255/35R20 vs 275/35R20

275/35R20 is 0.6" taller than 255/35R20 (2.0%)

Diameter difference+2.04%diameter 27.03" → 27.58"
255/35R20275/35R20
255/35R20275/35R20Difference
Overall diameter27.03"27.58"+0.55"
Section width10.04"10.83"+0.79"
Sidewall height3.51"3.79"+0.28"
Circumference84.9"86.6"+1.7"
Revolutions per mile746731−15
Wheel diameter20"20"±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

275/35R20 is 0.55" taller than 255/35R20, a +2.04% change in diameter, inside the 3% range most shops treat as a safe swap.

Ground clearance changes by 0.28" (half the diameter change), and the tire needs 0.28" more room above it.

275/35R20 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 20" wheel; the sidewall is 0.28" taller on 275/35R20.

Details: 255/35R20 in inches · 275/35R20 in inches · change sizes in the calculator

FAQ

What is the difference between 255/35R20 and 275/35R20?

275/35R20 is 0.55" taller (+2.04%) and 0.79" wider than 255/35R20.

Will 275/35R20 change my speedometer?

Yes, by +2.04%. When the speedometer shows 60 mph you would be going 61.2 mph.

Can I replace 255/35R20 with 275/35R20?

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