215/75R18 vs 235/65R18
Going from one to the other changes the overall height by -2.2 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 215/75R18 | 235/65R18 | Change |
|---|---|---|---|
| Overall height | 30.7" | 30.0" | -2.2 % |
| Sidewall | 6.35" | 6.01" | -5.3 % |
| Section width | 215 mm | 235 mm | +9.3 % |
| Circumference | 96.4" | 94.3" | -2.2 % |
| Revs per mile | 657 | 672 | +2.2 % |
| Axle height | 15.35" | 15.01" | -8.5 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 215/75R18. Fit 235/65R18 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.3 mph | -0.7 |
| 50 mph | 48.9 mph | -1.1 |
| 70 mph | 68.5 mph | -1.5 |
| 90 mph | 88.0 mph | -2.0 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,782 on the road, so it over-counts by 218. At a true 70 mph the first turns 767 times a minute, the second 784.
What drivers reported
Nobody has filed a complaint naming 215/75R18. 235/65R18 carries 10.