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Discussion Starter · #1 · (Edited)
This is a question that I should know the answer to by now.

It just occured to me; Stock.. isn't the M Coupe (or Roadster) lower than the Z3 Coupe (or Roadster)? Lower, as in, less space between the top of the tire and the lip edge of the wheel arch. Or are they the same?

Does the M Coupe use the exact same trailing arm geometry as the Z3 Coupe? I know the two cars have different stifnesses of springs at all four corners, and I know there is a castor difference for the front steering pins between the two. I'm referring to the rear end of the car and the angle of the trailing arms at their subframe pivot point.

The reason I'm asking is this: Correct me if I'm wrong, but its the subtle little angle that the trailing arm's pivot points are designed at, combined with the way the axle moves up and down --> that produces the increase in negative camber for the tires as the rear suspension travels upward. Right? So what I'm wondering is, if the M Coupe is already a little lower than the Z3 Coupe, AND, the two cars have identical geometry (trailing arm angles), then a Z3C owner could lower their car at least to the point that the MC is lowered to.. stock... and not drastically change tire wear conditions at all.

I get pretty good tire wear now. A little excessive on the inside, but not wildly so. It was just occuring to me that it doesn't seem like the MC wears tires any faster on the inside. At least, MC guys don't seem to mention it any more than Z3C guys.

Of course, none of that comparison logic works, if the MC isn't any lower in the first place. Or, if the two cars have different trailing arm angles.

Thinking out loud about tire wear issues with lowering, plus.. I'm just looking to learn more about our car's suspension geometry.

Thanks boys.
 

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The 3.0 has more negative camber in the rear than the M if it has the sport package.

M rear camber is -1.75 +/- .5. Rear toe is .5 +/- .22.
3.0 rear camber -2.5 +/- .5. Rear toe is .63 +/- .22.

Ride height is same in TIS for M coupe and 3.0 coupe with same wheel diameter (588mm with 17" wheels). Trailing arm part numbers are different, which is where I suspect the increased negative camber comes from in the 3.0.

Roadster is slightly different; the 3.0 roadster shows a ride height of 593mm in the rear in the TIS. M roadster shows 588mm. This varies though; mine was more than this, presumably due to the springs that get used when you order the hardtop from the factory. There was a short discussion of this earlier this week.
 

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I've asked this question as well... the experts replied saying the subframe and trailing arms are both different between the Z3s and M-Coupes. I knew the trailing arms were -- that's pretty obvious given that the wheel offsets are different between the cars.

Regarding the subframe, I don't know if there's any geometry different there, or if the M version is a reinforced version.
 
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