295/50R17 vs 285/55R17
Going from one to the other changes the overall height by +2.5 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 295/50R17 | 285/55R17 | Change |
|---|---|---|---|
| Overall height | 28.6" | 29.3" | +2.5 % |
| Sidewall | 5.81" | 6.17" | +6.3 % |
| Section width | 295 mm | 285 mm | -3.4 % |
| Circumference | 89.9" | 92.2" | +2.5 % |
| Revs per mile | 705 | 687 | -2.5 % |
| Axle height | 14.31" | 14.67" | +9.3 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 295/50R17. Fit 285/55R17 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.8 mph | +0.8 |
| 50 mph | 51.3 mph | +1.3 |
| 70 mph | 71.8 mph | +1.8 |
| 90 mph | 92.3 mph | +2.3 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,255 on the road, so it under-counts by 255. At a true 70 mph the first turns 822 times a minute, the second 802.