285/65R18 is 0.6″ taller than 275/65R18 on average, going by the heights their makers list (32.1″ vs 32.7″). On paper the gap is 0.51″.
Going from 275/65R18 to 285/65R18.
Lift is half the height difference, since the axle sits at the middle of the tire. The speedometer figure assumes it was set for 275/65R18 and uses the revolutions per mile the makers publish: at an indicated 60 mph you'd be doing 60.9 mph.
| 275/65R18 | 285/65R18 | Difference | |
|---|---|---|---|
| Listed height ″ | 32.09–32.44 | 32.56–33.40 | +0.59 |
| Size code height ″ | 32.07 | 32.59 | +0.51 |
| Height under load ″ | 31.2 | 31.6 | +0.5 |
| Width ″ | 10.83 | 11.22 | +0.39 |
| Listed width ″ | 10.7–11.0 | 10.9–11.5 | +0.5 |
| Sidewall ″ | 7.04 | 7.29 | +0.26 |
| Wheel ″ | 18 | 18 | same |
| Weight lb | 37.7–63.0 | 41.1–66.8 | +10.0 |
| Tread depth /32″ | 10–19 | 13–19 | +2.2 |
| Tires listed | 46 | 15 |
The same model in each size, by the heights the maker lists. Averages where a model comes in several load ranges.
| Tire | 275/65R18 ″ | 285/65R18 ″ | Taller by | Heavier by |
|---|---|---|---|---|
| BFGoodrich All-Terrain T/A KO3 | 32.10 | 32.60 | +0.50″ | +2.2 lb |
| BFGoodrich HD-Terrain T/A KT | 32.10 | 32.60 | +0.50″ | +4.0 lb |
| BFGoodrich Mud-Terrain T/A KM3 | 32.10 | 32.60 | +0.50″ | +2.8 lb |
| General Grabber A/TX | 32.10 | 32.60 | +0.50″ | +5.4 lb |
| Michelin Defender LTX M/S 2 | 32.10 | 32.60 | +0.50″ | +2.1 lb |
| Mickey Thompson Baja Boss A/T | 32.40 | 33.20 | +0.80″ | +18.0 lb |
| Mickey Thompson Baja Legend EXP | 32.30 | 33.00 | +0.70″ | +5.0 lb |
| Toyo Open Country A/T III | 32.18 | 32.56 | +0.38″ | +5.8 lb |
| Toyo Open Country M/T | 32.32 | 32.80 | +0.47″ | +4.2 lb |
| Toyo Open Country R/T Pro | 32.10 | 32.60 | +0.50″ | +3.6 lb |
| Toyo Open Country R/T Trail | 32.09 | 32.56 | +0.47″ | +13.9 lb |
0.59″ on average, going by the heights tire makers list: 275/65R18 tires are listed at 32.09–32.44″ and 285/65R18 at 32.56–33.40″. The size codes work out to 32.07″ and 32.59″, a 0.51″ difference.
The tire's radius grows by 0.30″, so the axle sits about 0.30″ higher, and the top of the tread comes 0.30″ closer to the fender. 285/65R18 is also 0.39″ wider on paper, 0.20″ per side on the same wheel. Whether it fits depends on your vehicle, lift and wheel offset.
Yes. If it's set for 275/65R18, it will read about 1.5% slow: at an indicated 60 mph you'll be doing 60.9 mph. Worked out from the revolutions per mile the makers publish.
Both fit a 18-inch wheel. Wheel widths approved for both run from 8.0″ to 9.5″.