285/40R21 vs 295/35R21
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 | 285/40R21 | 295/35R21 | Change |
|---|---|---|---|
| Overall height | 30.0" | 29.1" | -2.8 % |
| Sidewall | 4.49" | 4.06" | -9.4 % |
| Section width | 285 mm | 295 mm | +3.5 % |
| Circumference | 94.2" | 91.5" | -2.8 % |
| Revs per mile | 673 | 692 | +2.8 % |
| Axle height | 14.99" | 14.56" | -10.8 mm |
| Approved rim width | 8–10.5" | 8.5–11" | overlap 8.5–10.5" |
Both are approved on a rim 8.5" to 10.5" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 285/40R21. Fit 295/35R21 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.2 mph | -0.8 |
| 50 mph | 48.6 mph | -1.4 |
| 70 mph | 68.0 mph | -2.0 |
| 90 mph | 87.5 mph | -2.5 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,718 on the road, so it over-counts by 282. At a true 70 mph the first turns 785 times a minute, the second 808.
What drivers reported
Nobody has filed a complaint naming 285/40R21. 295/35R21 carries 1.