Tire RulerWhat changes when you switch to 255/70R18
- Height: +0.49″ (+1.6%), so ground clearance at the axle goes up 0.25″.
- Width: −0.39″ (-10 mm). Check inner clearance to the suspension and frame, and the fender liner at full lock.
- Sidewall: +0.25″. A taller sidewall rides a bit softer and protects the wheel off-road.
- Revolutions per mile: 639 → 629. Your gears act about 1.6% taller; at 65 mph in a 0.69 top gear with 3.73s, that’s 1,782 → 1,754 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 255/70R18 than 265/65R18?
255/70R18 is 0.49 inches (1.6%) taller and 0.39 inches narrower: 32.1" × 10.0" versus 31.6" × 10.4".
Will 255/70R18 change my speedometer?
Yes, by 1.6%. Going from 265/65R18 to 255/70R18, an indicated 60 mph is about 60.9 mph.
Can I replace 265/65R18 with 255/70R18?
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 265/65R18 to 255/70R18?
Usually not for a 1.6% change. With 3.73 gears, the 255/70R18 acts like 3.67.