255/75R15 vs 235/75R15

255/75R15 is 1.2" taller than 235/75R15 (3.9%)

Diameter difference−3.93%diameter 30.06" → 28.88"
255/75R15235/75R15
255/75R15235/75R15Difference
Overall diameter30.06"28.88"−1.18"
Section width10.04"9.25"−0.79"
Sidewall height7.53"6.94"−0.59"
Circumference94.4"90.7"−3.7"
Revolutions per mile671698+27
Wheel diameter15"15"±0"

Speedometer

ShowsActualDiff
30 mph28.8 mph−1.2
45 mph43.2 mph−1.8
60 mph57.6 mph−2.4
70 mph67.2 mph−2.8
80 mph76.9 mph−3.1

Gear ratio to match

CurrentEquivalent
3.423.29
3.553.41
3.733.58
4.103.94

235/75R15 is 1.18" shorter than 255/75R15, a −3.93% 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 0.59" (half the diameter change), and the tire needs 0.59" less room above it.

255/75R15 is 0.79" wider. On the same wheel offset about half of that, 0.39", moves toward the suspension and half toward the fender.

Both fit a 15" wheel; the sidewall is 0.59" shorter on 235/75R15.

Details: 255/75R15 in inches · 235/75R15 in inches · change sizes in the calculator

FAQ

What is the difference between 255/75R15 and 235/75R15?

235/75R15 is 1.18" shorter (−3.93%) and 0.79" narrower than 255/75R15.

Will 235/75R15 change my speedometer?

Yes, by −3.93%. When the speedometer shows 60 mph you would be going 57.6 mph.

Can I replace 255/75R15 with 235/75R15?

It is a −3.9% diameter change, larger than the common 3% guideline, so check clearance and plan to recalibrate.