315/40R20 vs 335/35R20
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 | 315/40R20 | 335/35R20 | Change |
|---|---|---|---|
| Overall height | 29.9" | 29.2" | -2.3 % |
| Sidewall | 4.96" | 4.62" | -6.9 % |
| Section width | 315 mm | 335 mm | +6.3 % |
| Circumference | 94.0" | 91.8" | -2.3 % |
| Revs per mile | 674 | 690 | +2.3 % |
| Axle height | 14.96" | 14.62" | -8.8 mm |
| Approved rim width | 8.5–11.5" | 9.5–12.5" | 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 315/40R20. Fit 335/35R20 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 9,770 on the road, so it over-counts by 230. At a true 70 mph the first turns 786 times a minute, the second 805.