Bias vs. Radial Motorcycle Tires
Although many people think tires are circular rubber-made donuts, they are much more complex than their appearance suggests. Tires are made up of multiple layers of rubber, fabric, and synthetic compounds that each contribute to the strength of the overall product. There are two primary body ply tire structures for a motorcycle that you can choose from: bias and radial.
Each of these options performs differently on the road and provides a unique handling experience. Learning more about the structure of a tire and the differences between bias and radial body plies can help you understand the unique uses for each.
The Structure of a Tire
Tires are multi-layered but their overall round shape is due to the bead, a round steel cable that mounts to the wheel. It essentially acts as a frame for the rest of the materials. The inner liner is the inside area of the tire that looks like an innertube. Its job is to seal in air.
Synthetic cords called body plies are attached to the tire’s bead, providing strength and structure to the tire. They are typically made from interwoven nylon or polyester materials. In many tires, there is also a steel belt system that sits on top of the body plies. It serves as the backbone for the tread, helping the tire to grip the road without losing its shape.
The bead, inner liner, body plies, and sidewall make up the tire casing or carcass. This carcass is manufactured before any tread is added to the external portion of the tire.
All types of natural and synthetic materials make up these various components. From the rubber, carbon black, and silica that make up the carcass, to the steel belting system and nylon body plies, each tire is complex both in structure and composition.
On bias or “cross-ply” tires, the nylon fabric plies cross diagonally over the underlying cables. These plies extend from one side of the tire to the other and sit at an angle to the bead which they are attached.
This configuration produces a taller sidewall, rounder tire profile, and narrower road imprint. The rigid sidewall makes bias tires generally less versatile than modern tires.
Most motorcycle manufacturers used bias tires until the 1970s when radial tires took over. This shift happened because consumers wanted bikes that could go faster, and the cross-ply structure caused tires to overheat—especially while banking. Because they compromised the handling quality of the vehicles, radial tires became safer and more reliable options.
What Do Bias Tires Do Best?
Although they are primarily manufactured for off-road, cruiser and touring motorcycles, bias tires work better in certain conditions than their radial counterparts. The cross-ply structure works best for low to medium speeds.
When bikes go too fast, bias tires become deformed and do not grip the road properly. However, these tires do handle heavy loads better because of their rigidity and unyielding structure. They are perfect for off-road and cruiser motorcycles, but not so much for sport bikes.
If you have an older motorcycle that you use for casual cruising (i.e., not at high speeds), it is more than likely fitted with bias tires. They work well on shorter trips where you might encounter rough terrain. The overlapping plies create better sidewall protection, so bias tires are better at resisting punctures.
The ply overlay on radial tires is completely different. For these tires, polyester plies are laid perpendicular from bead to bead and do not overlap. Additionally, radial tires have a belting package, typically made up of crisscrossed steel, aramid, or fiberglass, that sits in between the plies and the tread. This layer of belting gives radial tires more structural integrity than bias tires.
The tread and sidewall on radial tires have completely independent configurations, allowing for different flexibility properties and versatility.
Radial tires have a wide road imprint due to their flexible sidewall. Their adaptability provides a more uniform and even wear on the tread, making them easier to maintain.
What Do Radial Tires Do Best?
For many motorcycle models, radial tires are the best option. They have a more flexible sidewall, which allows them to perform well at sharper turns while banking.
Radial tires can help a bike reach speeds above 150 miles per hour with minimal growth. They are more suitable and practical for sportier bikes that have multiple uses. Unlike stiff bias tires, radial tires adjust to the terrain and provide a smoother, more comfortable riding experience.
If you enjoy sport riding, or sport touring, radial tires are the best choice. They are more flexible, have better road grip, and last longer than bias tires which are primarily used for cruisers or off-road motorcycle models.
Whether your motorcycle requires bias or radial tires, let Dunlop Motorcycle Tires get your wheels exactly what they need. Contact us today to get started on an order and learn more about what would work best for your bike.