Load Range versus Tire Ply Identification
By Midwest Traction on August 28, 2017
Tips & Advice
The difference between tire ply, ply rating, & load ranges can be confusing. Let us clarify what makes each one unique from the others.
The air inside a tire is what carries the load, not the rubber; the tire simply contains the air. Higher load ratings (aka ply ratings) mean the tire body is stronger and can withstand higher pressure, thereby increasing load capacity.
Originally, tire ply was constructed of multiple layers of cotton cord. More layers (plies) meant more load capacity. Materials used currently are much stronger, so they require fewer plies to carry the same air pressure and load. This reduces friction and, in turn, reduces heat build up, thus extending tire life. All manufacturers have to alter is cord size & strength, where previously extra plies were needed.
Confusion often begins when someone looks at an old trailer tire and attempts to buy a 4, 6, 8, or 10 ply replacement tire. It is impossible to find trailer tires today that will state this on the sidewall. Instead, use a load range (LR) designation, which represents an equivalent strength compared to earlier ply ratings.
Most current trailer tires manufactured only have 1-3 actual body plies (even those that are 10, 12 or 14 ply rated). Load ranges are equivalent to previous plies and are thus called “ply rated.” For example, a Load Range B (LRB) trailer tire is 4-ply rated, rather than 4 -ply; LRC is 6-ply rated, and so on. The following chart represents this comparison:
Load Range Ply Rating
Keep these things in mind as you replace your trailer tires. Don't forget: It's alright to increase load range or ply rating when replacing tires, but don't decrease. Never exceed the load rating of the wheel when going to a higher load range tire.