I am running non-runflats and wanted a cheap spare tire and wheel. People have mentioned the leatherz.com doughnut but with the fitment kit needed for the e90's its $305 and the shipping is $25 for a total of $330.
I spoke to tire rack and did the circumfrence calcs and found that a 225/45/17 tire will fit with a 17*7.5 wheel. It is a pretty perfect circumference match for the stock sports package setup on the 335 and is also within tolerance (1% circum. diff on front, 2% on back) to use with 19's (265*30*19 rear, 235/35/19 front).
At tirerack a 225/45/17 fusion hri (a Bridgestone brand) is $68 and a sports edition A7 wheel is $104. With mounting, balancing, and shipping it will make a good spare for under $190. Why the fusion tire? It's asymmetrical (not directional) so you can use it on both sides of the car.
A tire cover is probably around $10 at the nearest autoparts store and the extended jack kit is about $115 + shipping from tischerbmw.com. Part number 71106773536 (The jack kit is really nice).
I understand people who just use a mobility kit, but if I'm on a 200 mile drive to the beach through prime corn and chicken farms in Delaware, I don't want to be out there for hours waiting if it's a major hole in the tire, when I could throw on a spare and keep moving.
Tischer site for entering jack kit part number: http://www.trademotion.com/partlocat...&siteid=214336
A good tire circumference calculator: http://www.miata.net/garage/tirecalc.html
Item Description Availability Qty. Price Each Item Total
MOUNT AND BALANCE (NO CHARGE) IN STOCK 1 N/C N/C
17X7.5 Silver Painted Sport Edition A7 IN STOCK 1 $104.00 $104.00
225/45HR17 Fuzion HRi IN STOCK 1 $68.00 $68.00
BS/FS WARRANTY PACKET IN STOCK 1 N/C N/C
BS/FS REGISTRATION CARD IN STOCK 1 N/C N/C
Sales Tax: $0.00
Excise Tax: $0.00
State Waste Tire Fund Fee: $0.00