255/75R17 vs 285/70R17

285/70R17 is 0.6" taller than 255/75R17 (2.0%)

Diameter difference+2.03%diameter 32.06" → 32.71"
255/75R17285/70R17
255/75R17285/70R17Difference
Overall diameter32.06"32.71"+0.65"
Section width10.04"11.22"+1.18"
Sidewall height7.53"7.85"+0.32"
Circumference100.7"102.8"+2.0"
Revolutions per mile629617−12
Wheel diameter17"17"±0"

Speedometer

ShowsActualDiff
30 mph30.6 mph+0.6
45 mph45.9 mph+0.9
60 mph61.2 mph+1.2
70 mph71.4 mph+1.4
80 mph81.6 mph+1.6

Gear ratio to match

CurrentEquivalent
3.423.49
3.553.62
3.733.81
4.104.18

285/70R17 is 0.65" taller than 255/75R17, a +2.03% change in diameter, inside the 3% range most shops treat as a safe swap.

Ground clearance changes by 0.32" (half the diameter change), and the tire needs 0.32" more room above it.

285/70R17 is 1.18" wider. On the same wheel offset about half of that, 0.59", moves toward the suspension and half toward the fender.

Both fit a 17" wheel; the sidewall is 0.32" taller on 285/70R17.

Details: 255/75R17 in inches · 285/70R17 in inches · change sizes in the calculator

FAQ

What is the difference between 255/75R17 and 285/70R17?

285/70R17 is 0.65" taller (+2.03%) and 1.18" wider than 255/75R17.

Will 285/70R17 change my speedometer?

Yes, by +2.03%. When the speedometer shows 60 mph you would be going 61.2 mph.

Can I replace 255/75R17 with 285/70R17?

Often yes: the diameter change of +2.0% is within the common 3% guideline. Check the load index, speed rating and clearance.