255/70R15 vs 235/75R15

255/70R15 is 0.2" taller than 235/75R15 (0.6%)

Diameter difference−0.61%diameter 29.06" → 28.88"
255/70R15235/75R15
255/70R15235/75R15Difference
Overall diameter29.06"28.88"−0.18"
Section width10.04"9.25"−0.79"
Sidewall height7.03"6.94"−0.09"
Circumference91.3"90.7"−0.6"
Revolutions per mile694698+4
Wheel diameter15"15"±0"

Speedometer

ShowsActualDiff
30 mph29.8 mph−0.2
45 mph44.7 mph−0.3
60 mph59.6 mph−0.4
70 mph69.6 mph−0.4
80 mph79.5 mph−0.5

Gear ratio to match

CurrentEquivalent
3.423.40
3.553.53
3.733.71
4.104.07

235/75R15 is 0.18" shorter than 255/70R15, a −0.61% change in diameter, inside the 3% range most shops treat as a safe swap.

Ground clearance changes by 0.09" (half the diameter change), and the tire needs 0.09" less room above it.

255/70R15 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 0.09" shorter on 235/75R15.

Details: 255/70R15 in inches · 235/75R15 in inches · change sizes in the calculator

FAQ

What is the difference between 255/70R15 and 235/75R15?

235/75R15 is 0.18" shorter (−0.61%) and 0.79" narrower than 255/70R15.

Will 235/75R15 change my speedometer?

Yes, by −0.61%. When the speedometer shows 60 mph you would be going 59.6 mph.

Can I replace 255/70R15 with 235/75R15?

Often yes: the diameter change of −0.6% is within the common 3% guideline. Check the load index, speed rating and clearance.