Today, the technological advancement in the automotive sector and tyre engineering go hand in hand. However, owing to limited technological development, the same was not possible some decades back. After the origination of pneumatic tyres, the bias-ply or cross-ply construction tyres have ruled the wheel's rim for a very long period and were the only choice for automobiles till the late 1970s
Come 1980, radial tyres hit the market and went on to become popular among the carmakers. The main reason for their demand was bias-ply tyres couldn't withstand the ongoing technological evolution. Wherein, the hi-tech machinery was capable enough to attain high speeds however tyres could not support it. This was the major factor that turned the tables for radial tyres and made them a favourite in the automobile industry.
So the question arises, why we still find bias-ply tyres in some vehicles and not radial ones in every automobile? This and much more, you will get to know the answers once you read the difference between the radial tyres and bias-ply tyres.
Construction
Also known as 'radial-ply tyres', they are made using a mix of polyester and/or nylon plies that run from bead to bead straight across the tread area at a 90-degree angle. While plies run diagonally in the bias-ply tyres, overlapping each other in a criss-cross manner. To enhance durability, longevity and traction on the road surface radial uses steel belts/plies, while bias-ply come with nylon belts/plies.
Due to the unique construction of radial tyres, the sidewall and the tread function independently. Therefore, the flex of the sidewall is not passed to the tread, allowing the vehicle to remain stable and comfy during driving.
On the other hand, the bias-ply tyre with plies one above the other are thicker and less flexible compared to radial ones. Moreover, the criss-cross ply layout makes tread and sidewall to be interdependent. Hence, the flexing of anyone - sidewall or tread - affects the movement of the other, which may result in poor handling at high speeds.
Performance
The bias-ply tyres due to their construction offer smooth ride quality under rough road conditions. And can also bear heavy loads with immense ease without hampering the stability aspect. However, they are not dependable when it comes to high-speed drives.
Here is where radials pitch in as they offer optimum performance at high-speed alongside provide great cornering ability and comfort to the passengers. Thus, owing to the limitation of bias-ply tyres, they are not found on most of the passenger cars, but are fitted on commercial vehicles due to their extraordinary load-carrying ability.
Puncture and Cut Resistance
The unique construction process of the radial tyres prevents frequent punctures and cuts in and around the tread part. Moreover, if any injury occurs, only a small area of the radial tyre gets damaged. On the contrary, with the sturdy structure, the bias-ply tyres offer better resistance to cuts in the sidewall area. Similarly, if the tread area of bias-ply is affected it can reduce the strength and performance of the tyre by a good margin.
Radial tyres with integrated rubber-coated steel belts (90-degree angle) and independent functioning of the sidewall and tread call for toughened cut resistance. Further, the bias-ply tyres with their interdependent working (sidewall + tread) of nylon belts and criss-cross rubber-coated plies make sidewalls robust.
Traction
Better grip at high speeds is offered by the radial construction tyres that have firm tread and allow balanced weight distribution. Therefore, surefooted traction and optimum contact patch with the surface is always maintained. This also paves way for uniform wear and longer tread and tyre life. Moreover, with continuous grip radials ensure superior high-speed braking performance.
On the other hand, the bias-ply tyres with their interdependent sidewall and crown offer inconsistent grip if the sidewalls deflect. And also provide roll-over effect due to low grip during cornering. However, they offer excellent traction on uneven surfaces, low/moderate speeds and during highway cruising.
Ride Quality
The radial tyres are all about enhanced comfort and agile ride quality. In addition, they also bestow optimal control at high speeds allowing effective braking as and when required, courtesy, even contact patch and better grip.
With bias-ply tyres, agility during high-speed drives cannot be expected owing to their interdependent plies and tough sidewall formation. Comfort element is not ensured as sidewalls are not flexible enough to absorb bumps, however, are most required during heavy-duty haulage of trucks.
Heat Tolerance
Compared to the radial construction tyres, the bias-ply tyres are more prone to internal and external heating. Scientifically called tyre vulcanization temperature, every tyre is made to function within a prescribed temperature. Hence, during continuous usage, if the tyre exceeds the given maximum temperature it starts to wear gradually.
Keeping the same in mind, the hot air build-up while use should not go in excess of 25 percent of the cold pressure inside the tyre. Hence, checking excess heat built up through air pressure monitoring is vital during and after the operation.
Going by this principle, the radial tyres offer better heat dissipation and cooler running. That is the reason high-performance sedans/sports cars trust radials for their sprints, while trucks and trailers bank on bias-ply tyres for massive load transportation.
Should I Buy Radial Tyres or Bias-ply Tyres?
The bias-ply/cross-ply tyres are out-of-fashion now and are rarely demanded in the passenger car segment. Nowadays, masses insist on comfortable, hassle-free and safe drives, hence radials feature as OE fitted tyres in new cars. However, most commercial vehicles still trust the old-school bias-ply tyres for their load-oriented business due to its affordability and value aspect.
Although, some of the leading tyre makers are now manufacturing application-based particular kind of radial tyres for heavy-duty usage. Therefore, zeroing upon the choice of radial or bias-ply tyre is largely based on your application and conditions to which the tyre will be exposed.