315/65R17 vs 325/60R17
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 | 315/65R17 | 325/60R17 | Change |
|---|---|---|---|
| Overall height | 33.1" | 32.4" | -2.3 % |
| Sidewall | 8.06" | 7.68" | -4.8 % |
| Section width | 315 mm | 325 mm | +3.2 % |
| Circumference | 104.1" | 101.6" | -2.3 % |
| Revs per mile | 609 | 623 | +2.3 % |
| Axle height | 16.56" | 16.18" | -9.8 mm |
| Approved rim width | 8.5–11.5" | 9–12" | overlap 9–11.5" |
Both are approved on a rim 9" to 11.5" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 315/65R17. Fit 325/60R17 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.3 mph | -0.7 |
| 50 mph | 48.8 mph | -1.2 |
| 70 mph | 68.4 mph | -1.6 |
| 90 mph | 87.9 mph | -2.1 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,768 on the road, so it over-counts by 232. At a true 70 mph the first turns 710 times a minute, the second 727.