It’s a decision that most old car enthusiasts face at some point in their lives — You know, choosing between tires with an old “bias ply” look or ones with the drivability of a radial…
In this article, we will look at the pros and cons of each option so that you can make the best decision for your needs.
Bias Ply Tires
The term “bias ply” refers to the internal construction of the tire. In a bias ply tire, the fabric cords run at a 45-degree angle from one edge of the tire to the other. As the cords are laid on during manufacturing, each subsequent layer is placed at a 45 degree angle to the one underneath it, creating a sort of crisscross pattern. After the tire is finished, the 45 degree angle ply construction leads to a narrow tread pattern with sharp shoulders and very little sidewall bulge.
Bias ply tires are firm and have handling characteristics that are very different than radials. They don’t hug the road quite as well and have sort of a “wandering” feel to them. This wandering isn’t dangerous, but it feels different to the average driver, especially at highway speeds.
Bias ply tires were used on American automobiles until the early 1970s, so if you are restoring a car from that era or earlier, they are an appropriate choice for achieving an accurate look and performance.
With radial tires, the internal plys run directly from bead to bead in a “90 degree” fashion, allowing them to conform to the road surface better than bias plys. This design makes for a more pleasant ride, especially on rougher roads that would otherwise cause bias ply tires to wander.
The folks at Mullahey Chrysler reminded us to keep in mind that radial tires have a wider footprint than the equivalent size bias ply tire. This increased contact patch offers more traction and better stability, while the rounded shoulder provides additional traction during hard cornering.
Radial tires also feature tread “siping”, which helps discharge water from the tread surface and increases wet weather traction.
Generally, radial tires are a popular upgrade for old car enthusiasts who like to drive their old car a lot and are less concerned about a period look.
Until now, old car enthusiasts have been faced with the age-old problem of choosing between bias ply and radial tires when restoring a classic car. Coker Tire, a major manufacturer of tires for classic cars, has come up with an innovation solution that gives you the best of both types of tires.
Their American Classic Bias Look radial tire has real 90 degree ply alignment but in a way that mimics the look of old 45 degree bias ply designs.
At the end of the day, the selection of tire type is a decision that every old car owner will have to make when looking to put a new set of tires on their car. The look of the tire is a personal decision that needs to be weighed against its handling performance. Typically those who drive infrequently and go to car shows tend to go for the old bias ply look, while those who enjoy their cars via frequent use usually lean towards radials.