295/55R20 vs 285/60R20
Going from one to the other changes the overall height by +2.1 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 295/55R20 | 285/60R20 | Change |
|---|---|---|---|
| Overall height | 32.8" | 33.5" | +2.1 % |
| Sidewall | 6.39" | 6.73" | +5.4 % |
| Section width | 295 mm | 285 mm | -3.4 % |
| Circumference | 103.0" | 105.1" | +2.1 % |
| Revs per mile | 615 | 603 | -2.1 % |
| Axle height | 16.39" | 16.73" | +8.8 mm |
| Approved rim width | 8.5–11" | 8–10.5" | overlap 8.5–10.5" |
Both are approved on a rim 8.5" to 10.5" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 295/55R20. Fit 285/60R20 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.6 mph | +0.6 |
| 50 mph | 51.1 mph | +1.1 |
| 70 mph | 71.5 mph | +1.5 |
| 90 mph | 91.9 mph | +1.9 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,210 on the road, so it under-counts by 210. At a true 70 mph the first turns 718 times a minute, the second 703.
What drivers reported
Nobody has filed a complaint naming 295/55R20. 285/60R20 carries 10.