235/75R17 vs 215/85R17
Going from one to the other changes the overall height by +1.7 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 235/75R17 | 215/85R17 | Change |
|---|---|---|---|
| Overall height | 30.9" | 31.4" | +1.7 % |
| Sidewall | 6.94" | 7.19" | +3.7 % |
| Section width | 235 mm | 215 mm | -8.5 % |
| Circumference | 97.0" | 98.6" | +1.7 % |
| Revs per mile | 653 | 643 | -1.7 % |
| Axle height | 15.44" | 15.69" | +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 235/75R17. Fit 215/85R17 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.5 mph | +0.5 |
| 50 mph | 50.8 mph | +0.8 |
| 70 mph | 71.2 mph | +1.2 |
| 90 mph | 91.5 mph | +1.5 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,166 on the road, so it under-counts by 166. At a true 70 mph the first turns 762 times a minute, the second 750.
What drivers reported
235/75R17 carries 8 complaints. Nobody has filed one naming 215/85R17.