305/50R20 vs 295/55R20
Going from one to the other changes the overall height by +2.4 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 305/50R20 | 295/55R20 | Change |
|---|---|---|---|
| Overall height | 32.0" | 32.8" | +2.4 % |
| Sidewall | 6.00" | 6.39" | +6.4 % |
| Section width | 305 mm | 295 mm | -3.3 % |
| Circumference | 100.6" | 103.0" | +2.4 % |
| Revs per mile | 630 | 615 | -2.4 % |
| Axle height | 16.00" | 16.39" | +9.8 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 305/50R20. Fit 295/55R20 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.7 mph | +0.7 |
| 50 mph | 51.2 mph | +1.2 |
| 70 mph | 71.7 mph | +1.7 |
| 90 mph | 92.2 mph | +2.2 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,240 on the road, so it under-counts by 240. At a true 70 mph the first turns 735 times a minute, the second 718.
What drivers reported
305/50R20 carries 4 complaints. Nobody has filed one naming 295/55R20.