255/80R17 vs 275/70R17

255/80R17 is 0.9" taller than 275/70R17 (2.7%)

Diameter difference−2.74%diameter 33.06" → 32.16"
255/80R17275/70R17
255/80R17275/70R17Difference
Overall diameter33.06"32.16"−0.91"
Section width10.04"10.83"+0.79"
Sidewall height8.03"7.58"−0.45"
Circumference103.9"101.0"−2.8"
Revolutions per mile610627+17
Wheel diameter17"17"±0"

Speedometer

ShowsActualDiff
30 mph29.2 mph−0.8
45 mph43.8 mph−1.2
60 mph58.4 mph−1.6
70 mph68.1 mph−1.9
80 mph77.8 mph−2.2

Gear ratio to match

CurrentEquivalent
3.423.33
3.553.45
3.733.63
4.103.99

275/70R17 is 0.91" shorter than 255/80R17, a −2.74% change in diameter, inside the 3% range most shops treat as a safe swap.

Ground clearance changes by 0.45" (half the diameter change), and the tire needs 0.45" less room above it.

275/70R17 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 17" wheel; the sidewall is 0.45" shorter on 275/70R17.

Details: 255/80R17 in inches · 275/70R17 in inches · change sizes in the calculator

FAQ

What is the difference between 255/80R17 and 275/70R17?

275/70R17 is 0.91" shorter (−2.74%) and 0.79" wider than 255/80R17.

Will 275/70R17 change my speedometer?

Yes, by −2.74%. When the speedometer shows 60 mph you would be going 58.4 mph.

Can I replace 255/80R17 with 275/70R17?

Often yes: the diameter change of −2.7% is within the common 3% guideline. Check the load index, speed rating and clearance.