235/70R17.5 vs 225/70R17.5
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 | 235/70R17.5 | 225/70R17.5 | Change |
|---|---|---|---|
| Overall height | 30.5" | 29.9" | -1.8 % |
| Sidewall | 6.48" | 6.20" | -4.3 % |
| Section width | 235 mm | 225 mm | -4.3 % |
| Circumference | 95.7" | 93.9" | -1.8 % |
| Revs per mile | 662 | 674 | +1.8 % |
| Axle height | 15.23" | 14.95" | -7.0 mm |
| Approved rim width | 6.5–8.5" | 6–8.5" | overlap 6.5–8.5" |
Both are approved on a rim 6.5" 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 235/70R17.5. Fit 225/70R17.5 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.5 mph | -0.5 |
| 50 mph | 49.1 mph | -0.9 |
| 70 mph | 68.7 mph | -1.3 |
| 90 mph | 88.4 mph | -1.6 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,819 on the road, so it over-counts by 181. At a true 70 mph the first turns 773 times a minute, the second 787.
What drivers reported
235/70R17.5 carries 2 complaints. Nobody has filed one naming 225/70R17.5.