"Old-fashioned” bias-ply tires still hold a significant corner of the agricultural tire market. While it’s hard to argue with the many benefits of radial tires, such as less soil compaction and more traction, there’s a reason that bias tires are still rolling strong. So let’s cut to the chase: Whether your next ag tire purchase is a bias or radial tire should depend on its application.

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Are you looking to replace tires on your chore tractor or your tillage workhorse? Are your fields flat or is your land full of steep hills? In order to decide on a tire, it’s important to first know the differences between these two categories and how their attributes affect their performance in the field.

Bias Tires: A Single Unit Design

Tractors were wearing out bias tires since the 1930s. Bias tires feature multiple plies of rubber in a diagonal pattern from bead to bead. Because of this construction method, the tread and sidewall of a bias tire function as one unit. This results in a stiff and strong sidewall that can fend off damage from stumps and rocks. And because they’re stiff, bias tires can offer excellent stability on hilly terrain. Let’s face it: not everyone’s land is flat, so it’s especially important not to gloss over this strength of bias tires.

(A quick note: Goodyear’s development of the LSW, or low sidewall, radial tire also provides more stable operation on hillsides. To learn more about LSW tires, click here.)

However, a bias tire’s stiff construction can lead to a punishing ride for the operator. And when the sidewall of the tire flexes, so does the tread. This tread deformation can lead to a smaller or distorted footprint, which can increase wheel slippage, reduce traction, and result in additional compaction in your fields.

A radial tractor tire is designed as a two-part construction allowing the sidewall of the tire to flex independently of the face or tread area of the tire. A bias tractor tire is designed with a single ply wrapped diagonally from one side of the tire to the other. This means that as the tire flexes, the face or tread of the tire deforms leading to faster, and sometimes more uneven wear.
A radial tractor tire is designed as a two-part construction allowing the sidewall of the tire to flex independently of the face or tread area of the tire. A bias tractor tire is designed with a single ply wrapped diagonally from one side of the tire to the other. This means that as the tire flexes, the face or tread of the tire deforms leading to faster and more uneven wear.

Radial Tires: Two-Part Construction for Improved Flexibility

If you glance at a tire’s size description on its sidewall and notice an R, you’re looking at a radial tire. Invented in 1946, radial tires have become the preferred choice for maximizing traction performance and carrying heavy loads in the field. Two-part construction is what sets radials apart from bias tires. The cord plies are arranged at 90 degrees to the direction of travel, and the under-tread area is wrapped around the circumference of the tire by radial belts of steel or fabric. With a radial tire, sidewall flex is not transferred to the tread, allowing for more even wear. This means the tread on a radial tire can last 2–3 times longer than a bias tire’s tread.

A radial tire’s construction allows for a larger, more uniform tire footprint in the field, which equals more traction and less compaction and wheel slippage. Basically, you’re getting more pull out of each engine revolution when your tractor is wearing radials. At the same time, you’re helping prevent yield-robbing soil damage from compaction.

So . . . Which Do You Choose?

Tires are no different from a new auto-guidance system for your tractor: technology comes with a price tag. Durable, dependable bias tires are perfect for chore tractors. Cutting hay, powering augers or feed grinders, chopping corn stalks . . . these workhorses deserve a quality tire, but might not benefit from the increased efficiency a radial tire offers, especially when you factor in the purchase price.

On the other hand, for major fieldwork such as tillage, carting grain, planting, and harvesting, investing in radials will most likely pay off. The radial category continues to expand every year as manufacturers introduce more IF/VF tires (designs that allow for even more sidewall flex and higher performance), which can move more weight at lower tire pressures for an even larger footprint.

A Summary of Bias Tire’s Pros and Cons

To review, here are the key differences between bias and radial farm tires.

Bias Tire Positives

•  Lower cost than radial tires

•  Stiff sidewall prevents swaying on hillsides

•  Can carry heavy loads

•  Durable sidewall protects against punctures from rocks, sticks, etc.

Bias Tire Drawbacks

•  Rougher ride for operator both in the field and on the road

•  More compaction and rutting in fields

•  2–3 times shorter tread life

•  Less traction/more slippage

•  More fuel consumption 

When deciding between the two tire categories, it’s important to consult an expert who can find a tire match for your application and budget. If you want to know which tire is right for your operation, give NTS Tire Supply a call or drop us a line.

Posted 
June 15, 2019
 in 
Knowledge Guide
 category.

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