305/30R16 vs 295/30R16
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 | 305/30R16 | 295/30R16 | Change |
|---|---|---|---|
| Overall height | 23.2" | 23.0" | -1.0 % |
| Sidewall | 3.60" | 3.48" | -3.3 % |
| Section width | 305 mm | 295 mm | -3.3 % |
| Circumference | 72.9" | 72.2" | -1.0 % |
| Revs per mile | 869 | 878 | +1.0 % |
| Axle height | 11.60" | 11.48" | -3.0 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 305/30R16. Fit 295/30R16 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.7 mph | -0.3 |
| 50 mph | 49.5 mph | -0.5 |
| 70 mph | 69.3 mph | -0.7 |
| 90 mph | 89.1 mph | -0.9 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,898 on the road, so it over-counts by 102. At a true 70 mph the first turns 1014 times a minute, the second 1024.