Reply to "Bump Steer Spacers"

One of the modifications that Shelby did on the 65 Mustang to make it a GT350 was to lower the location of the upper a-arms.

The ideal lowering on a 65-70 Mustang is 2".

The problem is that the lower ball joint would not tolerate that without being shimmed with a wedge shaped spacer.

Apparently neither Ford or Shelby wanted to pay for that.

The compromise was to lower it 1".


I have a '68. I went the radical departure of 2" AND used an angle ball joint spacer.

Now this definitely added handling capabilities in cornering since it put the tread more parallel to the ground as the car rolled in a corner. Good you say?

Now to the point, aka, the issue. By doing this a large amount of bumpsteer was installed into the car.

So much in fact that the car would change lanes, not an entire lane, but about a 1/2 a lane just cruising down the road and either tire hitting an "imperfection" in the pavement that the other hadn't.

If you ask me for what the definition of bump steer is, that's mine.

The car has since had bumpsteer modification done to it and along with radial tires, tracks very straight under every condition I could give it.


The Pantera, even the early one without the factory shim, is a pussycat. You might or you might not think that you felt something in the steering.

With the factory shim, I won't even spill my cup of cappuccino.


I don't disagree with Bosswrench at all with his statement BUT each corner must be able to travel close to it's travel limits while the other doesn't waiver at all.

That is VERY difficult to do, if not impossible since the suspension travels in arcs, not straight lines.


One way of reducing bump steer effect at speed is to dial in as much positive caster as you can.

This really would be very important with a wide body. Much more so than the original slab side design.

5 degrees of positive caster is going to deaden much of a bump steer effect right there without having to go to much further.

The problem with that is you will be at the point of needing power steering assist.

Solutions in one area rarely are done without causing drawbacks somewhere else.
Compromise is the term that comes to mind?

Some drivers don't even know what bump-steer is or that their car has it? They just accepted it, "whatever that was", as a fact of everyday life?