31x10.50R15 vs 235/75R15

31x10.50R15 is 2.1" taller than 235/75R15 (6.8%)

Diameter difference−6.85%diameter 31.00" → 28.88"
31x10.50R15235/75R15
31x10.50R15235/75R15Difference
Overall diameter31.00"28.88"−2.12"
Section width10.50"9.25"−1.25"
Sidewall height8.00"6.94"−1.06"
Circumference97.4"90.7"−6.7"
Revolutions per mile651698+48
Wheel diameter15"15"±0"

Speedometer

ShowsActualDiff
30 mph27.9 mph−2.1
45 mph41.9 mph−3.1
60 mph55.9 mph−4.1
70 mph65.2 mph−4.8
80 mph74.5 mph−5.5

Gear ratio to match

CurrentEquivalent
3.423.19
3.553.31
3.733.47
4.103.82

235/75R15 is 2.12" shorter than 31x10.50R15, a −6.85% change in diameter. That is more than the 3% many tire shops use as a limit, so plan on recalibrating the speedometer and checking ABS and stability control.

Ground clearance changes by 1.06" (half the diameter change), and the tire needs 1.06" less room above it.

31x10.50R15 is 1.25" wider. On the same wheel offset about half of that, 0.62", moves toward the suspension and half toward the fender.

Both fit a 15" wheel; the sidewall is 1.06" shorter on 235/75R15.

Details: 31x10.50R15 in inches · 235/75R15 in inches · change sizes in the calculator

FAQ

What is the difference between 31x10.50R15 and 235/75R15?

235/75R15 is 2.12" shorter (−6.85%) and 1.25" narrower than 31x10.50R15.

Will 235/75R15 change my speedometer?

Yes, by −6.85%. When the speedometer shows 60 mph you would be going 55.9 mph.

Can I replace 31x10.50R15 with 235/75R15?

It is a −6.8% diameter change, larger than the common 3% guideline, so check clearance and plan to recalibrate.