235/75R15 vs 215/85R15
Going from one to the other changes the overall height by +1.8 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 235/75R15 | 215/85R15 | Change |
|---|---|---|---|
| Overall height | 28.9" | 29.4" | +1.8 % |
| Sidewall | 6.94" | 7.19" | +3.7 % |
| Section width | 235 mm | 215 mm | -8.5 % |
| Circumference | 90.7" | 92.3" | +1.8 % |
| Revs per mile | 698 | 686 | -1.8 % |
| Axle height | 14.44" | 14.69" | +6.5 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 235/75R15. Fit 215/85R15 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.5 mph | +0.5 |
| 50 mph | 50.9 mph | +0.9 |
| 70 mph | 71.2 mph | +1.2 |
| 90 mph | 91.6 mph | +1.6 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,177 on the road, so it under-counts by 177. At a true 70 mph the first turns 815 times a minute, the second 801.
What drivers reported
235/75R15 carries 219 complaints and 3 deaths. Nobody has filed one naming 215/85R15.