View Single Post
  #22 (permalink)  
Old 01-11-2005, 05:57 PM
Morris Morris is offline
CC Member
Visit my Photo Gallery

 
Join Date: Dec 2003
Location: Gurnee, IL
Cobra Make, Engine: Kirkham #259
Posts: 1,394
Not Ranked     
Default

Many of the older suspensions on these cars have way to much Bump steer in them and I'm not sure that folks know how to get the bump steer out of them

The Kirkhams have done a great job working with the rear suspension to get allot of the bump steer out of the suspension..... they moved the trailing link where it mounts to the lower control arm...... but thats just a start...... it's up to you to actually move the hub thru it's suspension travel and measure what the hub is doing as it travels up into bump and down into droop.....

If the bump steer on a rear wheel goes up to .150" thousandth of an inch Toe-out ..... and you have 1/8" toe-in ......you will transision between toe-out and toe-in as the wheel travels into bump or droop..... this will cause the car to act as if it wants to go in 2 different directions at one time..... very unstable condition.... so in the old days the guy's would just crank in more 1/2" toe-in to compensate for the toe-in and out condition......

This is not the right way to fix the problem.... it is just a bandaid... and will have an unstable condition in the rear of the car.....

Most folks don't know how to adjust bump steer on the rear of a IRS car and especially one that has Anti Squat ...... so crank in the Toe-in.....Wrong....

First you have to relocate the trailing link so it's in the same arc as the lower control arm..... or as close as you can get.....

Then.....important......then you can rotate the upright on the axil to change the bump steer and get the wheel going up into bump and droop with-in the spec's of .015" thousandths per inch of travel....... I think on our rear suspension we got it down to .030" thousandths of an inch in 4.5" of travel...... but this is a very small movement of the upper control arm on the rear.....

This is something that has been around for a long time ....just not many people knew about it.....

Anyway do the same thing on both rear wheels....and get the rear end going the right way when it goes into bump or droop....

After you get your Bump steer worked out and I would invite you to go over to Gasholes and see how we did what we did.... then go back thru the alignment and re-do all of the settings..... and only then will you be OK.....

The best thing is that if you can do the alignment with strings or straight edges or what ever.....you can come back after you drive it and make adjustments .... there is now magic to this alignment stuff ...just get yourself some reference points and then go from there.. and don't be afraid to make changes and see what they do......
__________________
Morris
Reply With Quote