Most tires nowadays are marked with their contact pattern width (A), aspect ratio or tirewall height (B), and wheel diameter (C), to put it simply.
An example: 235 (A) / 75 (B)/ R15 (C)
Here we have a tire that has a 235mm nominal contact pattern width, aspect ratio of 75 and a rim diameter of 15 inches.
Aspect ratio determines the sidewall height of a tire, it's a percentage of the nominal contact pattern width. Regarding my example, an aspect ratio of 75 equals: 0.75*235= ~176 millimeters.
Another example: 275/60/R15
Contact pattern width is 275 millimetres, sidewall height is 165mm.
What that tells you, is that even though the 275/60R15 tire looks a lot bigger than the first example, it's actually smaller in diameter, yet wider.
If you intend to run skinny and tall tires such as the 235s, get 7 inch wheels. Low-profile, wider tires will look better on an 8" wheel. JMO.
[edit] damn, looks like i was typing too slowly
