265/70R17 vs 285/70R17
Switching from 265/70R17 to 285/70R17 changes the overall diameter by +28.0 mm (+3.5%) — outside the commonly used ±3% guideline. Every figure below is calculated from the two size codes with the standard formulas.
| Measurement | 265/70R17 | 285/70R17 | Difference |
|---|---|---|---|
| Overall diameter | 802.8 mm | 830.8 mm | +28.0 mm (+3.5%) |
| Overall diameter | 31.61 in | 32.71 in | +1.10 in |
| Tire width | 265 mm (10.43 in) | 285 mm (11.22 in) | +20 mm |
| Sidewall height | 185.5 mm (7.30 in) | 199.5 mm (7.85 in) | +14.0 mm |
| Wheel (rim) diameter | 17.0 in | 17.0 in | 0.0 in |
| Circumference | 2522 mm | 2610 mm | +88 mm |
| Revolutions per mile | 2005 | 1937 | -68 |
| Revolutions per km | 396 | 383 | -13 |
Speedometer error
Calibrated for 265/70R17, the speedometer under-reads or over-reads once 285/70R17 is fitted. This is your real speed at each indicated speed:
| Speedometer shows | Actual speed on 285/70R17 | Error |
|---|---|---|
| 20 mph | 20.7 mph | +0.7 mph |
| 40 mph | 41.4 mph | +1.4 mph |
| 60 mph | 62.1 mph | +2.1 mph |
| 80 mph | 82.8 mph | +2.8 mph |
| 100 mph | 103.5 mph | +3.5 mph |
How these two sizes are worked out
265/70R17 breaks down as a 265 mm tread width with a sidewall of 70% of that width (185.5 mm) on a 17.0-inch wheel, giving an overall diameter of 802.8 mm (31.61 in). 285/70R17 works out to 830.8 mm (32.71 in) the same way. The standard formulas are the same ones used on the tire size calculator page: diameter = rim × 25.4 + 2 × sidewall, circumference = π × diameter, revolutions per mile = 63,360 ÷ diameter in inches.
Nominal sizes vary slightly between brands and models, and tread wear shrinks a tire over its life. These figures follow the size codes exactly; your vehicle manual or a professional tire shop is the authority for what fits your vehicle.
More comparisons
Frequently asked questions
Can I replace 265/70R17 tires with 285/70R17?
The diameter change is +3.5%, which is outside the commonly used ±3% guideline. Diameter is only one part of fitment — wheel width range, load index, speed rating and physical clearance all have to check out too, so confirm with your vehicle manual or a professional tire shop before buying.
Will 285/70R17 make my speedometer read wrong?
Yes, by the diameter ratio. When the dial shows 60 mph you are really doing 62.1 mph on 285/70R17. The full table above covers 20 to 100 mph.
Which tire is taller, 265/70R17 or 285/70R17?
285/70R17 is taller — 830.8 mm against 802.8 mm overall diameter, a difference of 28.0 mm.