285/35R20 vs 275/35R20

285/35R20 is 0.3" taller than 275/35R20 (1.0%)

Diameter difference−0.99%diameter 27.85" → 27.58"
285/35R20275/35R20
285/35R20275/35R20Difference
Overall diameter27.85"27.58"−0.28"
Section width11.22"10.83"−0.39"
Sidewall height3.93"3.79"−0.14"
Circumference87.5"86.6"−0.9"
Revolutions per mile724731+7
Wheel diameter20"20"±0"

Speedometer

ShowsActualDiff
30 mph29.7 mph−0.3
45 mph44.6 mph−0.4
60 mph59.4 mph−0.6
70 mph69.3 mph−0.7
80 mph79.2 mph−0.8

Gear ratio to match

CurrentEquivalent
3.423.39
3.553.51
3.733.69
4.104.06

275/35R20 is 0.28" shorter than 285/35R20, a −0.99% change in diameter, inside the 3% range most shops treat as a safe swap.

Ground clearance changes by 0.14" (half the diameter change), and the tire needs 0.14" less room above it.

285/35R20 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 0.14" shorter on 275/35R20.

Details: 285/35R20 in inches · 275/35R20 in inches · change sizes in the calculator

FAQ

What is the difference between 285/35R20 and 275/35R20?

275/35R20 is 0.28" shorter (−0.99%) and 0.39" narrower than 285/35R20.

Will 275/35R20 change my speedometer?

Yes, by −0.99%. When the speedometer shows 60 mph you would be going 59.4 mph.

Can I replace 285/35R20 with 275/35R20?

Often yes: the diameter change of −1.0% is within the common 3% guideline. Check the load index, speed rating and clearance.