265/70R17 vs 285/70R17: Size, Clearance and Speedometer Differences

In the 265/70R17 vs 285/70R17 matchup, the 285 is 1.10 in taller and 0.79 in wider than the 265. That buys you about 0.55 in more ground clearance and a 3.49% speedometer error. At an indicated 60 mph on 285s, in a truck calibrated for 265s, you are actually rolling 62.1 mph.

What are the exact numbers for each size?

Here is the side by side. Same 17 in rim, different everything else.

• 265/70R17: 31.61 in diameter, 10.43 in section width, 7.30 in sidewall, 638 revolutions per mile.
• 285/70R17: 32.71 in diameter, 11.22 in section width, 7.85 in sidewall, 617 revolutions per mile.
• Difference: the 285 is 1.10 in taller, 0.79 in wider, and carries 0.55 in more sidewall.
• Revolutions per mile: 638 vs 617. The bigger tire turns fewer times to cover the same mile.

Those revolution counts are the whole story behind the speedometer problem. Your truck counts rotations. It does not measure the road. Fewer rotations per mile means the computer thinks you have gone less distance than you really have. Want to run your own pairing? Use the Tire Size Calculator.

Is a 285 taller than a 265 if both are 70 series?

Yes, and this trips up a lot of people. Both sizes say 70. Most folks read that as the same sidewall height. It is not. The aspect ratio is a percentage, not a fixed measure in inches.

The 70 means the sidewall is 70% of the section width. On a 265, 70% of 265 mm gives you a 7.30 in sidewall. On a 285, 70% of a bigger number gives you a 7.85 in sidewall. Wider tire, same percentage, taller sidewall. That is 0.55 in of extra rubber on each side.

Now stack it up. You have 0.55 in of extra sidewall on top and 0.55 in on the bottom. Add them and you get the 1.10 in diameter increase. The rim stayed 17 in the whole time. All the growth came from the sidewall math. If the numbering system still feels like a code, start with how to read tire size and it will click.

How much clearance do you actually gain?

Half of what you think. The 285 is 1.10 in taller in diameter, but your ground clearance only goes up 0.55 in.

Here is why. Diameter is the full height of the tire, top to bottom. Your axle sits at the center. When the tire grows 1.10 in in diameter, the center only rises by the radius change, which is 0.55 in. The other 0.55 in went upward into the wheel well, where it does nothing for you except get closer to the fender liner.

So the honest way to say it: 1.10 in of tire buys 0.55 in of clearance. If you were hoping to clear a specific rock or a specific curb, plan around 0.55 in, not 1.10 in.

How much wider is a 285 than a 265?

The 285 is 0.79 in wider in section width, 11.22 in versus 10.43 in. That is measured at the widest point of the tire, sidewall bulge included, not the tread you can see on the ground.

That extra width is where most of the fitment trouble lives. The tire does not just sit there. It turns. It compresses. It moves through the wheel well as the suspension cycles. Three quarters of an inch of extra width has to live somewhere at full lock, and the upper control arm, the sway bar end link and the fender liner all get a vote.

Will 285s fit where 265s did?

Maybe. Nobody can promise you a yes from a size chart alone. Both tires mount on a 17 in rim, so the wheel diameter is a non issue. Everything else is open.

What actually decides it:

• Rim width: a wider tire needs an approved rim width range. Squeezing an 11.22 in tire onto a narrow wheel changes the profile and the way it sits.
• Offset and backspacing: this decides whether the extra width pushes inboard toward suspension parts or outboard toward the fender.
• Suspension and trim: two trucks with the same badge can have different ride heights, different arms and different liners.
• Turning at full lock: plenty of setups clear fine going straight and rub hard in a parking lot.

Check the door placard for what your vehicle was built with. Then confirm with a tire professional who can look at your specific rim, offset and suspension. Treat any internet fitment claim, including the general one on this page, as a starting point and not clearance.

What are the real tradeoffs of going wider and taller?

You get a wider contact patch and a more aggressive stance. That is the appeal, and it is a real one. The 285 fills the well better and looks the part. You also get 0.55 in more sidewall to soak up sharp hits.

The costs are just as real. Your speedometer reads low by 3.49%, so you are quietly speeding by roughly 2 mph at highway pace. A bigger tire is also heavier rotating mass, and rotating mass is the mass your engine and brakes fight every time you accelerate or stop.

On fuel economy and tread wear, I will be straight with you. Directionally, a taller and wider tire with more mass tends to cost you some mpg and can change how the tread wears, especially if alignment and inflation are not sorted. I am not going to hand you a number, because the honest number depends on your engine, gearing, tread pattern and right foot. Anyone quoting you an exact mpg penalty for this swap is guessing.

Does the speedometer error matter?

It matters more than people admit. A 3.49% error is small on paper and consistent in practice. Indicated 60 mph is a true 62.1 mph. Scale that up and the gap widens at highway speeds.

It also touches your odometer. Every mile you drive registers as slightly less than a mile. That nudges your service intervals, your trip math and your resale mileage over time. Some trucks can be recalibrated for a new tire size, others need an aftermarket tuner. Worth asking about before you buy. For the full mechanism, read does tire size affect speedometer.

Which one should you buy?

Stay with 265/70R17 if you want a factory calibrated speedometer, the lightest rotating mass of the two, and a fitment you already know works. It is the boring, correct answer for a daily driver truck.

Step up to 285/70R17 if you want the stance, the wider contact patch and the extra 0.55 in under the diff, and you are willing to verify fitment and live with a speedometer that reads low. Neither choice is wrong. They are just different bills.

Bottom line

The 285/70R17 is 1.10 in taller, 0.79 in wider and rides on 0.55 in more sidewall than the 265/70R17. It gains you 0.55 in of ground clearance, not 1.10 in, because the axle only rises by the radius. It drops you from 638 to 617 revolutions per mile, which is where the 3.49% speedometer error comes from. Same 17 in rim, but rim width, offset, suspension and trim decide whether it fits your truck. Check the placard, ask a tire professional, and run the numbers for your own setup with the Tire Size Calculator.