A 285 tire is not always 33 inches tall; its full height changes with the sidewall ratio and wheel diameter.
No. A 285 tells you the tire’s width in millimeters, not its full height. That’s why one 285 can sit close to 33 inches, while another can land under 32 or climb past 33.5.
The size that truck owners mention most is 285/70R17. That one works out to about 32.7 inches, so many shops and forum threads lump it into the “33-inch tire” bucket. That shorthand is fine for casual talk, but it’s loose math.
If you’re shopping, checking clearance, or trying to keep the speedometer close, don’t stop at “285.” You need the full size stamp on the sidewall. One missing number can change the answer by more than an inch.
Is A 285 A 33 Inch Tire? Here’s When It Is
A metric tire size gives you three pieces of information. Once you read all three, the answer gets simple.
- 285 = section width in millimeters.
- 70 in 285/70R17 = sidewall height as a percentage of that width.
- 17 = wheel diameter in inches.
So a 285 on its own is never enough to call a tire a 33. The sidewall ratio does the heavy lifting. A taller sidewall pushes the tire upward. A shorter sidewall pulls it down.
Reading A 285 Tire Size Without Guesswork
The math is plain once you break it into pieces. Take 285/70R17. First, 70 percent of 285 mm gives you one sidewall. Then double that, since the tire has a sidewall above the wheel and one below it. After that, add the 17-inch wheel.
- Find the sidewall height: 285 × 0.70 = 199.5 mm.
- Convert sidewall height to inches: 199.5 ÷ 25.4 = 7.85 inches.
- Double the sidewall: 7.85 × 2 = 15.7 inches.
- Add the wheel: 15.7 + 17 = 32.7 inches.
That same layout applies to every other 285 size. If the middle number changes from 70 to 75, the tire gets taller. If the wheel jumps from 17 to 18 or 20, the final height shifts again. Bridgestone’s tire size explainer lays out the same width, aspect ratio, and rim-diameter structure you see on the sidewall.
There’s one more wrinkle. Published tire math gives you a nominal height, not a promise carved in stone. Brand-to-brand specs can move a bit, and wheel width can nudge the mounted shape too. That won’t turn a 31-inch tire into a 33, but it can matter when your truck already sits tight to the fender liner or upper control arm.
| 285 Tire Size | Calculated Diameter | 33-Inch Verdict |
|---|---|---|
| 285/50R20 | 31.2 inches | No |
| 285/55R18 | 30.3 inches | No |
| 285/65R17 | 31.6 inches | No |
| 285/70R16 | 31.7 inches | No |
| 285/60R18 | 31.5 inches | No |
| 285/45R22 | 32.1 inches | Close, but under |
| 285/55R20 | 32.3 inches | Close, but under |
| 285/65R18 | 32.6 inches | Close, but under |
| 285/70R17 | 32.7 inches | Commonly treated as 33 |
| 285/75R16 | 32.8 inches | Commonly treated as 33 |
| 285/60R20 | 33.5 inches | Over 33 |
| 285/70R18 | 33.7 inches | Over 33 |
| 285/75R17 | 33.8 inches | Over 33 |
Which 285 Sizes Sit Near 33 Inches
The two sizes people usually mean when they say “285s are 33s” are 285/70R17 and 285/75R16. Both land just under 33 inches on paper. In day-to-day truck talk, that’s close enough that many owners round up and move on.
That shortcut can trip you up when you’re comparing lift kits, spare-tire storage, or gearing changes. A 285/75R17 is not playing in the same space as a 285/70R17. One is about 33.8 inches. The other is about 32.7. That gap is larger than it sounds when the truck is at full lock or full compression.
If you’re cross-shopping wheels, keep the whole package in view. A tire that is “close to a 33” by diameter can still be wide enough to rub in spots that a narrower true 33 would miss. Width and height get bundled together in tire talk, but the truck feels each one in a different place.
Fitment Checks Before You Buy Any 285
Before you swap from stock, check the door placard, your owner’s manual, and the tire’s load rating. The NHTSA tire safety brochure says replacement tires should be the same size as the original tire or another size the vehicle maker recommends. That matters more than shop slang like “31s,” “33s,” or “35s.”
Clearance And Rubbing
Diameter is only part of the fitment story. A 285 can touch the fender liner, mud flap, sway bar, frame, or upper control arm before height becomes the issue. Wheel offset, wheel width, suspension height, and alignment all change the result.
If you’re close on space, measure at full steering lock and with the suspension compressed. A tire that clears in the driveway can still kiss plastic or metal once the truck drops into a rut or a steep driveway.
Speedometer And Gearing
When diameter grows, the truck travels farther with each rotation. That means the speedometer can read a bit low, and the gearing can feel a touch taller. A jump from a stock size to a near-33 may be small enough for some owners to ignore, but it still changes what the truck is doing.
Load Rating And Placard Match
Don’t chase diameter and forget the load index. The sidewall still has to carry the vehicle, passengers, cargo, and any trailer tongue weight that lands on the rear axle. A size that looks right can still be the wrong pick if the load rating misses the mark.
A Better Shopping Habit
Ask for the full tire size, the load index, and the measured specs sheet from the brand you want. That gives you a clean apples-to-apples comparison. It also cuts out the fog that comes with nicknames like “metric 33” or “roughly 33.”
| What To Check | Why It Matters | What You Want To See |
|---|---|---|
| Full sidewall size | Width alone can’t tell you height | 285/70R17, not just 285 |
| Measured tire specs | Brand specs can shift a bit | Listed overall diameter and section width |
| Door placard and manual | Shows factory-approved sizing and pressure | A size and load range your vehicle can carry |
| Wheel width and offset | Changes inner and outer clearance | A setup known to clear your truck |
| Speedometer change | Taller tires travel farther per rotation | A correction small enough for your goal |
Why Tire Folks Still Call Some 285s 33s
Because rounding is easy. Saying “I run 33s” is faster than saying “I run 285/70R17s that measure about 32.7 inches.” In casual talk, that works. In buying and fitment talk, it can send you down the wrong path.
The clean answer is this: a 285 is a width class, not a finished height. Some 285 sizes sit near 33 inches. Some don’t. If you want the tire that most truck owners mean by a “285 that’s close to a 33,” start with 285/70R17 or 285/75R16, then verify the brand’s measured specs before you order.
References & Sources
- Bridgestone.“How to Read & Determine Tire Size for Your Vehicle”Explains how width, aspect ratio, and rim diameter are read from a metric tire size.
- National Highway Traffic Safety Administration.“Tire Safety”States that replacement tires should match the original size or another size recommended by the vehicle maker.