275/65R18 vs 285/65R18 — the step you take to change nothing
What an owner picks when the objective is a different tire rather than a different size.
285/65R18 is 0.51 in taller than 275/65R18 (1.60%) and 0.39 in wider. A speedometer calibrated for 275/65R18 would under-read by 1.60%.
Measured against each other
Overall diameter
32.07 in32.59 in+0.51 in (+1.60%)Section width
10.83 in / 275 mm11.22 in / 285 mm+0.39 in (+3.64%)Sidewall height
7.04 in7.29 in+0.26 inCircumference
100.8 in102.4 in+1.6 inRevolutions per mile
628.8618.9-9.9Ride height at the axle
——+0.26 inSpeedometer reading
——+1.60% under-read
| Dimension | 275/65R18 | 285/65R18 | Change |
|---|---|---|---|
| Overall diameter | 32.07 in | 32.59 in | +0.51 in (+1.60%) |
| Section width | 10.83 in / 275 mm | 11.22 in / 285 mm | +0.39 in (+3.64%) |
| Sidewall height | 7.04 in | 7.29 in | +0.26 in |
| Circumference | 100.8 in | 102.4 in | +1.6 in |
| Revolutions per mile | 628.8 | 618.9 | -9.9 |
| Ride height at the axle | — | — | +0.26 in |
| Speedometer reading | — | — | +1.60% under-read |
Calibrated for 275/65R18, running 285/65R18
- Dial reads 30
- 30.5 mph
- Dial reads 50
- 50.8 mph
- Dial reads 70
- 71.1 mph
- Odometer counts 100
- 101.6 mi covered
Change either size in the comparison tool, or see the full speed table in the speedometer error calculator.
Sometimes the point of a size change is that there is no size change worth mentioning. This is that pairing.
1.60%, in context
A set of tires worn from new to their wear indicators loses roughly a third of an inch of diameter — around two-thirds of what this swap adds. So the change is smaller than something every vehicle already does to itself between tire purchases, and it happens in the opposite direction.
The needle runs about a mile an hour light at motorway pace. That is the entire list.
The dimensions
Section width rises 0.39 in, from 10.83 in to 11.22 in — 3.64%. Sidewall rises 0.26 in, because 65% of a wider casing is taller, and since the wheel is unchanged the axle gains the same quarter inch.
There is no meaningful new demand on space in any direction.
What the owner is actually buying
Availability, usually. 285/65R18 is more heavily represented in all-terrain and rugged patterns than
275/65R18, and it is more commonly offered in LT construction with the higher load ratings that
implies. An owner who wants a specific tire often finds it exists in the 285 and not in the 275, and
takes the half inch as a consequence rather than a goal.
Appearance plays a part too — 0.39 in of extra casing fills an 18-inch arch slightly better — but it is a subtle difference at this magnitude.
No calibration consequence at all
The reason this pairing is worth publishing is precisely that it has no consequences. There is no speedometer allowance to make, no odometer correction to apply, no gearing arithmetic to perform, and nothing new for the tire to clear. The vehicle behaves as though nothing happened, because as far as anything that counts wheel revolutions is concerned, very nearly nothing did.
That is a legitimate answer to a legitimate question, and it is the answer most people looking up this pair are hoping for.
Where the bigger steps are
On the same wheel, 285/75R18 reaches 34.83 in and is a genuine project. Off the wheel entirely, 285/65R20 and 35x12.50R20 both change the wheel and the tire together. This page is the option that changes neither in any way the truck will notice.