275/70R18 vs 285/70R18

285/70R18 is 0.6" taller than 275/70R18 (1.7%)

Diameter difference+1.66%diameter 33.16" → 33.71"
275/70R18285/70R18
275/70R18285/70R18Difference
Overall diameter33.16"33.71"+0.55"
Section width10.83"11.22"+0.39"
Sidewall height7.58"7.85"+0.28"
Circumference104.2"105.9"+1.7"
Revolutions per mile608598−10
Wheel diameter18"18"±0"

Speedometer

ShowsActualDiff
30 mph30.5 mph+0.5
45 mph45.7 mph+0.7
60 mph61.0 mph+1.0
70 mph71.2 mph+1.2
80 mph81.3 mph+1.3

Gear ratio to match

CurrentEquivalent
3.423.48
3.553.61
3.733.79
4.104.17

285/70R18 is 0.55" taller than 275/70R18, a +1.66% 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.

285/70R18 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 0.28" taller on 285/70R18.

Details: 275/70R18 in inches · 285/70R18 in inches · change sizes in the calculator

FAQ

What is the difference between 275/70R18 and 285/70R18?

285/70R18 is 0.55" taller (+1.66%) and 0.39" wider than 275/70R18.

Will 285/70R18 change my speedometer?

Yes, by +1.66%. When the speedometer shows 60 mph you would be going 61.0 mph.

Can I replace 275/70R18 with 285/70R18?

Often yes: the diameter change of +1.7% is within the common 3% guideline. Check the load index, speed rating and clearance.