33-inch tires

Metric tire sizes name section width in millimeters, sidewall height as a percentage of width, and wheel diameter in inches. Overall diameter comes from the formula, rather than appearing directly in the size name.

Few metric sizes calculate to exactly 33 in. The comparison table includes sizes within 0.5 in of that diameter by the formula, alongside published maker measurements where available. Nominal calculations describe unloaded dimensions, not an exact measurement of every tire carrying that size.

For a 16 in wheel, 285/75R16 and 305/70R16 both calculate to 32.8 in. For a 17 in wheel, 255/80R17 is closer to the target at 33.1 in nominal. The commonly compared 285/70R17 is slightly shorter at 32.7 in by the formula.

For an 18 in wheel, 275/70R18 calculates to 33.2 in. For a 20 in wheel, 275/60R20 rounds to 33.0 in nominal. For a 22 in wheel, 275/50R22 calculates to 32.8 in, while 315/45R22 calculates to 33.2 in.

The linked size pages show each size separately. Use the comparison table to compare the other nominal diameters in this group, rather than treating every 33-inch label as the same dimension.

Published measurements can differ from nominal calculations. Firestone lists 32.8 in for the Destination X/T in LT285/75R16. Nitto lists 32.76 in for the Ridge Grappler in LT285/70R17, while Toyo lists 33.3 in for the Open Country R/T in LT295/70R17.

Flotation sizes state nominal diameter and width in inches. A 33x12.50R17 is nominally 33.0 in tall and 12.50 in wide; a 33x10.50R15 is nominally 33.0 in tall and 10.50 in wide. A 33x13.50R15 keeps that nominal diameter but specifies 13.50 in of width.

Those label dimensions are not substitutes for a maker's measured diameter and width. Check the exact model's entry in the comparison table when comparing physical dimensions.

By the formula, changing from 265/70R17 to 275/60R20 increases diameter from 31.6 to 33.0 in (803 to 838 mm), a 4.4% increase. Nominal revolutions per mile fall from 638 to 611. This example applies to that specific size change, not every tire called 33-inch.

With the original speedometer calibration unchanged, the calculated true speed is 62.6 mph at 60 mph indicated. At 100 km/h indicated, it is 104.4 km/h. The speedometer calculator compares other indicated speeds.

At 65 mph with a 3.73 axle ratio and a 1.00 transmission gear, calculated engine speed falls from 2,578 rpm to 2,470 rpm, down 4.2%. An axle ratio of 3.89 restores the original engine speed by the formula only.

The nominal diameter increase adds 0.69 in (18 mm) of ground clearance at the axle. The 4.4% diameter change exceeds the ±3% guideline used by tire shops. That guideline is a rule of thumb, not a law or a vehicle maker specification.