245/35R17 vs 235/35R17
Going from one to the other changes the overall height by -1.2 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 245/35R17 | 235/35R17 | Change |
|---|---|---|---|
| Overall height | 23.8" | 23.5" | -1.2 % |
| Sidewall | 3.38" | 3.24" | -4.1 % |
| Section width | 245 mm | 235 mm | -4.1 % |
| Circumference | 74.6" | 73.8" | -1.2 % |
| Revs per mile | 849 | 859 | +1.2 % |
| Axle height | 11.88" | 11.74" | -3.5 mm |
| Approved rim width | 7–9" | 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 245/35R17. Fit 235/35R17 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.7 mph | -0.3 |
| 50 mph | 49.4 mph | -0.6 |
| 70 mph | 69.2 mph | -0.8 |
| 90 mph | 89.0 mph | -1.0 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,884 on the road, so it over-counts by 116. At a true 70 mph the first turns 991 times a minute, the second 1002.