Did You Know | 03 Apr 2022

Radial Tyres on Bikes - Advantages and Disadvantages

It is often believed that radial tyres are much better than bias tyres. But have you ever wondered why? Well, to understand this better, let's first quickly try and find out why the need for radial tyres arose in the first place. Until about 50 years ago, bias ply tyres were pretty much the only option available for vehicles. They were reasonably good in doing what they were made for, but engine technology was evolving fast during those times, vehicle speeds were increasing at a rapid pace, and the old design of the bias ply tyres wasn't quite able to cope with the extreme demands of the newer machines. Bias ply tyres had extremely stiff tyre walls, as the entire thickness of their plies ran from sidewall to sidewall, making their construction stiff, and unyielding to undulating surfaces. This made the ride of the vehicle very bouncy and jarring, especially at high speeds. Bias ply tyres also ran hot, as they were not able to dissipate heat efficiently. The tough sidewalls also meant that the contact patch wasn't sufficient when performance motorcycles were leaned over.

The carcass of bias ply tyres consists of nylon belts which uniformly run from the base of one sidewall to the base of other sidewall at a 30 to 45 degree angle with the central tread line. These nylon belt layers overlap each other, and cover the entire area of the tyre, including the sidewalls and tread. What that means in effect is that the stiffness of the sidewall is largely the same as the crown, or the tread area, making it a pretty stiff construction overall. With those tough sidewalls, the bias ply tyres have their own advantages in terms of bearing heavy load, but they also have many disadvantages, including poor heat dissipation, insufficient contact patch, profile deformation at high speeds, and an unyielding, stiff response over uneven surfaces.

Radial tyres were born to address some of these problems. Unlike bias ply tyres, radial tyres had steel belts which ran radially, or at 90 degrees to the direction of tyre travel, giving them their name. Even when these tyres have additional plies or steel belts, they are arranged in the same direction, making all the plies run parallel to each other. In addition to these steel belts, there are additional reinforcement layers in the tread area, which can be made of different materials, including steel, nylon or kevlar among others. What that means is that the stiffness of radial tyres on the sidewalls is independent of the stiffness these tyres offer in the tread area, or the crown of the tyre. In effect, the sidewalls of a radial tyre are often softer than its tread, allowing for more flex, and therefore better response and grip over various terrains. Having witnessed several technological enhancements over more than 40 years, radial tyres have reached a highly evolved state and offer some clear advantages over the traditional bias ply tyres. Depending on the materials used in the cord ply of the radial tyres, they can be classified as all-steel radial ply, half steel radial ply or fibre radial ply tyres.

Advantages of radial tyres

Radial tyres, in general, work well in applications where high speed, mid corner handling and faster rate of heat dissipation are the key requisites. These tyres, owing to their more flexible sidewalls, also offer a fantastic transverse contact patch, allowing the rider to lean in their motorcycle more aggressively. Here we have listed some of the major advantages radial tyres offer over their bias ply counterparts.

  • With their flexible sidewalls, the surface contact area of radial tyres is larger than bias tyres. While the footprint of a radial tyre isn't as long as a bias ply tyre, it is much wider, offering better grip while taking corners at sharp angles. These tyres are more suitable for cornering at higher speeds as the sidewalls can flex depending on the change in weight on the tyre when the bike is leaning into a corner. The tyre can quickly go back to its original shape once the motorcycle comes out of the corner and straightens up.

  • Radial tyres offer better grip not just around corners, but also in a straight line, both at high and low speeds. This also helps during braking and prevents the vehicle from skidding in wet conditions.

  • The pressure in the contact area on a radial tyre is more evenly distributed as compared to a bias ply tyre, allowing for a more uniform wear over time.

  • Just like the pressure, the heat is also uniformly distributed inside a radial tyre. This is why radials run cooler than bias tyres. The steel belts on radial tyres do a better job of dissipating heat than the nylon plies on bias tyres. Even at high speeds, the heat is not concentrated in one direction or one particular area of the tyre. This prevents the tyres from bursting at high speeds and increases the overall safety, and life of the tyre.

  • The sidewalls, as explained earlier, are independent of the cord ply and the crown, and hence, are more flexible. This enables the tyre to soak up any irregular deformities on the surface. This makes the ride quality more compliant, and cushioned, especially at higher speeds.

  • The material on the crown, or tread is harder in radial tyres, and coupled with the steel cord ply, the tread strength of a radial tyre is higher. This means that the tyre wears out slowly and lasts longer. Also, because of the harder tread material, the puncture resistance of the tyre, at least on the crown, is also relatively higher.

  • Since the cord ply of radial tyres radiate around the centre of the tyre, the plies are independent of the crown and other layers of the tyre. This results in low friction between the components and reduced rolling resistance. When there is lower rolling resistance, the overall fuel efficiency of the bike is enhanced.

  • At high speeds, the profile of a bias tyre gets deformed to an extent that it affects handling. Radial tyres, however, stay more stable at high speeds, due to their reinforced crown belt, allowing for better stability and control at high speeds.

Disadvantages of radial tyres

While radial tyres have many advantages, they do have some disadvantaged. Let's take a look at what they are.

  • The biggest disadvantage of radial tyres is the risk of lateral deformation. Radial tyres, though strong, do not perform as well when put under excessive weight. There is a risk of the tyre deforming or bulges forming on the sides if the vehicle is saddled with a lot of heavy load and proper pressure is not maintained. Due to this characteristic of radial tyres, they are often avoided in trucks and other heavy commercial vehicles.

  • Another disadvantage is again related to the softer sidewalls. If the vehicle is heavily loaded, say with two riders and a lot of heavy luggage in the form of panniers and top boxes, due to the lower lateral stiffness the bike might tend to sway. However, this will happen only in extreme cases where the weight carried is overly heavy, and optimum tyre pressure isn't maintained.

  • The production cost of radial tyres is higher as the process is more complex, requires more expensive materials and consumes more time. Although, it can be argued that the cost savings radial tyres offer somehow balance the extra premium.

As evident, the advantages radial tyres offer over their bias ply counterparts heavily outweigh their negatives. Radial tyres are a far better option for your motorcycles as compared to bias ply tyres, which are often considered obsolete for performance motorcycles. Not only do radial tyres perform better, but also work towards making your rides a lot more comfortable, enjoyable and safe.

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Comments (5)

Rakshit Jain

06 May 2022

subscribing for more blogs like these

Arun Chail

06 May 2022

Can radial tyres can be successful in HCV vehicles like car carriers


06 May 2022

Which radial tyre can I put at the front of my apache rtr 2004v, mystock non radial needs replacement soon.

Hareram kumar

17 Jun 2022

Hareram kumar


23 Jun 2022