Tire RulerWhat changes when you switch to 285/55R20
- Height: +0.43″ (+1.4%), so ground clearance at the axle goes up 0.22″.
- Width: +0.39″ (10 mm). Check inner clearance to the suspension and frame, and the fender liner at full lock.
- Sidewall: +0.22″. A taller sidewall rides a bit softer and protects the wheel off-road.
- Revolutions per mile: 632 → 624. Your gears act about 1.4% taller; at 65 mph in a 0.69 top gear with 3.73s, that’s 1,762 → 1,739 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 285/55R20 than 275/55R20?
285/55R20 is 0.43 inches (1.4%) taller and 0.39 inches wider: 32.3" × 11.2" versus 31.9" × 10.8".
Will 285/55R20 change my speedometer?
Yes, by 1.4%. Going from 275/55R20 to 285/55R20, an indicated 60 mph is about 60.8 mph.
Can I replace 275/55R20 with 285/55R20?
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 275/55R20 to 285/55R20?
Usually not for a 1.4% change. With 3.73 gears, the 285/55R20 acts like 3.68.