215/35R18 vs 235/35R18
Going from one to the other changes the overall height by +2.3 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 215/35R18 | 235/35R18 | Change |
|---|---|---|---|
| Overall height | 23.9" | 24.5" | +2.3 % |
| Sidewall | 2.96" | 3.24" | +9.3 % |
| Section width | 215 mm | 235 mm | +9.3 % |
| Circumference | 75.2" | 76.9" | +2.3 % |
| Revs per mile | 843 | 824 | -2.3 % |
| Axle height | 11.96" | 12.24" | +7.0 mm |
| Approved rim width | 6–8" | 6.5–8.5" | overlap 6.5–8" |
Both are approved on a rim 6.5" to 8" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 215/35R18. Fit 235/35R18 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.7 mph | +0.7 |
| 50 mph | 51.2 mph | +1.2 |
| 70 mph | 71.6 mph | +1.6 |
| 90 mph | 92.1 mph | +2.1 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,230 on the road, so it under-counts by 230. At a true 70 mph the first turns 983 times a minute, the second 961.
What drivers reported
215/35R18 carries 2 complaints. Nobody has filed one naming 235/35R18.