tire question

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pineneedle

Member
I am looking at buying tires. I have the choice of radial or bias ply. What are the advantages/disadvantages of each type? My Scout will be used both for street/hiway driving and for trail driving.

Pineneedle
 
There is a common misconception regarding bias and radial tires. Most people think bias and radial tires are different due to the steel belting. This is not actually the case. You can (although it is extremely hard) find a steel belted bias ply tire. The real difference in bias ply and radial is how the layers of polyester are applied. In a bias ply tire the polyester is applied at a 45* angle to the center of the tread, they alternate the tread with each layer in order to achieve the 90* angle that is required. The radial tire is different in that each layer of polyester is laid at a 90* to the center of the tread and overlapped. This design help the side walls of the tires become more flexible and thus a better ride as there is more give and also provides better grip to the road as the tire will “flex” thus promoting better adhesion to the road.

The aspect ratio of a bias ply tire and radial tire is also very different. Due to the side wall flex or lack there of the aspect ratio of a bias ply tire is some where in the 100% range meaning it is nearly or completely round. With a radial tire it is at or below 85% meaning there is a nice flat spot where the rubber meets the road so to speak. Here again this provides far superior road contact and adhesion.

Finally the major difference is the steel belting found in virtually all modern radial tires. The steel belting is a layer of steel mesh imbedded in the layers of polyester of the tire. This provides strength, cohesion, and shape retention to the modern tire. This is what takes the flat spots out of tires when they sit over night or during cold weather and allows the tire to have a better aspect ratio and still retain its shape.

In short there really is no comparison between radial and bias ply tires on a modern automobile. Now trailers are a different discussion. The only way you should run bias ply tires is if you are building a complete factory restoration that will not see the road very often. This is not just my opinion this is also the opinion of every car and tire manufacturer. There is a reason why no cars are made with bias ply tires today.

This May be a little long winded for a simple question, so here are the cliff notes.
Radial tires are far superior to bias ply tires. Buy the radials.
 
Chad,

thanks for the note. Given the points you make, why does a strictly off-road tire line like super swampers make some bias-ply tires?

Pineneedle
 
Strength of side wall, also the bias ply tires are arguablely more “sticky” off road. It also allows you to air down farther without as much side wall risk. However even interco (the maker of super swampers) state they are an off road tire. Taken directly from there web site where they list them as a rv tire.

1970 was the year when the world's first 78 series full traction tire was introduced. The original swamper tire is the most copied and imitated of all rv traction tires. The super swamper tsl, when compared to the swamper, offers even more ... Increased mileage, deeper treads, quieter, smoother ride, less rolling resistance and tougher sidewalls. Special order only.
 
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