What are the differences between radial and bias ply tubes?

Answer 1

Bias tires were the standard until the radial tire became the norm. The difference is in how they are constructed. Bias tires were typically constructed of 4 plys that run at angles to each other and the body of the tire and cross each other. Radial tires have the belts at a 90-degree angle to the tire, and the belts overlap rather than cross each other. Radial tires have another belt, usually of steel cord, running around the tire under the tread. Radial construction allows the sidewall of the tire to flex under loads without affecting the contact of the tread with the road unlike a bias tire that flexes very little. It is this flexing that requires you to use a radial tube in a radial tire. The tube is designed to handle the flexing without overheating as a bias tibe would.