235/70R23 vs 245/65R23
Going from one to the other changes the overall height by -1.1 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 235/70R23 | 245/65R23 | Change |
|---|---|---|---|
| Overall height | 36.0" | 35.5" | -1.1 % |
| Sidewall | 6.48" | 6.27" | -3.2 % |
| Section width | 235 mm | 245 mm | +4.3 % |
| Circumference | 112.9" | 111.7" | -1.1 % |
| Revs per mile | 561 | 567 | +1.1 % |
| Axle height | 17.98" | 17.77" | -5.3 mm |
| Approved rim width | 6.5–8.5" | 7–9" | 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 235/70R23. Fit 245/65R23 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 9,885 on the road, so it over-counts by 115. At a true 70 mph the first turns 654 times a minute, the second 662.