I mentioned this in another thread, but I've been pondering the issue without getting much enlightenment, and I'm hoping someone can tell me what is going on...

The issue is that on my `05 S with factory LSD, there is a repeatable behavior that is almost deadly, and I cannot figure out why it happens.

When passing on a country 2-lane road with a good crown on the pavement, as the car passes over the center line, the LSD suddenly engages and tries to wrench the wheel out of my hands, pulling me back toward the car I'm passing.

It only lasts a second, but it pulls the wheel hard enough to cause an accident if you don't have a firm hand on the wheel, and then it's over, except for cleaning up the seat...

So I have two theories as to why this might happen:

- Crossing over the center of the road to the opposite slope on the other side changes the toe of the drivers-side wheel, and this somehow triggers the LSD. You are accelerating to pass, and the toe could change as you pass center, or the wheel speed could change momentarily,
or,
- Crossing over the peak at the center un-weights the drivers-side wheel enough that it slips under acceleration, thus triggering the LSD.

Neither of these theories makes a lot of sense to me, and I'd welcome any other ideas about what is going on.

The behavior is not specific to my car. I've confirmed with a trusted MINI Service Adviser that the issue happens with factory LSD, including on her car.

The one other observation about this is that adding the Cabrio diagonal braces essentially cured this behavior. It just no longer happens oin my car since installing these braces.

This part, in particular, puzzles me - it seems to me that if the braces make the front sub-frame stiffer and the chassis less compliant, under the theories above, it seems as if it should make the problem worse instead of better.

Any thoughts on this appreciated.

 

I posted a thread a while ago titled "handling problem". Now at the time i couldn't for the life of me figure out what could be causing it. I and a lot of other people, including my suspension engineer who i only met a year ago, and we inspected the suspension meticulously, trying different alignments, and couldn't fix the problem). He recently came up with the idea that the differential (i have an 05 with the LSD) could be causing this bad behaviour.

However my problem doesn't seem to be similar to yours, but i'm trying to go through all the threads related to possible LSD issues. BMW refuse to believe that the problem could be differential related.

I will report once i change the diff (hopefully to a quaife).

 

Could it be from crossing ruts in the road at an angle that causes you to unintentionally swerve? What wheels are you running(offset far from stock?)? My summer O.Z. wheels don't like ruts.

Jeremy

 

This sounds just like the R56 issue, where it turns out not the factory LSD but the front control arm bushings.

 

I'm having the front control arm bushings done in a couple of days, and I'd agree with the possibility that it could be a cause, but it seems to have been 90% fixed by the diagonal braces.

Maybe the bushings will get that last 10% of the weirdness.

 

It sounds like torque steer to me, you're stomping the throttle as you're moving over to pass? And downshifting to 4th, maybe 3rd? Try changing lanes first and then accelerating and see if it still does this. If the road has deep ruts in it, that could do it too, I feel it sometimes in mine.
Stiffer chassis lets the suspension do its job better, your suspension should move, not the body.

 

As you said, the key here is that there is "a good crown on the pavement." I never experience this problem on my '05 with LSD, but I don't drive many roads with a significant crown. FWIW, your theories don't seem unreasonable to me, although wouldn't there be a change in camber? The car is suddenly using a lot more of the inside edge of the tires and it has to adjust. And let's face it, our factory LSD's aren't the best.