is there a url where i can input a wheel/tire size and it will calculate what the next plus size up is automatically? if tire rack has it, i can't seem to find it.

 

Use the powerdog tire calculator here. It lets you enter a whole bunch of different sizes and compares the outside diameter of all of them to the first one you list. Play around with it and you'll find the size you need.

 

this is another one
http://www.mr2.com/FORMS/tire.html

 

Try this one http://www.miata.net/garage/tirecalc.html

 

And yet another... http://pw1.netcom.com/~sgalaba/tiresize.htm#TireSize




[Modified by FAST4DR, 6:14 PM 7/26/2001]