Tire RulerWhat changes when you switch to 285/65R18
- Height: +0.53″ (+1.7%), so ground clearance at the axle goes up 0.27″.
- Width: +1.18″ (30 mm). Check inner clearance to the suspension and frame, and the fender liner at full lock.
- Sidewall: +0.27″. A taller sidewall rides a bit softer and protects the wheel off-road.
- Revolutions per mile: 629 → 619. Your gears act about 1.7% taller; at 65 mph in a 0.69 top gear with 3.73s, that’s 1,754 → 1,726 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 285/65R18 than 255/70R18?
285/65R18 is 0.53 inches (1.7%) taller and 1.18 inches wider: 32.6" × 11.2" versus 32.1" × 10.0".
Will 285/65R18 change my speedometer?
Yes, by 1.7%. Going from 255/70R18 to 285/65R18, an indicated 60 mph is about 61.0 mph.
Can I replace 255/70R18 with 285/65R18?
Often, yes: the height difference is within the ±3% most tire shops accept. Both fit an 18" wheel; confirm the rim width, load index and clearance for your vehicle.
Do I need to regear going from 255/70R18 to 285/65R18?
Usually not for a 1.7% change. With 3.73 gears, the 285/65R18 acts like 3.67.