Tire RulerWhat changes when you switch to 285/70R17
- Height: +0.65″ (+2.0%), so ground clearance at the axle goes up 0.32″.
- Width: +1.18″ (30 mm). Check inner clearance to the suspension and frame, and the fender liner at full lock.
- Sidewall: +0.32″. A taller sidewall rides a bit softer and protects the wheel off-road.
- Revolutions per mile: 629 → 617. Your gears act about 2.0% taller; at 65 mph in a 0.69 top gear with 3.73s, that’s 1,754 → 1,719 RPM.
Sizes are theoretical, from the sidewall code. The same size can differ by a few tenths of an inch between brands and tread patterns; check the maker’s spec sheet for the exact model.
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Frequently asked questions
How much bigger is 285/70R17 than 255/75R17?
285/70R17 is 0.65 inches (2.0%) taller and 1.18 inches wider: 32.7" × 11.2" versus 32.1" × 10.0".
Will 285/70R17 change my speedometer?
Yes, by 2.0%. Going from 255/75R17 to 285/70R17, an indicated 60 mph is about 61.2 mph.
Can I replace 255/75R17 with 285/70R17?
Often, yes: the height difference is within the ±3% most tire shops accept. Both fit a 17" wheel; confirm the rim width, load index and clearance for your vehicle.
Do I need to regear going from 255/75R17 to 285/70R17?
Usually not for a 2.0% change. With 3.73 gears, the 285/70R17 acts like 3.66.