tommygunn

Recommended size is 245/45/18; with an alternative size of 225/50/18. This is according to Tire Rack.

Could I use 245/40/18?? I have been offered a deal on some Michelin Alpin snow tires, an after season clearance price on brand new tires.

Could I use these???

Stew4HD

Your speedometer will be off a bit and the tire will be thinner.

The 245 tells us it's 245 millimeters wide and the 45 tells us the sidewall height is 45% of 245 mm.

245 x .45 = 110.25 mm side wall

225 x .5 = 112.5 mm side wall

If I recall, to find out the over tire diameter, 18" converted to millimeters is (18 x 25.4) is 457.2mm

457.2 + (110.25 x 2) = 677.7mm OD (26.68") for the 245/42
457.2 + (112.5 x 2) = 682.2 mm OD (26.85") for the 225/50

so.. the 225/50 will work and the speedo will be a little off.. unless I missed something..... and to think I hated algrebra in school!

tommygunn

Thanks for the math lesson It looks like they will be slightly smaller in diameter. I talked to a friend of mine who is a race team mechanic. He thought I'll have no problems with this size. The speedo will be off slightly. The price is what is driving this

I have a MUCH better understanding of how this works.

Thanks again

jspagna1

This always comes in handy when I am shopping for tires and sizes.

http://www.1010tires.com/TireSizeCal...?action=submit

Just plug in the numbers and it should tell you what sizes will work.