Home / Compare / 275/55R20 vs 285/55R20
275/55R20 vs 285/55R20 Tires: Size Difference
The 285/55R20 is 0.4 inches taller than the 275/55R20 (32.3 in against 31.9 in, +1.4%). At a displayed 60 mph on the speedometer you are really doing 60.8 mph. Edit either size below to compare something else.
1.4% taller overall: inside the common 3% guideline. Speedometer and odometer will be off by about the same percentage.
| Measure | Current 275/55R20 | New 285/55R20 | Difference |
|---|---|---|---|
| Overall diameter | 31.9 in (810 mm) | 32.3 in (822 mm) | +0.4 in (+1.4%) |
| Section width | 10.8 in (275 mm) | 11.2 in (285 mm) | +0.4 in (+10 mm) |
| Sidewall height | 6.0 in (151 mm) | 6.2 in (157 mm) | +0.2 in (+6 mm) |
| Circumference | 100.2 in | 101.6 in | +1.4 in (+1.4%) |
| Revolutions per mile | 632 | 624 | -8 (-1.3%) |
| Rim diameter | 20 in | 20 in | 0 in |
Ground clearance changes by about +0.2 in (+6 mm) at the axle, before load and tire flex.
| Speedometer shows (mph) | 30 | 45 | 60 | 70 | 80 |
|---|---|---|---|---|---|
| Actual speed (mph) | 30.4 | 45.6 | 60.8 | 71.0 | 81.1 |
| Speedometer shows (km/h) | 50 | 80 | 100 | 120 |
|---|---|---|---|---|
| Actual speed (km/h) | 50.7 | 81.1 | 101.4 | 121.6 |
Assumes the speedometer is accurate on the current size and reads from wheel rotation. Real speedometers can read a little high or low.
Estimates from the size codes only. This does not check whether the new size fits, rubs or is safe on your vehicle; ask a tire shop before you buy.
What changes between 275/55R20 and 285/55R20
- Diameter: 31.9 in becomes 32.3 in (+0.4 in, +1.4%). 1.4% taller overall: inside the common 3% guideline. Speedometer and odometer will be off by about the same percentage.
- Width: 275 mm (10.8 in) becomes 285 mm (11.2 in), a change of +10 mm.
- Sidewall: 151 mm (6.0 in) becomes 157 mm (6.2 in). A taller sidewall rides softer; a shorter one steers sharper.
- Revolutions per mile: 632 becomes 624, so the wheel turns 8 fewer times for every mile.
- Rim: 20 in and 20 in (the same wheel size).
Speedometer and odometer
With the 285/55R20 fitted and a speedometer set up for the 275/55R20, the dial no longer matches the road. The actual speed is the displayed speed multiplied by 32.3 / 31.9 = 1.014. The speedometer will read low by about 1.4% and the odometer will under-count distance by the same amount. Over 10,000 displayed miles you would really cover 10136 miles.
These figures assume the speedometer was accurate on the 275/55R20. A recalibration by a dealer or tuner can bring the dial back in line if the gap bothers you.
Will 285/55R20 fit instead of 275/55R20?
This page works out numbers from the size codes; it does not know your vehicle. Before you buy, check:
- The tire placard on the driver's door jamb for the approved sizes and the minimum load index and speed rating.
- Whether your wheel width suits a 285 mm tire. Every tire has an approved rim-width range.
- Clearance at full steering lock and over bumps, including the fender liner and suspension parts.
- If you change rim size, that brake calipers clear the new wheel.
The guide to reading a tire size explains every part of the code, and the pages for 275/55R20 and 285/55R20 give each size on its own.
More tire size comparisons
275/55R20 vs 285/55R20 FAQ
Is 285/55R20 bigger than 275/55R20?
Yes. The 285/55R20 is 32.3 inches tall against 31.9 inches for the 275/55R20, a difference of +0.4 inches (+1.4%). It is 10 mm wider than the 275/55R20.
How much will my speedometer be off going from 275/55R20 to 285/55R20?
If the speedometer is accurate on the 275/55R20, then at a displayed 60 mph you are doing 60.8 mph on the 285/55R20, and at a displayed 100 km/h you are doing 101.4 km/h. The odometer will differ by the same 1.4%.
Is the difference between 275/55R20 and 285/55R20 within the 3% rule?
Yes. The overall diameter differs by 1.4%, and the common guideline is about 3%. Staying within it keeps the speedometer error small but does not guarantee the tire will fit.
Will 285/55R20 rub where 275/55R20 does not?
That depends on your vehicle. The 285/55R20 is 10 mm wider and its sidewall is 6 mm taller. Wheel offset, wheel width, suspension and fender liners decide whether it rubs, so ask a tire shop.