335/50R21 vs 355/45R21
Going from one to the other changes the overall height by -1.8 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 335/50R21 | 355/45R21 | Change |
|---|---|---|---|
| Overall height | 34.2" | 33.6" | -1.8 % |
| Sidewall | 6.59" | 6.29" | -4.6 % |
| Section width | 335 mm | 355 mm | +6.0 % |
| Circumference | 107.4" | 105.5" | -1.8 % |
| Revs per mile | 590 | 601 | +1.8 % |
| Axle height | 17.09" | 16.79" | -7.8 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 335/50R21. Fit 355/45R21 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.5 mph | -0.5 |
| 50 mph | 49.1 mph | -0.9 |
| 70 mph | 68.8 mph | -1.2 |
| 90 mph | 88.4 mph | -1.6 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,822 on the road, so it over-counts by 178. At a true 70 mph the first turns 688 times a minute, the second 701.