205/45R18 vs 215/45R18
Going from one to the other changes the overall height by +1.4 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 205/45R18 | 215/45R18 | Change |
|---|---|---|---|
| Overall height | 25.3" | 25.6" | +1.4 % |
| Sidewall | 3.63" | 3.81" | +4.9 % |
| Section width | 205 mm | 215 mm | +4.9 % |
| Circumference | 79.4" | 80.5" | +1.4 % |
| Revs per mile | 798 | 787 | -1.4 % |
| Axle height | 12.63" | 12.81" | +4.5 mm |
| Approved rim width | 5.5–7.5" | 6–8" | 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 205/45R18. Fit 215/45R18 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.4 mph | +0.4 |
| 50 mph | 50.7 mph | +0.7 |
| 70 mph | 71.0 mph | +1.0 |
| 90 mph | 91.3 mph | +1.3 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,140 on the road, so it under-counts by 140. At a true 70 mph the first turns 931 times a minute, the second 918.
What drivers reported
Nobody has filed a complaint naming 205/45R18. 215/45R18 carries 5.