225/80R15 vs 235/75R15
Going from one to the other changes the overall height by -1.0 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 225/80R15 | 235/75R15 | Change |
|---|---|---|---|
| Overall height | 29.2" | 28.9" | -1.0 % |
| Sidewall | 7.09" | 6.94" | -2.1 % |
| Section width | 225 mm | 235 mm | +4.4 % |
| Circumference | 91.7" | 90.7" | -1.0 % |
| Revs per mile | 691 | 698 | +1.0 % |
| Axle height | 14.59" | 14.44" | -3.8 mm |
| Approved rim width | 6–8.5" | 6.5–8.5" | 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 225/80R15. Fit 235/75R15 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.7 mph | -0.3 |
| 50 mph | 49.5 mph | -0.5 |
| 70 mph | 69.3 mph | -0.7 |
| 90 mph | 89.1 mph | -0.9 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,899 on the road, so it over-counts by 101. At a true 70 mph the first turns 807 times a minute, the second 815.
What drivers reported
Nobody has filed a complaint naming 225/80R15. 235/75R15 carries 219 and 3 deaths.