Tire RulerWhat changes when you switch to 255/70R18
- Height: +1.00″ (+3.2%), so ground clearance at the axle goes up 0.50″.
- Width: ±0.00″ (0 mm). A small change; clearance problems are unlikely if the height fits.
- Sidewall: +0.50″. A taller sidewall rides a bit softer and protects the wheel off-road.
- Revolutions per mile: 650 → 629. Your gears act about 3.2% taller; at 65 mph in a 0.69 top gear with 3.73s, that’s 1,811 → 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.
Other comparisons
Frequently asked questions
How much bigger is 255/70R18 than 255/65R18?
255/70R18 is 1.00 inches (3.2%) taller and 0.00 inches wider: 32.1" × 10.0" versus 31.1" × 10.0".
Will 255/70R18 change my speedometer?
Yes, by 3.2%. Going from 255/65R18 to 255/70R18, an indicated 60 mph is about 61.9 mph.
Can I replace 255/65R18 with 255/70R18?
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 255/65R18 to 255/70R18?
Usually not for a 3.2% change. With 3.73 gears, the 255/70R18 acts like 3.61.