235/35R15 vs 215/35R15
Going from one to the other changes the overall height by -2.6 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 235/35R15 | 215/35R15 | Change |
|---|---|---|---|
| Overall height | 21.5" | 20.9" | -2.6 % |
| Sidewall | 3.24" | 2.96" | -8.5 % |
| Section width | 235 mm | 215 mm | -8.5 % |
| Circumference | 67.5" | 65.7" | -2.6 % |
| Revs per mile | 939 | 964 | +2.6 % |
| Axle height | 10.74" | 10.46" | -7.0 mm |
| Approved rim width | 6.5–8.5" | 6–8" | 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 235/35R15. Fit 215/35R15 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.2 mph | -0.8 |
| 50 mph | 48.7 mph | -1.3 |
| 70 mph | 68.2 mph | -1.8 |
| 90 mph | 87.7 mph | -2.3 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,743 on the road, so it over-counts by 257. At a true 70 mph the first turns 1096 times a minute, the second 1124.