245/70R17 vs 255/65R17

245/70R17 is 0.5" taller than 255/65R17 (1.5%)

Diameter difference−1.48%diameter 30.50" → 30.05"
245/70R17255/65R17
245/70R17255/65R17Difference
Overall diameter30.50"30.05"−0.45"
Section width9.65"10.04"+0.39"
Sidewall height6.75"6.53"−0.23"
Circumference95.8"94.4"−1.4"
Revolutions per mile661671+10
Wheel diameter17"17"±0"

Speedometer

ShowsActualDiff
30 mph29.6 mph−0.4
45 mph44.3 mph−0.7
60 mph59.1 mph−0.9
70 mph69.0 mph−1.0
80 mph78.8 mph−1.2

Gear ratio to match

CurrentEquivalent
3.423.37
3.553.50
3.733.67
4.104.04

255/65R17 is 0.45" shorter than 245/70R17, a −1.48% change in diameter, inside the 3% range most shops treat as a safe swap.

Ground clearance changes by 0.23" (half the diameter change), and the tire needs 0.23" less room above it.

255/65R17 is 0.39" wider. On the same wheel offset about half of that, 0.20", moves toward the suspension and half toward the fender.

Both fit a 17" wheel; the sidewall is 0.23" shorter on 255/65R17.

Details: 245/70R17 in inches · 255/65R17 in inches · change sizes in the calculator

FAQ

What is the difference between 245/70R17 and 255/65R17?

255/65R17 is 0.45" shorter (−1.48%) and 0.39" wider than 245/70R17.

Will 255/65R17 change my speedometer?

Yes, by −1.48%. When the speedometer shows 60 mph you would be going 59.1 mph.

Can I replace 245/70R17 with 255/65R17?

Often yes: the diameter change of −1.5% is within the common 3% guideline. Check the load index, speed rating and clearance.