285/30R17 vs 295/30R17
Going from one to the other changes the overall height by +1.0 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 285/30R17 | 295/30R17 | Change |
|---|---|---|---|
| Overall height | 23.7" | 24.0" | +1.0 % |
| Sidewall | 3.37" | 3.48" | +3.5 % |
| Section width | 285 mm | 295 mm | +3.5 % |
| Circumference | 74.6" | 75.3" | +1.0 % |
| Revs per mile | 850 | 841 | -1.0 % |
| Axle height | 11.87" | 11.98" | +3.0 mm |
| Approved rim width | 8–10.5" | 8.5–11" | 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 285/30R17. Fit 295/30R17 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.3 mph | +0.3 |
| 50 mph | 50.5 mph | +0.5 |
| 70 mph | 70.7 mph | +0.7 |
| 90 mph | 90.9 mph | +0.9 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,100 on the road, so it under-counts by 100. At a true 70 mph the first turns 991 times a minute, the second 982.