A 285/75R18 tire measures roughly 34.8 inches tall, one of the more common tall, narrow fitments for 3/4-ton trucks and off-road SUVs.
If you’re shopping for tires or checking clearance on a lift kit, that 34.8-inch figure is the number that matters most. But the “34.8 inches” tells only part of the story. The 285 series width, the 75 aspect ratio that shapes the sidewall, and the 18-inch rim all work together to determine how the tire sits, how it fills the wheel well, and whether it fits your rig.
Here’s what each number in 285/75R18 means, what the tire measures across every dimension, and the fitment details you need before you commit to a set.
What Each Number In 285/75R18 Means
The tire size is metric, and each group of digits plays a specific role.
- 285 is the section width in millimeters, measured from the widest point of the sidewall to the widest point on the other side between the rim lips. That works out to 11.2 inches.
- 75 is the aspect ratio, meaning the sidewall height is 75 percent of the section width. That’s roughly 214 mm, or 8.4 inches of sidewall.
- R stands for radial construction, the standard for passenger and light-truck tires today.
- 18 is the wheel diameter in inches, so this tire fits an 18-inch rim.
Add the 18-inch wheel diameter to twice the 8.4-inch sidewall and you get an overall diameter of 34.8 inches. That’s the number everyone calls “tire height.”
Full Specs: Height, Width, And Circumference
Whether you’re checking clearance against your fenders or adjusting the speedometer after a swap, the full set of dimensions matters, not just the height.
| Dimension | 285/75R18 Value |
|---|---|
| Overall diameter (height) | 34.8 in (885 mm) |
| Section width | 11.2 in (285 mm) |
| Rim diameter | 18 in (457.2 mm) |
| Sidewall height | 8.4 in (214 mm) |
| Circumference | 109.3–109.4 in (2,779 mm) |
| Revolutions per mile | 579–580 |
| Recommended rim width range | 7.5–9.5 in |
That circumference works out to roughly 579 revolutions per mile. If you’re changing from a smaller tire, that’s the figure that throws the speedometer reading off — a 285/75R18 runs about 4 percent larger than a 285/70R18, which measures 33.7 inches tall. That extra 1.1 inches of height translates directly to a slower speedometer and more ground clearance.
Why The Height Varies By Model
The dimensions above are the theoretical values for the size class. Real tires rarely hit those numbers exactly. A load range E tire has a stiffer carcass and often measures right at 34.8 inches unloaded, but the same size in a passenger-rated tire can be slightly shorter or taller depending on how the manufacturer builds it.
Take two popular examples. The Toyo Open Country A/T III in LT285/75R18 lists a 34.8-inch diameter, an 11.3-inch width, and a 7.5–9.5-inch rim range, with a 65-pound weight and a max load of 4,080 pounds at 80 psi. The Goodyear Wrangler DuraTrac RT in the same size also measures 34.8 inches tall but carries a 129/126 load index and a 50,000-mile treadlife warranty. Even at the same nominal height, the two tires have different tread depths, weights, and inflation requirements.
Before you buy, compare the spec sheet of the exact model you’re considering against your truck’s clearance and load needs. A 3.0-inch-taller tire than your current 285/70R18 may contact the fender liner or upper control arm at full compression, especially on a truck without a leveling kit. With the rim width range at 7.5 to 9.5 inches, the tire also needs a wheel that sits within that band to seat correctly.
If you’re weighing options with your truck in mind, our roundup of the best 285/75R18 tire models breaks down which ones fit specific trucks and use cases.
FAQs
Will 285/75R18 tires fit a stock F-150?
That depends on the model year and trim. Many current F-150s come with 18-inch wheels, but the suspension height varies by package. On a stock truck, a 34.8-inch tire often requires trimming or a leveling kit to avoid rubbing at full turn, especially on the front crash bars. Check your specific configuration’s clearance before buying.
What is the difference between 285/75R18 and 285/70R18?
The 75-series has a taller sidewall than the 70-series. The 285/70R18 is 33.7 inches tall, while the 285/75R18 measures 34.8 inches — a difference of about 1.1 inches. The taller tire also has a larger circumference, which means the speedometer reads slightly slower at highway speeds.
Does 285/75R18 use the same rim as 285/70R18?
Yes, both fit an 18-inch wheel, and both accept rim widths between 7.5 and 9.5 inches. The taller 75-series does not require a wider wheel, so if your current 18-inch rims are within that range, they will work for either tire size.
References & Sources
- BFGoodrich Tires. “Browse Tires by Dimension: 285/75R18.” Lists compatible tire models and size specifications.
- TireSize.com. “Toyo Open Country A/T III 285/75R18.” Provides model-specific specs including weight, load, and tread depth.
- TireSize.com. “285/75R18 Tires.” Details mathematical dimensions and circumference values for the size.