Tire Size Box

305/60R17 vs 305/70R17

305/70R17 compared with 305/60R17

+7.6% diameter, 0.0" width

305/70R17 is 33.81" tall vs 31.41". More than the 3% rule of thumb, so check carefully before switching.

31.4"17" rim7.2"12.0" wide
305/60R17 (solid) compared with 305/70R17 (dashed outline), drawn to scale

With 305/70R17 tires, when your speedometer says 60 mph you are really going

64.6 mph

305/70R17 is +2.40 inches (+7.6%) in overall diameter. That is more than the 3% most shops and makers recommend.

305/60R17305/70R17Difference%
Overall diameter31.41"33.81"+2.40"+7.6%
Section width12.01"12.01"0.00"0.0%
Sidewall height7.20"8.41"+1.20"+16.7%
Circumference98.68"106.22"+7.54"+7.6%
Revolutions per mile642.1596.5−45.6−7.1%

Speedometer difference

If your vehicle came with 305/60R17 and you fit 305/70R17, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.5 mph+1.5 mph
30 mph32.3 mph+2.3 mph
40 mph43.1 mph+3.1 mph
50 mph53.8 mph+3.8 mph
60 mph64.6 mph+4.6 mph
65 mph70.0 mph+5.0 mph
70 mph75.4 mph+5.4 mph
75 mph80.7 mph+5.7 mph
80 mph86.1 mph+6.1 mph

Each size on its own

Questions

Which is bigger, 305/60R17 or 305/70R17?
305/70R17 is taller by 2.40 inches (33.81" vs 31.41"). 305/60R17 is the same width.
Can I replace 305/60R17 with 305/70R17?
It is not recommended without checking carefully. The diameter difference is +7.6%, more than the 3% most shops and makers allow. It will throw off the speedometer and may affect ABS, stability control and clearance.
How much will 305/70R17 change my speedometer?
When your speedometer reads 60 mph with 305/70R17 fitted (calibrated for 305/60R17), your real speed is 64.6 mph. Your odometer will under-count miles by about 7.6%.
Will 305/70R17 lift my vehicle?
Ride height changes by half the diameter difference: +1.20 inches of ground clearance at the axle.

Other comparisons