I have GMC terrain SLE2 trim 2015 model with R17 225/60 tyres as manufacturer recommendation. When I bought this car, it was installed with 275/40 R20 tyre. However, now its time for for tyre change, Whats the recommended tyre size with R20 rim ?

Also note Top Level Trim Denali GMC terrain 2015 has 245/45 R20 tyres. So I feel it should be Ok to put same tyre size. Please share your thoughts.

1 Answer 1


This is a useful resource when choosing tire sizes:

Tire Size Calculator

Comparing the two sizes you mentioned gives this:

Size Comparison

Note that the R20 tire, overall, is just a bit larger than the R17 tires. So clearance-wise it should not be a problem.

You do realize, however, that the number following the "R" is the rim or wheel diameter and you cannot put R20 tires on a 17" rim or R17 tires on a 20" rim. So to change sizes you will need to replace your rims/wheels.

  • The "R" actually denotes "radial", meaning it's a radial tire. It was to differentiate them from bias plies which don't have a designation there. Mar 3, 2023 at 12:26
  • 1
    R20 is 20" rim size, R17 is 17". But you are correct, "R" means radial. I'm not sure it's relevant to this question though.
    – jwh20
    Mar 3, 2023 at 12:59
  • Just pointing it out as you seem to be confused. I want to ensure nobody else is. Mar 3, 2023 at 13:22

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