torque steer...what causes it? - BMW Forum - BimmerWerkz.com
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#1 (permalink) Old 08-17-2009, 11:34 AM
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torque steer...what causes it?

Hey all,

I have a 1998 bmw e36 328is. I have changed the springs and shocks on the car. They are bilstein hds with bavauto springs. Ever since I completed the mod, my car likes to drift to the right when i really get on the gas. I already did alignment on the car and they said it was okay. What could the problem be?

Thanks,
Ian

///M
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#2 (permalink) Old 08-17-2009, 11:38 AM
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Are you sure the tires are the same right and left? It could be a simple traction difference.

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#3 (permalink) Old 08-17-2009, 11:59 AM
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that could be it......i just got a new tire in the left rear but the right rear is almost new too....installed the tire about 3 months ago. Both tires are relatively the same in wear though. If this is the problem will it go away once the tire is worn in?

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#4 (permalink) Old 08-17-2009, 12:07 PM
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Torque steer is due to the difference in length of the shaft going to either wheel in a front-wheel drive vehicle. The torsional forces take a bit to catch up on the side with the longer shaft when the car is starting to move from a dead stop, thus forcing the car in that direction.

That said, what you are experiencing is NOT torque steer. You drive a RWD vehicle.

Steering rack issues? I'm just thinking out loud at this point.

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#5 (permalink) Old 08-17-2009, 12:13 PM
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okay....so wut is the problem then now that its not torque steer?

///M
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#6 (permalink) Old 08-17-2009, 12:16 PM
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Correct. It is physically impossible to get torque steer on a rear wheel drive vehicle.

What I think the issue with your car is: You have BavAuto springs which are soft. When you get on the gas, the rear squats too much thus making the front suspension decompress which in turn changes it's geometry, and causes it to not go straight.

edit: Just saw the new tire on one side thing. I would check that first, but I wouldn't look past what I posted originally.

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#7 (permalink) Old 08-17-2009, 03:28 PM
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Cool

In theory, and in practice, you are supposed to change tires, at the very least in PAIRS, both front or both rear; or ideally, all four.

The catch is you changed only 1 tire.
My Q is:

are the tires of the same brand/ tread? and tire pressure?... if no, that may be the source of your prob.

Consider also, that you only have 1 driving wheel at the rear at a given time. That is how differentials are designed... unless of course you have "posi-trac"

Last edited by darkhorse737; 08-17-2009 at 03:36 PM.
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#8 (permalink) Old 08-17-2009, 03:54 PM
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Originally Posted by darkhorse737 View Post
In theory, and in practice, you are supposed to change tires, at the very least in PAIRS, both front or both rear; or ideally, all four.

The catch is you changed only 1 tire.
My Q is:

are the tires of the same brand/ tread? and tire pressure?... if no, that may be the source of your prob.

Consider also, that you only have 1 driving wheel at the rear at a given time. That is how differentials are designed... unless of course you have "posi-trac"
Incorrect. Both wheels are spinning at an even rate; only if you lose traction does all the power go to one wheel (one with less traction -- path of least resistance).

If you're going straight and are not breaking traction, both wheels are being spun at the same rate by the differential.

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#9 (permalink) Old 08-17-2009, 04:08 PM
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Thumbs up

Quote:
Originally Posted by Torque View Post
Incorrect. Both wheels are spinning at an even rate; only if you lose traction does all the power go to one wheel (one with less traction -- path of least resistance).

If you're going straight and are not breaking traction, both wheels are being spun at the same rate by the differential.
hmmm... torque, if that is the case, why is it that when you raise 1 rear-wheel off the ground, only that 1 tire will spin and the other will stay stationary. Isn't the what the internal spyder gear is used for?

I could learn something new here :-)
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#10 (permalink) Old 08-17-2009, 04:24 PM
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yea well all the tires are the same brand and are set at the same pressure. Both tires have been changed withing 3 months of eachother and the tread life is relatively the same on both. I might just try getting the car realigned again

///M
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#11 (permalink) Old 08-17-2009, 04:38 PM
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Originally Posted by darkhorse737 View Post
hmmm... torque, if that is the case, why is it that when you raise 1 rear-wheel off the ground, only that 1 tire will spin and the other will stay stationary. Isn't the what the internal spyder gear is used for?

I could learn something new here :-)
It's hard for me to explain since I'm not an engineer (and I already somewhat misworded my last post), so here you go, just read the "loss of traction" section of this wikipedia page:
Differential (mechanical device) - Wikipedia, the free encyclopedia

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#12 (permalink) Old 08-17-2009, 06:07 PM
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alright wells it definitely not the diff...

///M
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#13 (permalink) Old 08-20-2009, 04:22 PM
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Tires are the same size right?
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#14 (permalink) Old 08-20-2009, 04:46 PM
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I would also like to mention that I, in no way, shape or form, caused any steer in the poster's car.


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