Suspension Geometry question, What cause a car to wander under heavy braking? |
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Suspension Geometry question, What cause a car to wander under heavy braking? |
nine14cats |
Aug 2 2006, 01:55 AM
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Bill Pickering -- 914-6 GT aka....Leeloo Group: Members Posts: 2,618 Joined: 10-February 03 From: Campbell, CA Member No.: 287 Region Association: None |
I have a question for the suspension gurus out there. I am experiencing some wandering in my car during heavy braking out of high speed sections into sharp corners. Visualize turn 7 at Sears, turn 14 (CCW) at Thunderhill, turn 2 at Laguna Seca. When I get on the brakes hard, the car wanders and "twitches" a bit. The car doesn't jump and it's not out of control, but it keeps you busy, busier than I'd like. I'd like to refine the car to not exhibit this trait.
My thought (and others) is that under heavy braking the front squats and the toe out becomes excessive, allowing the car to follow the undulations in the track pavement. What are possible causes of this as the front suspension goes through it's travel? One possibility could be linked to my front strut steering arms on my car. I have coil over RSR style struts with "custom" bends in the arms. The shop that built the car put a custom bend in the arms when they fabricated the raised spindle. Can a non uniform bend to the arms contribute to excessive toe out under hard braking? Thanks, Bill P. |
groot |
Aug 2 2006, 06:36 AM
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#2
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Dis member Group: Members Posts: 896 Joined: 17-December 03 From: Michigan Member No.: 1,444 |
Assuming you don't have any significant toe compliances (I'll get back to that later)... it's certainly possible that your front toe curves are causing this issue. It's pretty easy to verify, too. Run bump steer on both front wheels at the same time and see what your total toe is doing while the wheels are moving up. It could just as easily be the rear toe change, too. So, it's not a bad idea to check the bump steer at the rear, too.... but in rebound....since the rear should be raising up under braking.
My car had wander issues under braking. But, it was due to toe compliances that I was not aware of at the time...... the right outer rear suspension console was seperating itself from the chassis..... causing toe out under braking. Check for these things first. |
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