18.4R38 tire size

What 18.4R38 means

18.4-inch nominal section width, R radial, for a 38-inch rim. The bias-ply version is written 18.4-38. This is the older inch system; the metric equivalent is listed below.

Rolling circumference

207.0 in (5,258 mm)

RCI group

45 (about 70 in tall, rolling circumference ≈ 207 in)

Continental Agricultural Tires Technical Databook (measured values) and the Firestone Rolling Circumference Index chart.

Same height and width, same 38" rim: 480/80R38, 460/85R38.

600 mm (24.5")

600/65R38

520 mm (20.8")

520/70R38

Same height, other width — keeps front axle lead/lag about the same; needs the right rim width.

Full conversion →

Water, per tire

116.6 gal (441 L) = 973 lb (441 kg)

CaCl₂ 3½ lb/gal, per tire

1,184 lb (537 kg) total

CaCl₂ 5 lb/gal, per tire

1,259 lb (571 kg) total

Firestone hydroinflation tables, 16.0" rim. Other rims and tire counts →

• Tractor tire size conversion
• Lead/lag calculator
• Liquid ballast chart
• Axle load with implements