295/60R20 vs 305/55R20
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 | 295/60R20 | 305/55R20 | Change |
|---|---|---|---|
| Overall height | 33.9" | 33.2" | -2.1 % |
| Sidewall | 6.97" | 6.60" | -5.2 % |
| Section width | 295 mm | 305 mm | +3.4 % |
| Circumference | 106.6" | 104.3" | -2.1 % |
| Revs per mile | 594 | 607 | +2.1 % |
| Axle height | 16.97" | 16.60" | -9.3 mm |
| Approved rim width | 8.5–11" | 8.5–11" | overlap 8.5–11" |
Both are approved on a rim 8.5" to 11" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 295/60R20. Fit 305/55R20 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.4 mph | -0.6 |
| 50 mph | 48.9 mph | -1.1 |
| 70 mph | 68.5 mph | -1.5 |
| 90 mph | 88.1 mph | -1.9 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,785 on the road, so it over-counts by 215. At a true 70 mph the first turns 693 times a minute, the second 709.
What drivers reported
Nobody has filed a complaint naming 295/60R20. 305/55R20 carries 1.