Tire Size Box

315/25R19 vs 315/30R19

315/30R19 compared with 315/25R19

+4.9% diameter, 0.0" width

315/30R19 is 26.44" tall vs 25.20". More than the 3% rule of thumb, so check carefully before switching.

25.2"19" rim3.1"12.4" wide
315/25R19 (solid) compared with 315/30R19 (dashed outline), drawn to scale

With 315/30R19 tires, when your speedometer says 60 mph you are really going

63.0 mph

315/30R19 is +1.24 inches (+4.9%) in overall diameter. That is more than the 3% most shops and makers recommend.

315/25R19315/30R19Difference%
Overall diameter25.20"26.44"+1.24"+4.9%
Section width12.40"12.40"0.00"0.0%
Sidewall height3.10"3.72"+0.62"+20.0%
Circumference79.17"83.07"+3.90"+4.9%
Revolutions per mile800.3762.8−37.5−4.7%

Speedometer difference

If your vehicle came with 315/25R19 and you fit 315/30R19, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.0 mph+1.0 mph
30 mph31.5 mph+1.5 mph
40 mph42.0 mph+2.0 mph
50 mph52.5 mph+2.5 mph
60 mph63.0 mph+3.0 mph
65 mph68.2 mph+3.2 mph
70 mph73.4 mph+3.4 mph
75 mph78.7 mph+3.7 mph
80 mph83.9 mph+3.9 mph

Each size on its own

Questions

Which is bigger, 315/25R19 or 315/30R19?
315/30R19 is taller by 1.24 inches (26.44" vs 25.20"). 315/25R19 is the same width.
Can I replace 315/25R19 with 315/30R19?
It is not recommended without checking carefully. The diameter difference is +4.9%, 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 315/30R19 change my speedometer?
When your speedometer reads 60 mph with 315/30R19 fitted (calibrated for 315/25R19), your real speed is 63.0 mph. Your odometer will under-count miles by about 4.9%.
Will 315/30R19 lift my vehicle?
Ride height changes by half the diameter difference: +0.62 inches of ground clearance at the axle.

Other comparisons