275/55R20 vs 285/55R20

285/55R20 is 0.4" taller than 275/55R20 (1.4%)

Diameter difference+1.36%diameter 31.91" → 32.34"
275/55R20285/55R20
275/55R20285/55R20Difference
Overall diameter31.91"32.34"+0.43"
Section width10.83"11.22"+0.39"
Sidewall height5.95"6.17"+0.22"
Circumference100.2"101.6"+1.4"
Revolutions per mile632624−8
Wheel diameter20"20"±0"

Speedometer

ShowsActualDiff
30 mph30.4 mph+0.4
45 mph45.6 mph+0.6
60 mph60.8 mph+0.8
70 mph71.0 mph+1.0
80 mph81.1 mph+1.1

Gear ratio to match

CurrentEquivalent
3.423.47
3.553.60
3.733.78
4.104.16

285/55R20 is 0.43" taller than 275/55R20, a +1.36% change in diameter, inside the 3% range most shops treat as a safe swap.

Ground clearance changes by 0.22" (half the diameter change), and the tire needs 0.22" more room above it.

285/55R20 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 20" wheel; the sidewall is 0.22" taller on 285/55R20.

Details: 275/55R20 in inches · 285/55R20 in inches · change sizes in the calculator

FAQ

What is the difference between 275/55R20 and 285/55R20?

285/55R20 is 0.43" taller (+1.36%) and 0.39" wider than 275/55R20.

Will 285/55R20 change my speedometer?

Yes, by +1.36%. When the speedometer shows 60 mph you would be going 60.8 mph.

Can I replace 275/55R20 with 285/55R20?

Often yes: the diameter change of +1.4% is within the common 3% guideline. Check the load index, speed rating and clearance.