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Your 215/70-15 wheels/tires are 26.85" in overall diameter. So your question could be, if you swap to 17" wheels, what size tire would get you back to the same diameter? By going to a wider tread, but a smaller sidewall, you get back. Tire size calculators like the one at http://www.1010tires.com/tiresizecalculator.asp help you get the math done easily to compare tires. For example, a 245/50-17 has almost the same outer diameter as your current tire.

Do you know the width of the 17" wheel?

To determine the maximum tire width you can put on a given wheel, consider the wheel width. For example, my front wheels are 18" diameter x 8.5" width.

Tires are measured in mm of width, so 8.5" = 215.9 mm. My front tires are 255 mm, but that is actually the section width, or sidewall to sidewall, which is a bit wider than the

tread width. 8.5" wide wheels are a good fit for 255 mm tires.

It is actually a bit more complicated, because the tire's section width will change based on the width wheel the tire is mounted on. The section width quoted is for a 'measuring rim' for that tire.

Each tire normally has a recommended wheel size range. If we consult the Continental spec sheet for my tire, then it shows a wheel width of 8-9.5" is in range. Actually, a 8.5" wide rim was used for the measuring rim for their tire spec.

Also you have to consider what tires will fit with appropriate clearance when in place on the car of course.


2016 Cadillac ATS-V gray/black

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