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185/60-14 - what I have on donuts
195/50-15 - this would be the highest rim/tire size I would go*
205/40-16
205/40-17
215/35-18

*high performance tires = $$$, rims = $$$, the combo = target for theft
(185/60-14 on donuts: relatively inexpensive, good performance, no one looks twice at them)