Howard,

Have you raised your steering rack height? 7/16 inch reduces the bump steer quite nicely. I have done this and shimmed the front suspension brackets as required to get camber and don't suffer bump steer.

 

[Howard Jones]

Thanks Malcolm.

I already knew that but I haven't done it yet. That is next on my list however. It's good to have confirmation on this from someone who has done it.
Thanks again.

Overall ol Betty is starting to get with the program. The ol broad needed a little "work" but now she is really comming around in the handling department. Before too long it's gonna be.......dare I say...... more power time.

Anyway we have a date at the track next month and I can work on setup some more. I'll report back after that with a update on suspension settings.

Howard

 

[Mike Pass]

The 7/16" shim works well as Malcolm says. If you have changed the length of the arms it would be well worth checking for bump steer. If you can borrow a bump steer gauge that would be excellent but you can make a gauge fairly easily. Have a look at the stuff from Demon Tweeks or GPR and make one from mdf. The simplest is by attaching/bolting a flat plate to the hub. lean a sheet of mdf which is accurately pivotted (no play in the pivots) at the floor. Attach two pointers (about 3" long with slightly rounded ends so they will slide on the hub plate) at the top edge of the mdf sheet so they touch the plate (at about the hub centre height) on the hub at two points. As the bump steer moves the hub one of the pointers will move away from the hub plate. Swing the suspension without the spring/damper unit through the main range of angles used in normal driving by moving up and down with a jack in small equal steps (1cm). At each step check the toe out/in by measuring the gap as it opens or closes. This can be done with a dial gauge, a vernier caliper or feeler gauges. Juggle the rack position until the bump steer is the best or should I say least bad! A graph should show what is going on in terms of toe out/in. There are many ways of ensuring no bump steer. The simplest is to ensure that the inner track rod end and the inner suspension pick up points are all in the same plane. The other way is by trial and error - moving the rack up and down (and even back and forward) till it's OK. Usually the shimming up and down of the rack gets it to the point that it works OK.
Cheers
Mike