245/35R23 vs 265/30R23
Going from one to the other changes the overall height by -1.7 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 245/35R23 | 265/30R23 | Change |
|---|---|---|---|
| Overall height | 29.8" | 29.3" | -1.7 % |
| Sidewall | 3.38" | 3.13" | -7.3 % |
| Section width | 245 mm | 265 mm | +8.2 % |
| Circumference | 93.5" | 91.9" | -1.7 % |
| Revs per mile | 678 | 689 | +1.7 % |
| Axle height | 14.88" | 14.63" | -6.3 mm |
| Approved rim width | 7–9" | 7.5–9.5" | 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 245/35R23. Fit 265/30R23 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.5 mph | -0.5 |
| 50 mph | 49.2 mph | -0.8 |
| 70 mph | 68.8 mph | -1.2 |
| 90 mph | 88.5 mph | -1.5 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,835 on the road, so it over-counts by 165. At a true 70 mph the first turns 791 times a minute, the second 804.