265/30R15 vs 245/35R15
Going from one to the other changes the overall height by +2.3 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 265/30R15 | 245/35R15 | Change |
|---|---|---|---|
| Overall height | 21.3" | 21.8" | +2.3 % |
| Sidewall | 3.13" | 3.38" | +7.9 % |
| Section width | 265 mm | 245 mm | -7.5 % |
| Circumference | 66.8" | 68.3" | +2.3 % |
| Revs per mile | 949 | 927 | -2.3 % |
| Axle height | 10.63" | 10.88" | +6.3 mm |
| Approved rim width | 7.5–9.5" | 7–9" | overlap 7.5–9" |
Both are approved on a rim 7.5" to 9" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 265/30R15. Fit 245/35R15 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.7 mph | +0.7 |
| 50 mph | 51.2 mph | +1.2 |
| 70 mph | 71.6 mph | +1.6 |
| 90 mph | 92.1 mph | +2.1 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,231 on the road, so it under-counts by 231. At a true 70 mph the first turns 1107 times a minute, the second 1082.