Originally Posted by TomTarzian
The space saver wheel from the X6 (part number 36-11-6-768-861) mounted with a 125/70-18 space saver tire will fit on both the front and rear of the E9x M3 without a spacer. The only problem is that the center bore of the X6 wheel is a bit larger than the E9x M3's hub so you have to be very careful to center the wheel on the hub when tightening the lugs. I'd like to find an adapter to properly center the wheel on the hub but without an adapter this setp works fine at least at moderate speeds and for relatively short distances.
Thanks for that. Is that the same as use for the X3 (my post #11)? That calcs out to an inch or more smaller OD than stock. Wonder if there is a 125/80-18 available?
Edit: I just found that the Cadillac CTS uses a 135/80-18, which, at ~26.5", would be a little larger than the stock 26.3" rear.
I'm sure you could have an adapter machined pretty easily, but would be nice to find a pre-made one. Do you know the centerbore diameters? X5 is 74.1, so I assume X6 is the same? (M3 CB = 72.56).
Edit: I found the proper hubcentric plastic rings here (74.1/72.56): http://www.1010tires.com/hubrings.as...FU0wpAodcQqcmw $21/set of 4.