mrvette

Jim, I have inquired as to just how bad you feel that bump steer will be with the unequal length tie rods.....19.5 vs 21.5 inches....do you feel it will be a problem??? if so, I just may change either the mounting or modify that adaptor block again.....
I was sorta hoping that with all that long radius it would hardly be noticed...

GENE

norvalwilhelm

Isn't a big factor in bump steer the difference in height between the inner and outer tie rod ends. A corvette manual I have gives this allowable difference as about 1 inch. They call it a Z spec or something. They talk about bulldozing the springs until this height is right. A local stock car driver heats and bends the spindle to match the inner tie rod.
Bump steer also has alot to do with the arc of the lower A arm and the arc of the tie rods passing through the same center.
I don't know what I am talking about but from experience I have run into alot of problems with bump steer. Like 2 inch toe in change.

Jim Shea

First of all, you want to have your suspension/steering pivot geometry designed such that you minimize bump steer. (Bump Steer the rotation of the road wheel about the kingpin axis as a result of suspension jounce and rebound motion. You want to keep your bump steer at a minimum so that when you do hit a bump, there is a minimal affect on the road wheels.

When you have both tie rods of equal length and they pivot at mirror images of each other, the thing that happens when you go over a bump with both tires is that the right and left tires both move in or out together due to bump steer. (Sort of cancelling each other out.)

Now when only one tire hits a bump, obviously only the one side experiences bump steer. But if bump steer is minimized in the first place, you may not even notice.

This is what you are hoping for with your unequal length tie rods. It all depends on how much bump steer that you have in the first place (it's going to be different side to side.) If you were to remove the front springs from your car, you would be able to move your suspension through its entire travel. You could then quantify how much the road wheels move as a result of suspension travel. The only thing is that I don't have information as to what would be "good" or "bad".

It is my understanding that the production C3 suspension has quite a bit of bump steer. That amount would at least be a bench mark.

mrvette

Yes, I think youare correct there, but I have the ends somewhat higher with the suspension relaxed, as the engine is not in yet....so it's a swag for me at this point....I think it will be ok though...on that score...
thing is, the swing radius has a 2" differance in length because pivot to pivot the arms are not equal length...so how bad to figger that will cause bump steer...
is it going to be REALLY bad, or barely noticeable.????
driver's side is 19/5 inches and pass side is 21/5 inches...so will that 10% be noticeable at say 140 mph??? over some rises and bumps??? on a score from one to ten, ten being worst case....where you all put my bump steer problem at???

GENE

Jim Shea

This is just my guess. Since you are using relatively long tie rods, I would think that you can get away with unequal lengths. However, this assumes that your basic geometry (i.e. pivot locations relative to suspension pivots) is acceptable.

Since the Steeroid system seems to be functioning adequately, I would guess that yours should at least be in the ballpark.

mrvette

Thanks for your time, Jim.....I guess it will be next year before I find out...
lotsa things to do before that....

GENE