245/50R15 vs 235/50R15
Going from one to the other changes the overall height by -1.6 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 245/50R15 | 235/50R15 | Change |
|---|---|---|---|
| Overall height | 24.6" | 24.3" | -1.6 % |
| Sidewall | 4.82" | 4.63" | -4.1 % |
| Section width | 245 mm | 235 mm | -4.1 % |
| Circumference | 77.4" | 76.2" | -1.6 % |
| Revs per mile | 818 | 832 | +1.6 % |
| Axle height | 12.32" | 12.13" | -5.0 mm |
| Approved rim width | 7–9" | 6.5–8.5" | overlap 7–8.5" |
Both are approved on a rim 7" to 8.5" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 245/50R15. Fit 235/50R15 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.5 mph | -0.5 |
| 50 mph | 49.2 mph | -0.8 |
| 70 mph | 68.9 mph | -1.1 |
| 90 mph | 88.6 mph | -1.4 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,840 on the road, so it over-counts by 160. At a true 70 mph the first turns 955 times a minute, the second 970.