255/40R17 vs 275/40R17

275/40R17 is 0.6" taller than 255/40R17 (2.5%)

Diameter difference+2.52%diameter 25.03" → 25.66"
255/40R17275/40R17
255/40R17275/40R17Difference
Overall diameter25.03"25.66"+0.63"
Section width10.04"10.83"+0.79"
Sidewall height4.02"4.33"+0.31"
Circumference78.6"80.6"+2.0"
Revolutions per mile806786−20
Wheel diameter17"17"±0"

Speedometer

ShowsActualDiff
30 mph30.8 mph+0.8
45 mph46.1 mph+1.1
60 mph61.5 mph+1.5
70 mph71.8 mph+1.8
80 mph82.0 mph+2.0

Gear ratio to match

CurrentEquivalent
3.423.51
3.553.64
3.733.82
4.104.20

275/40R17 is 0.63" taller than 255/40R17, a +2.52% change in diameter, inside the 3% range most shops treat as a safe swap.

Ground clearance changes by 0.31" (half the diameter change), and the tire needs 0.31" more room above it.

275/40R17 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 0.31" taller on 275/40R17.

Details: 255/40R17 in inches · 275/40R17 in inches · change sizes in the calculator

FAQ

What is the difference between 255/40R17 and 275/40R17?

275/40R17 is 0.63" taller (+2.52%) and 0.79" wider than 255/40R17.

Will 275/40R17 change my speedometer?

Yes, by +2.52%. When the speedometer shows 60 mph you would be going 61.5 mph.

Can I replace 255/40R17 with 275/40R17?

Often yes: the diameter change of +2.5% is within the common 3% guideline. Check the load index, speed rating and clearance.