255/70R18 vs 275/65R18

275/65R18 is 0.0" taller than 255/70R18 (0.1%)

Diameter difference+0.06%diameter 32.06" → 32.07"
255/70R18275/65R18
255/70R18275/65R18Difference
Overall diameter32.06"32.07"+0.02"
Section width10.04"10.83"+0.79"
Sidewall height7.03"7.04"+0.01"
Circumference100.7"100.8"+0.1"
Revolutions per mile629629−0
Wheel diameter18"18"±0"

Speedometer

ShowsActualDiff
30 mph30.0 mph+0.0
45 mph45.0 mph+0.0
60 mph60.0 mph+0.0
70 mph70.0 mph+0.0
80 mph80.0 mph+0.0

Gear ratio to match

CurrentEquivalent
3.423.42
3.553.55
3.733.73
4.104.10

275/65R18 is 0.02" taller than 255/70R18, a +0.06% change in diameter, inside the 3% range most shops treat as a safe swap.

Ground clearance changes by 0.01" (half the diameter change), and the tire needs 0.01" more room above it.

275/65R18 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 18" wheel; the sidewall is 0.01" taller on 275/65R18.

Details: 255/70R18 in inches · 275/65R18 in inches · change sizes in the calculator

FAQ

What is the difference between 255/70R18 and 275/65R18?

275/65R18 is 0.02" taller (+0.06%) and 0.79" wider than 255/70R18.

Will 275/65R18 change my speedometer?

Yes, by +0.06%. When the speedometer shows 60 mph you would be going 60.0 mph.

Can I replace 255/70R18 with 275/65R18?

Often yes: the diameter change of +0.1% is within the common 3% guideline. Check the load index, speed rating and clearance.