Tire Size Box

315/30R19 vs 305/35R19

305/35R19 compared with 315/30R19

+3.6% diameter, −0.4" width

305/35R19 is 27.41" tall vs 26.44". More than the 3% rule of thumb, so check carefully before switching.

26.4"19" rim3.7"12.4" wide
315/30R19 (solid) compared with 305/35R19 (dashed outline), drawn to scale

With 305/35R19 tires, when your speedometer says 60 mph you are really going

62.2 mph

305/35R19 is +0.96 inches (+3.6%) in overall diameter. That is more than the 3% most shops and makers recommend.

315/30R19305/35R19Difference%
Overall diameter26.44"27.41"+0.96"+3.6%
Section width12.40"12.01"−0.39"−3.2%
Sidewall height3.72"4.20"+0.48"+13.0%
Circumference83.07"86.10"+3.03"+3.6%
Revolutions per mile762.8735.9−26.8−3.5%

Speedometer difference

If your vehicle came with 315/30R19 and you fit 305/35R19, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.7 mph+0.7 mph
30 mph31.1 mph+1.1 mph
40 mph41.5 mph+1.5 mph
50 mph51.8 mph+1.8 mph
60 mph62.2 mph+2.2 mph
65 mph67.4 mph+2.4 mph
70 mph72.6 mph+2.6 mph
75 mph77.7 mph+2.7 mph
80 mph82.9 mph+2.9 mph

Each size on its own

Questions

Which is bigger, 315/30R19 or 305/35R19?
305/35R19 is taller by 0.96 inches (27.41" vs 26.44"). 315/30R19 is wider by 0.39 inches.
Can I replace 315/30R19 with 305/35R19?
It is not recommended without checking carefully. The diameter difference is +3.6%, 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 305/35R19 change my speedometer?
When your speedometer reads 60 mph with 305/35R19 fitted (calibrated for 315/30R19), your real speed is 62.2 mph. Your odometer will under-count miles by about 3.6%.
Will 305/35R19 lift my vehicle?
Ride height changes by half the diameter difference: +0.48 inches of ground clearance at the axle.

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