Tire RulerWhat changes when you switch to 275/70R18
- Height: +1.10″ (+3.4%), so ground clearance at the axle goes up 0.55″.
- Width: +0.79″ (20 mm). Check inner clearance to the suspension and frame, and the fender liner at full lock.
- Sidewall: +0.55″. A taller sidewall rides a bit softer and protects the wheel off-road.
- Revolutions per mile: 629 → 608. Your gears act about 3.4% taller; at 65 mph in a 0.69 top gear with 3.73s, that’s 1,754 → 1,696 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 275/70R18 than 255/70R18?
275/70R18 is 1.10 inches (3.4%) taller and 0.79 inches wider: 33.2" × 10.8" versus 32.1" × 10.0".
Will 275/70R18 change my speedometer?
Yes, by 3.4%. Going from 255/70R18 to 275/70R18, an indicated 60 mph is about 62.1 mph.
Can I replace 255/70R18 with 275/70R18?
Possibly, but the height difference is over 3%, so check clearance and plan to recalibrate the speedometer. 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 275/70R18?
Usually not for a 3.4% change. With 3.73 gears, the 275/70R18 acts like 3.61.