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Q's on bump steer with turn in spacers (long)

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Q's on bump steer with turn in spacers (long)

Old 07-26-03, 08:02 AM
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Question Q's on bump steer with turn in spacers (long)

I am getting conflicting info from two very reputable 1st gen race shops. One says use turn in spacers to restore the roll height, and to get ackerman. The other says using turn in spacers will require you to "bump steer the car - which means heating and bending things" and increased ackerman isn't important on this car". Both are referring to full race setups.

As I understand it, bump steer is caused when the tie rods are no longer parallel to the ground after lowering. If this is true, it seems to me that turn in spacers would help this problem if you lower the car.

I'm setting up my 1st gen for street/track with a heavy emphasis on track, and I plan to install the following:

GC coilovers with 350# springs in front
camber plates
1-1/4" turn in spacers
150# rear springs with stock bushings (may switch back to 110#'s depending on results).

My questions relate to the need/effect of the turn in spacers. I have Susko's book, but unfortunately, I am not installing the full system (yet). I won't be lowering the front to his recommended 5" ride height because I am not addressing the rear. Right now the car has about 6-3/4" at the front bottom of the fender and about 7" at the rear.

So here are my questions:
1. Should I even use the spacers if I only plan to lower the car slightly from where it is now?
2. Any recommends (based on experience) on how much to lower the front given the fact that I won't be lowering the rear much if any?
3. Does any body using turn in spacers have bump steer problems? What ride height are you using?

Thanks,
NGueldner
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Old 07-26-03, 10:05 AM
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Bump steer is caused by a change in relation ship between the inner and outer pivot points of your tie rods. The heating / bending is used to moved the steering arm down when you lower dramatically.

The "turn in spacer" is used on the bottom of the strut. On a stock first gen your lower control arm has a ball joint. Connected to the ball joint is your steering arm. Bolts hold the bottom of the strut to the steering arm.

When you lower the car the bottom of the strut moves up inside the wheel well. The steering arm goes with it - as well as the outside of the control arm.

The turn in spacer will lower your steering arm back down - taking the outer tie rod pivot with it. It also puts the control arm back down to where it needs to be - This will bring your lower control arm geometry back to stock. You want this so your camber curve is retained.


If you do end up lowering more than an inch. You will need turn in spacers. You should also look into shortening the strut tube and run a shorter insert for anything over an inch.


-billy
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