355/60R21 vs 335/65R21
Going from one to the other changes the overall height by +1.0 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 355/60R21 | 335/65R21 | Change |
|---|---|---|---|
| Overall height | 37.8" | 38.1" | +1.0 % |
| Sidewall | 8.39" | 8.57" | +2.2 % |
| Section width | 355 mm | 335 mm | -5.6 % |
| Circumference | 118.7" | 119.8" | +1.0 % |
| Revs per mile | 534 | 529 | -1.0 % |
| Axle height | 18.89" | 19.07" | +4.8 mm |
| Approved rim width | 10–13" | 9.5–12.5" | 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 355/60R21. Fit 335/65R21 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.3 mph | +0.3 |
| 50 mph | 50.5 mph | +0.5 |
| 70 mph | 70.7 mph | +0.7 |
| 90 mph | 90.9 mph | +0.9 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,099 on the road, so it under-counts by 99. At a true 70 mph the first turns 623 times a minute, the second 617.