Bump steer?
Thread Starter
11 Second Club
Joined: Apr 2002
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From: Waldorf, MD
Bump steer? Is that what it's called when you're going around a corner, hit a bump in the road, and your car wants to go anywhere other than the direction you're steering? Well, how can I get rid of it? Whever I ride with my buddy in his 02 Firehawk the same thing happens. Granted, he's got Koni shocks, but they're even on the softest setting. I also know that our cars don't have IRS, but is there a way to keep the rear tires glued to the road on rougher roads?
TECH Junkie
Joined: Mar 2002
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From: memphis tn
Bumpsteer is caused by camber changes in your suspension as it travels up and down through it's normal range.When a bump or suspension compression it is amplified by the change in camber.Adjustment for bumpsteer in the front suspension is typically made by raising or lowering the steering rack to find the best compromise in camber change.Rear bumpsteer adjustments are more difficult.
While camber changes DO happen while the suspension travels up and down, bumpsteer is the changes in toe.
The tie rod end is at a set level at the rack. as the suspension travels up and down, the poit attached to the wheel travels in an arc, shortening and lengthening the relative distance between the steering knuckle and steering rack.
At factory ride height, the rack and steering knuckle are level. So the arc is symetrical and the changes in toe are symetrical, both above and below the steering knuckle and it's opposite side.
When you change the geometry, like when lowering the car, you change the toe. When aligned to compensate, the symetry is gone. As the car leans over in a turn, one side compresses, but at a reduced distance and the other side droops at an increased distance. So, the compressed side gets a tiny bit of toe change and the droop side gets a whole lot.
This changes the turn angle of the tires assymetrically.
Example, as you turn to the right, the drivers side tire toes in ever so slightly which helps the car turn. The passenger side, tire toes in a great deal more attempting to straighten the car out
BAER makes a bumpesteer kit, which is just a sterring knuckle relocation kit.
Now, having said all that, F-Body's just don't have enough suspension travel for this to be an issue in normal, daily driving.
I suspect your friend hasn't a clue on how to set up his shocks (the reason I don't have adjustable shocks) and this is causing the problem. Especially if he has them set to full soft on bump. If the suspesnion bottoms out while turning and you hit a bump, the spring rate goes infinite and the car will push out.
The tie rod end is at a set level at the rack. as the suspension travels up and down, the poit attached to the wheel travels in an arc, shortening and lengthening the relative distance between the steering knuckle and steering rack.
At factory ride height, the rack and steering knuckle are level. So the arc is symetrical and the changes in toe are symetrical, both above and below the steering knuckle and it's opposite side.
When you change the geometry, like when lowering the car, you change the toe. When aligned to compensate, the symetry is gone. As the car leans over in a turn, one side compresses, but at a reduced distance and the other side droops at an increased distance. So, the compressed side gets a tiny bit of toe change and the droop side gets a whole lot.
This changes the turn angle of the tires assymetrically.
Example, as you turn to the right, the drivers side tire toes in ever so slightly which helps the car turn. The passenger side, tire toes in a great deal more attempting to straighten the car out
BAER makes a bumpesteer kit, which is just a sterring knuckle relocation kit.
Now, having said all that, F-Body's just don't have enough suspension travel for this to be an issue in normal, daily driving.
I suspect your friend hasn't a clue on how to set up his shocks (the reason I don't have adjustable shocks) and this is causing the problem. Especially if he has them set to full soft on bump. If the suspesnion bottoms out while turning and you hit a bump, the spring rate goes infinite and the car will push out.
Thread Starter
11 Second Club
Joined: Apr 2002
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From: Waldorf, MD
Originally Posted by mitchntx
I suspect your friend hasn't a clue on how to set up his shocks (the reason I don't have adjustable shocks) and this is causing the problem. Especially if he has them set to full soft on bump. If the suspesnion bottoms out while turning and you hit a bump, the spring rate goes infinite and the car will push out.
Just so I don't make the same mistake, what can I do to my car to make the front/rear more glued to the road around turns? The roads here in D.C. suck, and I hate it when I'm traveling a curve at 75, hit bump, and my car wants to jump all over the place.
On The Tree
Joined: Jun 2003
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I've found the key to keeping the rear-end planted around curves, etc. is making it soft. My rear end will skip around now with stock rear springs and Bilstein HDs (3rd and 4th Gen). However, I tried a set of Bilstein 3rd Gen Sports somebody let me borrow, and they were awesome on the bump (the bump and rebound rates are about 50% of what the HD rates are). The lack of rebound sucked, but with the reduced bump rate, the rear end stayed planted through areas where I had been having problems with it skipping with the HDs.
Also, springs will cause the rear end to skip around. The 1LE rears are really too stiff, IMO. I had them on with a 21mm rear bar, and the rear end would jump around all over the place every time I hit big dips and bumps on the freeway. They were somewhat tolerable with a 15mm rear bar, but the stock rears were best. Hope that helps.
Also, springs will cause the rear end to skip around. The 1LE rears are really too stiff, IMO. I had them on with a 21mm rear bar, and the rear end would jump around all over the place every time I hit big dips and bumps on the freeway. They were somewhat tolerable with a 15mm rear bar, but the stock rears were best. Hope that helps.
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