205/40R20 vs 225/35R20
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 | 205/40R20 | 225/35R20 | Change |
|---|---|---|---|
| Overall height | 26.5" | 26.2" | -1.0 % |
| Sidewall | 3.23" | 3.10" | -4.0 % |
| Section width | 205 mm | 225 mm | +9.8 % |
| Circumference | 83.1" | 82.3" | -1.0 % |
| Revs per mile | 762 | 770 | +1.0 % |
| Axle height | 13.23" | 13.10" | -3.3 mm |
| Approved rim width | 5.5–7.5" | 6–8.5" | overlap 6–7.5" |
Both are approved on a rim 6" to 7.5" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 205/40R20. Fit 225/35R20 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.7 mph | -0.3 |
| 50 mph | 49.5 mph | -0.5 |
| 70 mph | 69.3 mph | -0.7 |
| 90 mph | 89.1 mph | -0.9 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,903 on the road, so it over-counts by 97. At a true 70 mph the first turns 889 times a minute, the second 898.
What drivers reported
Nobody has filed a complaint naming 205/40R20. 225/35R20 carries 2.