Bias Ply versus Radial

Bias ply (cross-ply)

Reinforcing cords in carcass extend diagonally across the tyre from bead to bead about 30 to 40 degrees angle to the equatorial plane of the tyre. Cords run at opposite angles in alternating layers.

Radial ply

A belted or circumferential restricted tyre in which the ply cords extend from bead to bead at cord angles between 65 and 90 degrees to the equatorial plane of the tyre.

Bias Ply	Radial Ply

Bias ply advantages

• Strong sidewalls, tough casing
• Good lateral stability (hill side work)
• Good in rough terrain - generally used in mining
• Good puncture resistance
• Easily repaired
• Easy to set up and maintain (pressure)
• No power delivery problems
• Lower purchase price

Bias ply disadvantages

• Poor life expectancy (50% of radial)
• Lack of flexibility in casing reduces traction
• Can't run at low pressures
• Profile of tyre increases soil compaction and reduces traction

Radial ply advantages

• Good high speed capacity
• Low heat build-up
• Low rolling resistance
• Large contact area
• Good grip, 40% greater than bias ply
• Good availability of sizes. Proliferation of sizes in the last 10 years has mostly been in radial (eg. 70, 65, 60, 55 series)

Radial ply disadvantages

• More prone to puncturing
• More difficult to repair
• Greater knowledge required for proper set-up and maintenance
• Tubeless technology more difficult to fit/repair in field

Rectifying power delivery problems (radial hop or radial bounce)

• Solution is often a slow and tedious procedure requiring patience. Often there is no single or easy remedy.
• Check lead: The lower the ratio (closer to 0 degrees) the less likelihood of power hop.
• Check air pressures for suitability to application. Often increasing air pressure in the front tyres, or even reducing pressure in rear tyres can have a good result.
• Ballast the tractor (always with cast weights) to achieve best tractor balance - all four wheels working as designed. Use water as ballast in tyres only after all cast weight options have been exhausted. Ballasting with water is discouraged because it's incompressible. Radial tyres perform better than bias plies because they can flex more. Putting water in a radial tyre reduces its ability to flex, losing its flotation and traction advantage.