<VV> Tire Size and Construction Markings "R" vs "D" vs "B"

[aircooled6 at prodigy.net]

The old 185/80D-13 tires that were mentioned in an earlier note were indeed
bias ply tires and not load range "D", which was usually stamped elsewhere,
although now it is usually those numbers and letters right after the size on
the sidewall, like 85Q or some-such.

>From 1010 Tire.com

The "R" stands for Radial, meaning it has a radial construction. Radial
tires have ply cords that extend to the beads and are laid at 90 degrees to
the centerline of the tread, the carcass being stabilized by a
circumferential belt. Other possibilities include "B" for belted
construction and "D" for diagonal construction. This means the ply cords
extend to the beads and are laid at alternate angles less than 90 degrees to
the centerline of the tread.

>From TireRack.com

The R in the P225/50R16 91S size identifies that the tire has a Radial
construction in which the tire's body plies "radiate" out from the imaginary
center of the wheel. Radial tires are by far the most popular type of tire
today representing over 98% of all tires sold.
If the R in the size was replaced with a D (225/50D16), it would identify
that the internal tire body plies crisscross on a Diagonal and that the tire
has a "bias ply" construction. Tires using this construction are for light
truck and spare tire applications.
If the R in the size was replaced with a B (225/50B16), it would identify
that the tire body plies not only crisscross the tire on a diagonal as
before, but that they are reinforced with belts under the tread area. This
type of tire construction is called "Belted." Tires using this construction
are practically extinct.

Everett Wilson
North Richland Hills TX