245/80R18 vs 265/70R18
Going from one to the other changes the overall height by -2.5 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 245/80R18 | 265/70R18 | Change |
|---|---|---|---|
| Overall height | 33.4" | 32.6" | -2.5 % |
| Sidewall | 7.72" | 7.30" | -5.4 % |
| Section width | 245 mm | 265 mm | +8.2 % |
| Circumference | 105.0" | 102.4" | -2.5 % |
| Revs per mile | 603 | 619 | +2.5 % |
| Axle height | 16.72" | 16.30" | -10.5 mm |
| Approved rim width | 7–9" | 7.5–9.5" | overlap 7.5–9" |
Both are approved on a rim 7.5" to 9" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 245/80R18. Fit 265/70R18 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.3 mph | -0.7 |
| 50 mph | 48.8 mph | -1.2 |
| 70 mph | 68.3 mph | -1.7 |
| 90 mph | 87.8 mph | -2.2 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,753 on the road, so it over-counts by 247. At a true 70 mph the first turns 704 times a minute, the second 722.
What drivers reported
Nobody has filed a complaint naming 245/80R18. 265/70R18 carries 20.