whats the difference in tires between 225/40/18 and 215/40/18... i dont know what to get cuz i dont know the difference? do the rims have to do anything with size?

 

Small difference in outer tread diameter, 225 is both wider and taller. So consider the error of your speedometer as well as fender clearance on your car. (WHAT car?)

Go to tirerack.com & look at tire specs. For each size, it will list the wheel width range that will work. Make sure your rims have the proper width.

 

Approx 3/4" wider than the other..that is all...

 

but ang im pretty sure 3/4 of an inch makes a big difference in grip. i mean multiply it by 4 tires...u get 3 inches extra on the road. lots more rubber. ur prob right but in my opinion thats worth thextra 100 for the set
I mean im upgrading from 235/45/18 to 245/40/18 for my next set, and im paying an extra 20 a tire. but to me, these tires are so worth it.

Michelin Pilot Sport PS2 YEA!!!!

 

But 10mm is less than 1/2 inch.