335/45R21 vs 355/45R21
Going from one to the other changes the overall height by +2.2 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 335/45R21 | 355/45R21 | Change |
|---|---|---|---|
| Overall height | 32.9" | 33.6" | +2.2 % |
| Sidewall | 5.94" | 6.29" | +6.0 % |
| Section width | 335 mm | 355 mm | +6.0 % |
| Circumference | 103.3" | 105.5" | +2.2 % |
| Revs per mile | 614 | 601 | -2.2 % |
| Axle height | 16.44" | 16.79" | +9.0 mm |
| Approved rim width | 9.5–12.5" | 10–13" | overlap 10–12.5" |
Both are approved on a rim 10" to 12.5" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 335/45R21. Fit 355/45R21 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.6 mph | +0.6 |
| 50 mph | 51.1 mph | +1.1 |
| 70 mph | 71.5 mph | +1.5 |
| 90 mph | 91.9 mph | +1.9 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,216 on the road, so it under-counts by 216. At a true 70 mph the first turns 716 times a minute, the second 701.