Tire Size Box

315/65R17 vs 315/75R17

315/75R17 compared with 315/65R17

+7.5% diameter, 0.0" width

315/75R17 is 35.60" tall vs 33.12". More than the 3% rule of thumb, so check carefully before switching.

33.1"17" rim8.1"12.4" wide
315/65R17 (solid) compared with 315/75R17 (dashed outline), drawn to scale

With 315/75R17 tires, when your speedometer says 60 mph you are really going

64.5 mph

315/75R17 is +2.48 inches (+7.5%) in overall diameter. That is more than the 3% most shops and makers recommend.

315/65R17315/75R17Difference%
Overall diameter33.12"35.60"+2.48"+7.5%
Section width12.40"12.40"0.00"0.0%
Sidewall height8.06"9.30"+1.24"+15.4%
Circumference104.06"111.85"+7.79"+7.5%
Revolutions per mile608.9566.5−42.4−7.0%

Speedometer difference

If your vehicle came with 315/65R17 and you fit 315/75R17, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.5 mph+1.5 mph
30 mph32.2 mph+2.2 mph
40 mph43.0 mph+3.0 mph
50 mph53.7 mph+3.7 mph
60 mph64.5 mph+4.5 mph
65 mph69.9 mph+4.9 mph
70 mph75.2 mph+5.2 mph
75 mph80.6 mph+5.6 mph
80 mph86.0 mph+6.0 mph

Each size on its own

Questions

Which is bigger, 315/65R17 or 315/75R17?
315/75R17 is taller by 2.48 inches (35.60" vs 33.12"). 315/65R17 is the same width.
Can I replace 315/65R17 with 315/75R17?
It is not recommended without checking carefully. The diameter difference is +7.5%, 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 315/75R17 change my speedometer?
When your speedometer reads 60 mph with 315/75R17 fitted (calibrated for 315/65R17), your real speed is 64.5 mph. Your odometer will under-count miles by about 7.5%.
Will 315/75R17 lift my vehicle?
Ride height changes by half the diameter difference: +1.24 inches of ground clearance at the axle.

Other comparisons