Tyres are classified according to their
2- Bias or Diagonal or Cross Ply.
In Radial tyre, ply cord, either steel or fabric, run straight
across the tyre from bead to
bead. In addition, the radial tyre has a belt of additional plies,
usually steel running
down the centre of the tyre between the carcass and the tread. This
construction allows the radial sidewall to be much more flexible
while the tread is much stiffer than bias ply tyres. This allow the tyre to absorb impacts and limit sideways movement of the tread
In the Bias ply tyre, also known as diagonal ply tyre, plies run
from bead to bead at an
angle (hence the name bias). With layers of plies criss-crossing
each other. This
construction makes the sidewall relatively stiffer and the tread area softer.