305/35R24 vs 315/30R24
Going from one to the other changes the overall height by -3.0 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 305/35R24 | 315/30R24 | Change |
|---|---|---|---|
| Overall height | 32.4" | 31.4" | -3.0 % |
| Sidewall | 4.20" | 3.72" | -11.5 % |
| Section width | 305 mm | 315 mm | +3.3 % |
| Circumference | 101.8" | 98.8" | -3.0 % |
| Revs per mile | 622 | 641 | +3.0 % |
| Axle height | 16.20" | 15.72" | -12.3 mm |
| Approved rim width | 8.5–11" | 8.5–11.5" | overlap 8.5–11" |
Both are approved on a rim 8.5" to 11" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 305/35R24. Fit 315/30R24 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.1 mph | -0.9 |
| 50 mph | 48.5 mph | -1.5 |
| 70 mph | 67.9 mph | -2.1 |
| 90 mph | 87.3 mph | -2.7 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,702 on the road, so it over-counts by 298. At a true 70 mph the first turns 726 times a minute, the second 748.
What drivers reported
305/35R24 carries 1 complaints. Nobody has filed one naming 315/30R24.