Radial and Bias Ply TiresLast Updated August 8, 2023 | Meghan Drummond
Radial and bias ply tires both have applications today and depending on how you use your vehicle, one or the other may be more appropriate. Understanding the difference between radial and bias ply tires can help you pick the right tires so that you can be truly happy with how your Mustang drives.
Whether you’re a classic Mustang enthusiast trying to get a period-correct look or trying to figure out how your tire’s construction affects your drag performance, there are options available for every application.
Radial tires have steel belts that run around the tire, at a 90-degree angle to the center line. Meanwhile, bias ply tires have nylon belts that run at a 30-45 degree angle to the center line. As you can imagine, that makes radial tires significantly tougher and heavier than bias ply tires.
In 1968, Consumer Reports declared radial tires the clear safety winner, and since then they’ve come to dominate most markets. This makes sense; for most drivers, radial tires are the correct choice.
Radial tires tend to run cooler, which makes them better for long road trips. The steel belts lead to an overall toughness so that you won’t get a flat just because of a sharp rock. Because they’re so tough and the belts run perpendicular to the treads, they get a longer tread life.
The flexible sidewalls also make radials a better choice for cornering.
Radial construction forces a consistent pressure throughout the entire tire, which leads to better gas mileage in addition to better tread life. This even pressure distribution also leads to a smoother ride.
Radial tires are the ideal choice for daily drivers as well as long-distance trips since they can dissipate heat more easily, get better fuel economy, and are more resistant to flats.
Bias Ply Tires
So, you might be wondering why anyone would pick a bias ply tire considering all of the clear advantages of the radial tire. Bias ply tires are an older style, but they’re still being manufactured because there are some tasks that are better served by them.
Bias ply tires were the stock option for most ‘60s and ‘70s cars, and many still prefer their handling characteristics. Bias ply tires have a firmer road feel, which is interesting because they have a softer sidewall that creates interesting properties in terms of roll and with regard to cornering.
But mostly, people pick bias ply tires for stock competitions because they like the look of them. Bias ply tires have a characteristic bulge that for many is an important part of an authentic-looking classic car.
The first generation Mustang came almost exclusively with bias ply options. This guide to first-generation Mustang tires and wheels reviews the sizes and construction of the tires and wheels that were available at this time.
Modern bias ply tires have an attribute that makes them suited to drag racing: The sidewall wrinkle. When a drag race starts and power is sent through the rear wheels rapidly, a bias ply tire is able to wrinkle and absorb some of the impact so that the rear axle isn’t damaged. This is a valuable attribute, though it is also what makes many dislike the feel of bias plys on the street.
And when cornering is involved in a race, bias ply tires will be at a disadvantage.
Bias ply tires are often called drag racing slicks, and sometimes “balloon tires” because of their interesting flexibility and lack of traction when compared to modern radials. Even a slight jerk can make a driver have to fight to keep their car going straight with bias plys, but many consider the loss of stability to be worth it considering how much protection the wrinkle offers for the differential and transmission—both expensive parts to replace.
Many have recommended that drag racers with a manual transmission stick to bias plys, while automatic transmission drivers tend to select radials.
Mixing Radial and Bias Ply Tires
Given the strengths and weaknesses of both tire types, it’s only natural that some clever drivers have considered mix and matching in order to try to get the best of both worlds.
Unfortunately, that’s not quite how it ends up working in reality.
Mixing tires with different constructions or wear history can cause an unevenness in handling and response that can be dangerous, so you can imagine how dangerous it is to mix tires that handle everything from cornering to heat differently. Mixing tires, in general, is an idea that should be approached with care and consideration, mixing entirely different constructions like this is an idea best dismissed entirely.
Though we don’t recommend mixing radials and bias plys, there are other options for people who want the safety aspects of radial tires but don’t want to damage their car. Many drag radials are even Department of Transportation (DOT) rated for street use applications in addition to drag racing. That said, many DOT-rated drag radials are only just approved, and still would not be safe or recommended for running errands or daily commuting. Some of them have a tread depth that’s so minor that using it as a daily would result in a total loss of tread in no time, and given the cost of a good set of drag radials, that’s not recommended.
Drag radials have a sturdy sidewall for cornering and ride, but they also have a “wrinkle wall” which allows them to absorb some launch power the way a bias ply tire would. This is a result of a softer than usual compound that creates a “soft radial.”
Because drag radials are so soft, you’ll also need less of a burnout to get them started.
Bias Look Radials
For those looking for stock applications as well, more manufacturers are making radials that have the look of bias ply. This is great for those who love the stock look of a vintage Mustang but who want to take it out riding as well.
These look almost identical to their bias-plyed inspiration, but have a firm enough sidewall that you won’t need to worry about cornering. Almost all competitions accept bias look radials as being “stock” as long as the other aspects are matched, but if you’re looking to compete checking the rules in advance is always a great idea since they can change.
Bias Ply vs Radial
Thanks to drag radials and bias-look radials, there are bias and radial options for nearly every application. Whether you prefer the excellent tread life of a radial or the unique feel of bias ply tires, you have a lot of tire options.
Regardless of the construction of your tires, you can improve your handling, gas mileage, and safety by inspecting them regularly for signs of uneven wear and making sure that they stay at a good pressure. If you end up purchasing white letter tires, check out our guide on how to remove the blue coloring from your new tires
Image Credit: AutoEvolution, Mustang 6G, Carlisle Brand Tires, Fastlane Classic Cars, Coker Tire