Spare Z4M wheels will eventually become non-existant. In 1990 I bought a 1986 Porsche 944 Turbo that turned out to have a buckled front alloy. It took me over 6 months to locate a replacement alloy. Porsche wanted over £600 (1990 prices, mind, which equates to some £2000 in 2011...). I eventually found a Somerset breaker & got a new wheel for £125.
If you intend to keep your ///M then ,if you have the spare cash, I would suggest that you jump at the chance to buy both a spare front & rear alloy.. :wink: