Tire RulerWhat changes when you switch to 285/60R20
- Height: +0.26″ (+0.8%), so ground clearance at the axle goes up 0.13″.
- Width: −0.79″ (-20 mm). Check inner clearance to the suspension and frame, and the fender liner at full lock.
- Sidewall: +0.13″. A taller sidewall rides a bit softer and protects the wheel off-road.
- Revolutions per mile: 607 → 603. Your gears act about 0.8% taller; at 65 mph in a 0.69 top gear with 3.73s, that’s 1,693 → 1,680 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 285/60R20 than 305/55R20?
285/60R20 is 0.26 inches (0.8%) taller and 0.79 inches narrower: 33.5" × 11.2" versus 33.2" × 12.0".
Will 285/60R20 change my speedometer?
Yes, by 0.8%. Going from 305/55R20 to 285/60R20, an indicated 60 mph is about 60.5 mph.
Can I replace 305/55R20 with 285/60R20?
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 305/55R20 to 285/60R20?
Usually not for a 0.8% change. With 3.73 gears, the 285/60R20 acts like 3.70.