Go look at the tire manufactures website. Every tire is different. Just becuase it says its a 31" tires doesn't mean it measures 31". Each tire is different. You have to check with the tire manufacture to get the tire specs.

 

ok sorry about all this but one last question whats the differance between 245/45/20 and 255/45/20 and will the 245/45/20 fit

 

Ok... Now to type this again (stupid firefox crash)...

I agree with Hanr3 on the tire size. These numbers are nominal numbers and they vary manufacturer to manufacturer.

Anyway, a 245/45R20 will be a ~28.7" diameter tire with 703 rev/mile while the 255/45R20 tire having a 29" diameter with 695rev/mile. The 255 tire is also 10mm (~0.4') wider than the 245 tire.

To break down the metric nomenclature for you:
Lets examine the 245/45R20 tire...
The first number, 245, is the tread width in millimeters. 245mm = ~9.645inches
The second number is the percentage of sidewall height to treadwidth. So for a 45 series tire, the sidewall height would be 245 (treadwidth) * 45 / 100 = 110.25mm (~4.34inches).
The third number is the rim diameter.
To get the overall diameter of the tire, you have to add up all of the heights. So double the sidewall height and add in the rim diameter and you'll get the overall height. Again for the 245/45R20, the overall height would be 4.34+4.34+20 or ~28.7"

Good luck and any more questions, just post away.

 

ok ahha so i can find another question to ask u ho big is the sidewall on a 245/35/20 tire

 

245*35/100 = 85.75mm (3.38in)

 

thanks for the help...so in your eyes is there a very noticeable size in sidewall increase that a normal eye would see because i want to fill the wheelwell as best as i can without dropping it