Tire RulerWhat changes when you switch to 255/55R20
- Height: +0.61″ (+2.0%), so ground clearance at the axle goes up 0.31″.
- Width: −0.39″ (-10 mm). Check inner clearance to the suspension and frame, and the fender liner at full lock.
- Sidewall: +0.31″. A taller sidewall rides a bit softer and protects the wheel off-road.
- Revolutions per mile: 663 → 650. Your gears act about 2.0% taller; at 65 mph in a 0.69 top gear with 3.73s, that’s 1,848 → 1,811 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 255/55R20 than 265/50R20?
255/55R20 is 0.61 inches (2.0%) taller and 0.39 inches narrower: 31.0" × 10.0" versus 30.4" × 10.4".
Will 255/55R20 change my speedometer?
Yes, by 2.0%. Going from 265/50R20 to 255/55R20, an indicated 60 mph is about 61.2 mph.
Can I replace 265/50R20 with 255/55R20?
Often, yes: the height difference is within the ±3% most tire shops accept. Both fit a 20" wheel; confirm the rim width, load index and clearance for your vehicle.
Do I need to regear going from 265/50R20 to 255/55R20?
Usually not for a 2.0% change. With 3.73 gears, the 255/55R20 acts like 3.66.