235/80R17 vs 215/85R17
Going from one to the other changes the overall height by -1.3 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 235/80R17 | 215/85R17 | Change |
|---|---|---|---|
| Overall height | 31.8" | 31.4" | -1.3 % |
| Sidewall | 7.40" | 7.19" | -2.8 % |
| Section width | 235 mm | 215 mm | -8.5 % |
| Circumference | 99.9" | 98.6" | -1.3 % |
| Revs per mile | 634 | 643 | +1.3 % |
| Axle height | 15.90" | 15.69" | -5.3 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 235/80R17. Fit 215/85R17 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.6 mph | -0.4 |
| 50 mph | 49.4 mph | -0.6 |
| 70 mph | 69.1 mph | -0.9 |
| 90 mph | 88.8 mph | -1.2 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,870 on the road, so it over-counts by 130. At a true 70 mph the first turns 740 times a minute, the second 750.
What drivers reported
235/80R17 carries 17 complaints. Nobody has filed one naming 215/85R17.