I have just had the SSS getting the corner weights checked and the question of bump steer has been raised.( especially given the apparent torture that the right front has taken in one meeting )
Has anyone any knowledge of just how bad the 1200's generally are and what mods are done to fix it?
Cheers
Dave

1200s are not known for problems with bump steer.

You know you have bump steer if when going down the road in a straight line, the car turns slightly (steers) whenever it goes over a bump. 1200s normally have a bit of "wandering" because of too little caster but this occurs even without bumps (the solution for this is to set the alignment to 2 degrees caster).

If you do find bump steer, it's usually because of extreme lowering -- more than 2". In which RCA spacers can help. Less common cause is shortened or lengthened LCAs or tie rods.

Thanks DD. This question is really directed at the guys who are competitively racing the 1200's.
Dave

what dd said is spot on.

what is the "apparent torture" you are referring to? and what is your current suspension setup? and what type of events are you planning to do?

you asked a very open question without giving much detail, so i don't think it can be answered any better than DD did.

a good wheel aligner can measure bump steer. It's a simple case of removing the spring, re-assembling and having it on the aligner jacked up to the normal static ride height, then measure the change in toe for about 3" of compression from static height. Or you can do the same at home with a string line setup - just make sure the other side isn't moving as well - will bugger your results up.

bump steer can be corrected with custom outer tie rod ends, to alter the angle of the steering link. Or by heating and bending the steering arm.

bump steer cannot be responsible for excessive outside wear though. It will only be in the magnitude of a couple of mm unless something is very, very, wrong. And the corners would have to be very bumpy for it to have any effect anyway. In normal bump travel from body roll, there is no real effect to the outside tyre, just a fraction of a degree more or less wheel input required. bump steer is very unlikely to be the culprit of tyre wear.

Setup factors that increase front tyre wear are excessive static toe, high roll centre, insufficient camber, too little roll resistance (spring/bar/and shock to a lesser extent)

Do you get excessive graining or any blistering on the tread?
http://insideracingtechnology.com/tirebkexerpt3.htm

Hi Harry,
Thanks for the info.
The guy that I used for the corner weighting just asked the question so it seemed the best way to get an accurate answer was to ask on here.
I have never really experienced bump steer on the track but he certainly was puzzled when he looked at the state of the Dunlop Direzzas.
No sign of the graining or blistering but heat cracks all through the inside of the tread and sidewall ( even on the l/h side ) and the outer third of the tyre tread almost being 'rolled' off.
Anyway I've upped the spring rate now to 275lb and also have a 21mm adjustable front bar. Wheel alignment has been set to 4 degrees - camber, 4 + castor and 2.7mm toe out and I'll firm the Konis right up.
Also tightened up the rear bar although I suspect too much as it is showing plenty of oversteer tendancies driving around roundabouts.
My only other option over here in tyres is a Kumho V70A so I'll grab a set of them next week.
The other thing that did show up with the corner weighting is that there is a 40kg variation on the r/f with me sitting in it and more in the l/r so unfortunately the battery is going to have to come out of the original factory position and go in the boot on the l/h side. I guess at the likes of Levels with all its l/h corners that will not be helping at all. I have resisted doing this to date as I'm trying to keep the car looking semi original...
Cheers
Dave

Agree with Harry,
Also RCAs should not impact bump steer, as they do not change the steering geometry. As others have written bump steer is caused then the relative arcs of the LCA and Steering system are miss aligned. During suspension travel this caused the wheel to be turned in/out over the range of travel (or bump). The problems with RCAs on the 1200 is they usually are placed above the steering arm (Betwen the steering arm and the strut) thus they do not effect the relative arcs of motion. If the spacer was between the steering arm and LCA it would have an impact.

I guess it is possible that lowering or raising the car may move the static position away from a bump steer "sweet spot", (i.e a spot where the two arcs are closely aligned and as such bump steer is minimal), which may be one reason to add an RCA as a solution. But this is generally not the way to address bump steer issues.