I have a Y2K M Roadster. Currently have original Dunlops on it. When the time comes to replace them I think I'll want to go with Michelin Pilot Sports. There has been talk on the Z3 MB of increasing tire size recently when replacing tires. If I'm not mistaken, some have said that they have done so with the Pilot Sports. When looking at the available sizes in the Tirerack.com site for the pilots, the only sizes that are ZR rated are the OEM sizes (225/45 ZR 17 and 245/40 ZR 17). To go up a size up in this particular tire, are they going to a YR rated tire? I'm new to all this, so maybe there isn't much difference beteween a ZR rated tire and a YR rated tire.