Tire RulerWhat changes when you switch to 275/70R18
- Height: +0.16″ (+0.5%), so ground clearance at the axle goes up 0.08″.
- Width: −1.67″ (-42 mm). Check inner clearance to the suspension and frame, and the fender liner at full lock.
- Sidewall: +0.08″. A taller sidewall rides a bit softer and protects the wheel off-road.
- Revolutions per mile: 611 → 608. Your gears act about 0.5% taller; at 65 mph in a 0.69 top gear with 3.73s, that’s 1,704 → 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 33x12.50R18?
275/70R18 is 0.16 inches (0.5%) taller and 1.67 inches narrower: 33.2" × 10.8" versus 33.0" × 12.5".
Will 275/70R18 change my speedometer?
Yes, by 0.5%. Going from 33x12.50R18 to 275/70R18, an indicated 60 mph is about 60.3 mph.
Can I replace 33x12.50R18 with 275/70R18?
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 33x12.50R18 to 275/70R18?
Usually not for a 0.5% change. With 3.73 gears, the 275/70R18 acts like 3.71.