I have 17x9.5 wheels on my car right now and I want Nitto 555Rs to put on soon and I was wondering what size is best. But instead of just telling me 315/40/17 or what ever it is. Could someone explain to me what those numbers mean so I don't ever have to bother the board again

"Give a man a fish he'll eat for a day. Teach a man to fish and he'll eat tires forever... er fish."

 

As I understand it:
315 is the width of the tire in millimeters,
40 is the aspect ratio. That means the sidewall is 40% of the width of the tire
17 is the diameter of the wheel
Hope that helps you

 

How do those numbers relate to performance? Such as why would I choose one size over the other?

 

Here it is graphically compliments of Discount Tire Online:


http://www.discounttiredirect.com/he...imensions.html


Britt

 

when it comes to tires, everything is a trade off.
A bigger contact patch (wider tire) will get better traction if you are racing, but it also raises your rolling resistance and will decrease your fuel economy. If you drive in snow at all, a wider tire will make it even worse to drive. Your tire choice depends a lot on your needs. Certain sidewall heights are better for road racing and different sidewalls are better for drag racing. I am not sure when it comes to racing, but when it comes to everyday driving, a larger diameter wheel gives a rougher ride. low profile tires look good, but the lack of flex in the sidewall also makes them ride rougher. So basically, what size tires to get is dependant on how you plan to use the car.