I was hoping someone could tell me the pros and cons of mounting 31" tires on 15" rims as apposed to 16". Obviously the side wall is taller but is that necessarily a bad thing?

 

Taller side wall was my only reason to go with 15s on 31's.

 

15's are also cheaper to buy the wheels and the tires that go on them. Plus i like the look of a smaller wheel better.

 

Depends what you want...
15" rim equals more sidewall flex than the 16"
15" rim equals less expensive tires than the 16"
15" rim equals more common tires than the 16"

...need I say more?

Anywho, performance wise, they're close enough that you won't notice. But you will save on price.

BTW, what kinda rig is this going on...? Some newer ones have trouble fitting 15", so 16" might be your only option.

Jim