Tire RulerWhat changes when you switch to 245/70R17
- Height: +0.45″ (+1.5%), so ground clearance at the axle goes up 0.23″.
- Width: −0.39″ (-10 mm). Check inner clearance to the suspension and frame, and the fender liner at full lock.
- Sidewall: +0.23″. A taller sidewall rides a bit softer and protects the wheel off-road.
- Revolutions per mile: 671 → 661. Your gears act about 1.5% taller; at 65 mph in a 0.69 top gear with 3.73s, that’s 1,871 → 1,843 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 245/70R17 than 255/65R17?
245/70R17 is 0.45 inches (1.5%) taller and 0.39 inches narrower: 30.5" × 9.6" versus 30.1" × 10.0".
Will 245/70R17 change my speedometer?
Yes, by 1.5%. Going from 255/65R17 to 245/70R17, an indicated 60 mph is about 60.9 mph.
Can I replace 255/65R17 with 245/70R17?
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 255/65R17 to 245/70R17?
Usually not for a 1.5% change. With 3.73 gears, the 245/70R17 acts like 3.67.