335/30R20 vs 315/35R20
Going from one to the other changes the overall height by +2.8 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 335/30R20 | 315/35R20 | Change |
|---|---|---|---|
| Overall height | 27.9" | 28.7" | +2.8 % |
| Sidewall | 3.96" | 4.34" | +9.7 % |
| Section width | 335 mm | 315 mm | -6.0 % |
| Circumference | 87.7" | 90.1" | +2.8 % |
| Revs per mile | 723 | 703 | -2.8 % |
| Axle height | 13.96" | 14.34" | +9.8 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 335/30R20. Fit 315/35R20 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 | 92.5 mph | +2.5 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,275 on the road, so it under-counts by 275. At a true 70 mph the first turns 843 times a minute, the second 820.
What drivers reported
Nobody has filed a complaint naming 335/30R20. 315/35R20 carries 2.