255/80R17 vs 285/70R17

255/80R17 is 0.4" taller than 285/70R17 (1.1%)

Diameter difference−1.07%diameter 33.06" → 32.71"
255/80R17285/70R17
255/80R17285/70R17Difference
Overall diameter33.06"32.71"−0.35"
Section width10.04"11.22"+1.18"
Sidewall height8.03"7.85"−0.18"
Circumference103.9"102.8"−1.1"
Revolutions per mile610617+7
Wheel diameter17"17"±0"

Speedometer

ShowsActualDiff
30 mph29.7 mph−0.3
45 mph44.5 mph−0.5
60 mph59.4 mph−0.6
70 mph69.2 mph−0.8
80 mph79.1 mph−0.9

Gear ratio to match

CurrentEquivalent
3.423.38
3.553.51
3.733.69
4.104.06

285/70R17 is 0.35" shorter than 255/80R17, a −1.07% change in diameter, inside the 3% range most shops treat as a safe swap.

Ground clearance changes by 0.18" (half the diameter change), and the tire needs 0.18" less 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 0.18" shorter on 285/70R17.

Details: 255/80R17 in inches · 285/70R17 in inches · change sizes in the calculator

FAQ

What is the difference between 255/80R17 and 285/70R17?

285/70R17 is 0.35" shorter (−1.07%) and 1.18" wider than 255/80R17.

Will 285/70R17 change my speedometer?

Yes, by −1.07%. When the speedometer shows 60 mph you would be going 59.4 mph.

Can I replace 255/80R17 with 285/70R17?

Often yes: the diameter change of −1.1% is within the common 3% guideline. Check the load index, speed rating and clearance.