Tire Size Box

205/30R19 vs 205/40R19

205/40R19 compared with 205/30R19

+6.8% diameter, 0.0" width

205/40R19 is 25.46" tall vs 23.84". More than the 3% rule of thumb, so check carefully before switching.

23.8"19" rim2.4"8.1" wide
205/30R19 (solid) compared with 205/40R19 (dashed outline), drawn to scale

With 205/40R19 tires, when your speedometer says 60 mph you are really going

64.1 mph

205/40R19 is +1.61 inches (+6.8%) in overall diameter. That is more than the 3% most shops and makers recommend.

205/30R19205/40R19Difference%
Overall diameter23.84"25.46"+1.61"+6.8%
Section width8.07"8.07"0.00"0.0%
Sidewall height2.42"3.23"+0.81"+33.3%
Circumference74.90"79.97"+5.07"+6.8%
Revolutions per mile845.9792.3−53.6−6.3%

Speedometer difference

If your vehicle came with 205/30R19 and you fit 205/40R19, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.4 mph+1.4 mph
30 mph32.0 mph+2.0 mph
40 mph42.7 mph+2.7 mph
50 mph53.4 mph+3.4 mph
60 mph64.1 mph+4.1 mph
65 mph69.4 mph+4.4 mph
70 mph74.7 mph+4.7 mph
75 mph80.1 mph+5.1 mph
80 mph85.4 mph+5.4 mph

Each size on its own

Questions

Which is bigger, 205/30R19 or 205/40R19?
205/40R19 is taller by 1.61 inches (25.46" vs 23.84"). 205/30R19 is the same width.
Can I replace 205/30R19 with 205/40R19?
It is not recommended without checking carefully. The diameter difference is +6.8%, 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 205/40R19 change my speedometer?
When your speedometer reads 60 mph with 205/40R19 fitted (calibrated for 205/30R19), your real speed is 64.1 mph. Your odometer will under-count miles by about 6.8%.
Will 205/40R19 lift my vehicle?
Ride height changes by half the diameter difference: +0.81 inches of ground clearance at the axle.

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