335/45R24 vs 315/45R24
Going from one to the other changes the overall height by -2.0 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 335/45R24 | 315/45R24 | Change |
|---|---|---|---|
| Overall height | 35.9" | 35.2" | -2.0 % |
| Sidewall | 5.94" | 5.58" | -6.0 % |
| Section width | 335 mm | 315 mm | -6.0 % |
| Circumference | 112.7" | 110.5" | -2.0 % |
| Revs per mile | 562 | 574 | +2.0 % |
| Axle height | 17.94" | 17.58" | -9.0 mm |
| Approved rim width | 9.5–12.5" | 8.5–11.5" | overlap 9.5–11.5" |
Both are approved on a rim 9.5" 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 335/45R24. Fit 315/45R24 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.4 mph | -0.6 |
| 50 mph | 49.0 mph | -1.0 |
| 70 mph | 68.6 mph | -1.4 |
| 90 mph | 88.2 mph | -1.8 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,802 on the road, so it over-counts by 198. At a true 70 mph the first turns 656 times a minute, the second 669.