Bias Tires vs Radial Tires

Car Tires vs Motorcycle Tires

The two basic types of tire construction are bias-ply and radial.  A tire's construction is the key to its performance.

Construction

Bias-Ply - The bias-ply tire is made of layers of rubber coated plies composed of textile cords, usually nylon, placed upon each other at approx 30 deg angles.  These plies are then wrapped around the bead wires which anchor the tire to the rim.  This forms the casing or the air chamber.  The plies are then covered with more rubber to form the tread patten.

Radial - The radial tire is constructed in two parts.  First a single layer of rubber coated steel cables arch from one bead to the other to form the tire casing.  Second, numerous rubber coated steel belts are place d in the crown, under the tread, to form a strong stabilizing unit.

Performance

Bias-Ply - The only way to increase the strength of the bias-ply tire is to increase the number of plies and the bead wires.  More plies means more mass, increasing heat retention, reducing the tire life. 

The bias-ply tire casing is constructed to form one working unit.  When the sidewalls deflect, the tread squeezes and distorts.  This makes the tire scrub or squirm, decreasing traction, operator control, and accelerating tread wear.  Since the tread is subjected to any flexing that occurs, the footprint, or contact patch, distorts.  This causes abrasion from the ground surface, which reduces the life of the tire.  All of these factors signigicantly increase fuel consumption.

Bias-Ply tires have reduced life due to fast wear, high fuel consumption and reduced grip and control.

Radial - To increase the radial tire's strength, larger diameter steel cables are used.  These steel cables help reduce punctures, tears and flats.  They also help distribute heat, resulting in a cooler running tire, improving fuel economy.

The combination of steel stabilizing belts and the single-layer radial casing allows the tread and sidewall to act independently.  The sidewall flexes easily under the weight of the vehicle, and its cargo while the tread provides even contact with the ground.  Greater vertical deflection is achieved with radial tires.  This is desirable because exteme flexing greatly increases resistance to punctures while protecting the operator and expensive vehicles.

The stabilizing steel belts and radial construction minimize tread distortion.  As the sidewalls deflect, the steel belts hold the tred firmly on the ground, minimizing tread scrub and greatly increasing tread life.  When negotiating curves and encountering side forces, the independent action of the tread an sidewalls keeps the tread flat on the road.  This will be like getting on a brand new bike.  Treat it as such and you will be fine.  Ignore it at your own peril.allows the tire to hold to its path.

Summary

Radial tires deliver longer life, have siginigicantly fewer flats, and provide better traction.

Other radial advantages include lower fuel consumption, improved operator comfort and machine operation due to increased sidewall deflection and reduced heat build up in the tire.

Radial tires are beginning to show their face in the motorcycle world.  The big heavy bikes like the Goldwing and the Honda VTX 1800 Cruiser run radials on both the front and rear tires.  Unfortunately they are the only ones.  Even the wider tires being run on custom jobs, and choppers as well as stock on the Suzuki models are bias-ply.  

Installing a high performance directional car tire on the rear of your machine is cause for caution.  The handling will change.  The way you ride will change.  Taking curves will change.  These things shortly will become part of your muscle memory for riding, and they will not be noticed.  But it needs to be stated that installing a car tire will be like getting on a brand new bike.  Treat it as such and you will be fine.  Ignore it at your own peril.

  

Information obtained from Michelin Tires Website 1999 Fact sheet.