315/60R20 vs 335/60R20
Going from one to the other changes the overall height by +2.7 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 315/60R20 | 335/60R20 | Change |
|---|---|---|---|
| Overall height | 34.9" | 35.8" | +2.7 % |
| Sidewall | 7.44" | 7.91" | +6.3 % |
| Section width | 315 mm | 335 mm | +6.3 % |
| Circumference | 109.6" | 112.6" | +2.7 % |
| Revs per mile | 578 | 563 | -2.7 % |
| Axle height | 17.44" | 17.91" | +12.0 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 315/60R20. Fit 335/60R20 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.8 mph | +0.8 |
| 50 mph | 51.4 mph | +1.4 |
| 70 mph | 71.9 mph | +1.9 |
| 90 mph | 92.4 mph | +2.4 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,271 on the road, so it under-counts by 271. At a true 70 mph the first turns 675 times a minute, the second 657.