255/45R21 vs 265/45R21
Going from one to the other changes the overall height by +1.2 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 255/45R21 | 265/45R21 | Change |
|---|---|---|---|
| Overall height | 30.0" | 30.4" | +1.2 % |
| Sidewall | 4.52" | 4.69" | +3.9 % |
| Section width | 255 mm | 265 mm | +3.9 % |
| Circumference | 94.4" | 95.5" | +1.2 % |
| Revs per mile | 671 | 664 | -1.2 % |
| Axle height | 15.02" | 15.19" | +4.5 mm |
| Approved rim width | 7–9.5" | 7.5–9.5" | overlap 7.5–9.5" |
Both are approved on a rim 7.5" to 9.5" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 255/45R21. Fit 265/45R21 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.4 mph | +0.4 |
| 50 mph | 50.6 mph | +0.6 |
| 70 mph | 70.8 mph | +0.8 |
| 90 mph | 91.1 mph | +1.1 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,118 on the road, so it under-counts by 118. At a true 70 mph the first turns 783 times a minute, the second 774.
What drivers reported
Nobody has filed a complaint naming 255/45R21. 265/45R21 carries 2.