TruckTally

Tire size comparison

Put your stock size against the one you are considering. Diameter change, ride height, speedometer error and a read on whether it will rub.

Tire size comparison

Diameter change, speedometer error, and whether it will rub.

Should clear

Slightly larger than stock. Most owners run this without trimming, though full lock on a rough surface may touch the mud flap.

Diameter change
+0.63"
+2.0% — 32.07" to 32.71"
Speedometer at 70
71.4mph actual
Reads 2.0% slow — you are going faster than it says.
Ride height
+0.32"
Change at the axle, before any lift or leveling kit.
Section width
+0.39"
10.83" to 11.22"
Revs per mile
617
-12 vs. stock (629)
Odometer drift
1020real miles
Actual distance covered per 1,000 miles shown on the odometer.
  • Sits 0.32" higher at the axle and needs 0.32" more clearance at the top of the wheel well.
  • 0.39" wider overall, so roughly 0.20" more on each side unless you change wheel offset.

Stock sizes by truck

Ford F-150

  • 245/70R17
  • 265/70R17
  • 275/65R18
  • 275/60R20
  • 275/55R22

Chevrolet Silverado 1500

  • 255/70R17
  • 265/65R18
  • 275/60R20
  • 275/50R22
  • 275/65R18

Ram 1500

  • 265/70R17
  • 275/65R18
  • 275/55R20
  • 285/45R22
  • 275/60R20

Reading a tire size

In 275/65R18, the 275 is the section width in millimetres, the 65 is the aspect ratio — sidewall height as a percentage of that width — and the 18 is the wheel diameter in inches. So the sidewall is 65% of 275mm, or about 7.0 inches, and overall diameter is 18 + 7.0 + 7.0 = 32.1 inches.

Flotation sizes such as 33x12.50R20 skip the arithmetic and state the diameter directly: a 33-inch-tall, 12.5-inch-wide tire on a 20-inch wheel. Both formats describe the same thing, and the calculator above accepts either.

One catch worth knowing: the stated size is a nominal figure measured on a specific rim width at a specific pressure. Two different 33-inch tires can measure an inch apart in the real world, and every one of them shrinks slightly under load. Treat the numbers here as the comparison the manufacturer intends, not a caliper reading.

Common questions

How much bigger can I go without a lift?

On a stock half-ton pickup, roughly 3% over the factory diameter is a bolt-on swap. Between 3% and 5% you can usually get away with removing the front mud flaps or trimming the plastic air dam. Past that, plan on a leveling kit or wheel offset change, because the tire will contact the cab mount or the front bumper corner at full steering lock.

Do bigger tires make the speedometer wrong?

Yes. The speedometer counts wheel rotations and multiplies by the factory tire circumference. A larger tire covers more ground per rotation, so the truck is going faster than the display shows — a 3% larger tire reads about 68 mph when you are actually doing 70. The odometer under-counts by the same percentage.

Can I fix the speedometer after changing tire size?

On most modern trucks yes — the tire size is a parameter in the powertrain module, and a dealer or a handheld programmer can set it to match. Correcting it also restores the transmission shift points and the ABS and stability control calibration, which is the more important reason to do it.