255/40R18 vs 265/35R18

255/40R18 is 0.7" taller than 265/35R18 (2.8%)

Diameter difference−2.80%diameter 26.03" → 25.30"
255/40R18265/35R18
255/40R18265/35R18Difference
Overall diameter26.03"25.30"−0.73"
Section width10.04"10.43"+0.39"
Sidewall height4.02"3.65"−0.36"
Circumference81.8"79.5"−2.3"
Revolutions per mile775797+22
Wheel diameter18"18"±0"

Speedometer

ShowsActualDiff
30 mph29.2 mph−0.8
45 mph43.7 mph−1.3
60 mph58.3 mph−1.7
70 mph68.0 mph−2.0
80 mph77.8 mph−2.2

Gear ratio to match

CurrentEquivalent
3.423.32
3.553.45
3.733.63
4.103.99

265/35R18 is 0.73" shorter than 255/40R18, a −2.80% change in diameter, inside the 3% range most shops treat as a safe swap.

Ground clearance changes by 0.36" (half the diameter change), and the tire needs 0.36" less room above it.

265/35R18 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 18" wheel; the sidewall is 0.36" shorter on 265/35R18.

Details: 255/40R18 in inches · 265/35R18 in inches · change sizes in the calculator

FAQ

What is the difference between 255/40R18 and 265/35R18?

265/35R18 is 0.73" shorter (−2.80%) and 0.39" wider than 255/40R18.

Will 265/35R18 change my speedometer?

Yes, by −2.80%. When the speedometer shows 60 mph you would be going 58.3 mph.

Can I replace 255/40R18 with 265/35R18?

Often yes: the diameter change of −2.8% is within the common 3% guideline. Check the load index, speed rating and clearance.