: : : The L6 TRX's had an overall diameter of 632mm.
: : : (The M6 actually had an OD of 631mm)

: : : The wheel you are suggesting has an OD of:
: : : 15*25.4 + 2*.6*225 = 651mm

: : : The setup you are being tempted by is about
: : : 20mm larger. That's 3/4 of an inch! I would
: : : not buy it.

: : : The M6 rims were over 16 inches. Your car
: : : had a rim under 16 inches. So it makes sense
: : : to pick a rim size in the middle; i.e., 16".

: : : Again the 225/50 ZR 16 diameter is exactly the
: : : same for all intents and purposes (631.4mm).
: : : I actually run a 245/45 ZR 16 in the rear in the
: : : summer.

: : : Now you have to worry about offsets. Your rim
: : : width was 165mm = 6.5 inches with ~21mm offset.
: : : You don't specify rim width and offset, and
: : : don't bother until you have 16" rim picked out.

:
: : How are you figuring that out. Would a 215/60/15 be a closer match? I'd like to stay with the 15" rim because of the price I can get on them.

: Yes, after thinking about it, a 215/60/15 sounds
: like an excellent choice, especially in the front.
: It would have an overall diameter of:
: 15*25.4 + 2*.6*215 = 639mm (You should see how
: the calculation works. 1" = 25.4mm, which don't
: need for metric TRX wheel diameters. Add two
: sidewalls for top and bottom.)

: The problem with wider tires in front is that
: it often messes up the steering geometry. In
: the rear there is really no downside. I would
: go with 225/55/15 in the rear. That would give
: you slightly larger narrower tires in front.
: And it would give you slightly smaller wider
: tires in the rear. That is how new BMW's are
: configured from the factory, due to the improved
: tire technology.

: Just make sure the offset is very close in front
: (or that you can get there with spacers).

: Let me know how it works out. I'd like to try
: that setup.

As I'm sure you want to know, the OD of the
rears I'm recommending is:
15*25.4 + 2(.55)(225) = 628.5 mm

These dimensions straddle the factory spec,
which, if you recall, is 632mm.