Tire RulerWhat changes when you switch to 255/70R17
- Height: +0.55″ (+1.8%), so ground clearance at the axle goes up 0.28″.
- Width: +0.39″ (10 mm). Check inner clearance to the suspension and frame, and the fender liner at full lock.
- Sidewall: +0.28″. A taller sidewall rides a bit softer and protects the wheel off-road.
- Revolutions per mile: 661 → 649. Your gears act about 1.8% taller; at 65 mph in a 0.69 top gear with 3.73s, that’s 1,843 → 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 255/70R17 than 245/70R17?
255/70R17 is 0.55 inches (1.8%) taller and 0.39 inches wider: 31.1" × 10.0" versus 30.5" × 9.6".
Will 255/70R17 change my speedometer?
Yes, by 1.8%. Going from 245/70R17 to 255/70R17, an indicated 60 mph is about 61.1 mph.
Can I replace 245/70R17 with 255/70R17?
Often, yes: the height difference is within the ±3% most tire shops accept. Both fit a 17" wheel; confirm the rim width, load index and clearance for your vehicle.
Do I need to regear going from 245/70R17 to 255/70R17?
Usually not for a 1.8% change. With 3.73 gears, the 255/70R17 acts like 3.66.