Tire Size Box

295/40R17 vs 315/40R17

315/40R17 compared with 295/40R17

+2.4% diameter, +0.8" width

315/40R17 is 26.92" tall vs 26.29". Within the 3% rule, so usually interchangeable.

26.3"17" rim4.6"11.6" wide
295/40R17 (solid) compared with 315/40R17 (dashed outline), drawn to scale

With 315/40R17 tires, when your speedometer says 60 mph you are really going

61.4 mph

315/40R17 is +0.63 inches (+2.4%) in overall diameter. That is within the 3% most shops and makers allow.

295/40R17315/40R17Difference%
Overall diameter26.29"26.92"+0.63"+2.4%
Section width11.61"12.40"+0.79"+6.8%
Sidewall height4.65"4.96"+0.31"+6.8%
Circumference82.60"84.58"+1.98"+2.4%
Revolutions per mile767.1749.2−17.9−2.3%

Speedometer difference

If your vehicle came with 295/40R17 and you fit 315/40R17, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.5 mph+0.5 mph
30 mph30.7 mph+0.7 mph
40 mph41.0 mph+1.0 mph
50 mph51.2 mph+1.2 mph
60 mph61.4 mph+1.4 mph
65 mph66.6 mph+1.6 mph
70 mph71.7 mph+1.7 mph
75 mph76.8 mph+1.8 mph
80 mph81.9 mph+1.9 mph

Each size on its own

Questions

Which is bigger, 295/40R17 or 315/40R17?
315/40R17 is taller by 0.63 inches (26.92" vs 26.29"). 315/40R17 is wider by 0.79 inches.
Can I replace 295/40R17 with 315/40R17?
Usually, yes. The diameter difference is +2.4%, inside the 3% rule of thumb most tire shops use. Check that the wider or taller tire clears your suspension and fenders, and that its load index meets your placard.
How much will 315/40R17 change my speedometer?
When your speedometer reads 60 mph with 315/40R17 fitted (calibrated for 295/40R17), your real speed is 61.4 mph. Your odometer will under-count miles by about 2.4%.
Will 315/40R17 lift my vehicle?
Ride height changes by half the diameter difference: +0.31 inches of ground clearance at the axle.

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