215/70R15 vs 235/60R15
Going from one to the other changes the overall height by -2.8 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 215/70R15 | 235/60R15 | Change |
|---|---|---|---|
| Overall height | 26.9" | 26.1" | -2.8 % |
| Sidewall | 5.93" | 5.55" | -6.3 % |
| Section width | 215 mm | 235 mm | +9.3 % |
| Circumference | 84.4" | 82.0" | -2.8 % |
| Revs per mile | 751 | 773 | +2.8 % |
| Axle height | 13.43" | 13.05" | -9.5 mm |
| Approved rim width | 6–8" | 6.5–8.5" | overlap 6.5–8" |
Both are approved on a rim 6.5" to 8" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 215/70R15. Fit 235/60R15 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.2 mph | -0.8 |
| 50 mph | 48.6 mph | -1.4 |
| 70 mph | 68.0 mph | -2.0 |
| 90 mph | 87.5 mph | -2.5 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,721 on the road, so it over-counts by 279. At a true 70 mph the first turns 876 times a minute, the second 901.