225/70R17 vs 245/65R17
Going from one to the other changes the overall height by +0.5 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 225/70R17 | 245/65R17 | Change |
|---|---|---|---|
| Overall height | 29.4" | 29.5" | +0.5 % |
| Sidewall | 6.20" | 6.27" | +1.1 % |
| Section width | 225 mm | 245 mm | +8.9 % |
| Circumference | 92.4" | 92.8" | +0.5 % |
| Revs per mile | 686 | 683 | -0.5 % |
| Axle height | 14.70" | 14.77" | +1.8 mm |
| Approved rim width | 6–8.5" | 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 225/70R17. Fit 245/65R17 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.1 mph | +0.1 |
| 50 mph | 50.2 mph | +0.2 |
| 70 mph | 70.3 mph | +0.3 |
| 90 mph | 90.4 mph | +0.4 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,047 on the road, so it under-counts by 47. At a true 70 mph the first turns 800 times a minute, the second 797.