Copy and paste this ; Tirerack.com Hope they answer your questions...
All the tires should be the same size. If the other tires are in place you should be able to get the size from the other tires. If not the size should be on a plate inside the drivers side door with many other specs.
of course
First off you should not install tires that are not the correct size. But if you do, make sure the tires on each axle are both the same size. Both front tires same size, and both rear tires same size.
same size as the other tires on your van,
Tires come in every possible size you could imagine.
I suggest you go to www.tirerack.com You will find the correct answer there.
Tires Size - 215/60/R15" Rim Size - 15 inches
form_title= Tire Size Calculator form_header= Drive with the right size tires Want size tires do you currently have?*= _ [50] When were your tires last replaced?*= _ [50] Do you want to change tire size?*= () Yes () No
15 inch tires the exact size was 215/75R15
form_title= Tire Size form_header= Drive like a pro with new tires. Want size tires do you currently have?*= _ [50] When were your tires last replaced?*= _ [50] Do you want to change tire size?*= () Yes () No
If all four tires on an MTB bicycle are 26 by 2.10, they are the same size.