255/55R17 vs 235/60R17
Going from one to the other changes the overall height by +0.2 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 255/55R17 | 235/60R17 | Change |
|---|---|---|---|
| Overall height | 28.0" | 28.1" | +0.2 % |
| Sidewall | 5.52" | 5.55" | +0.5 % |
| Section width | 255 mm | 235 mm | -7.8 % |
| Circumference | 88.1" | 88.3" | +0.2 % |
| Revs per mile | 719 | 718 | -0.2 % |
| Axle height | 14.02" | 14.05" | +0.8 mm |
| Approved rim width | 7–9.5" | 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 255/55R17. Fit 235/60R17 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.1 mph | +0.1 |
| 50 mph | 50.1 mph | +0.1 |
| 70 mph | 70.1 mph | +0.1 |
| 90 mph | 90.2 mph | +0.2 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,021 on the road, so it under-counts by 21. At a true 70 mph the first turns 839 times a minute, the second 837.
What drivers reported
Nobody has filed a complaint naming 255/55R17. 235/60R17 carries 18.