If you manage a commercial fleet, understanding tire size notation is essential for making smart purchasing decisions. The numbers and letters stamped on every commercial tire contain a wealth of information about that tire's capabilities. Let's break it all down.
Metric vs. Standard Size Notation
The two most common commercial truck tire sizes you'll encounter are 11R22.5 and 295/75R22.5. Despite looking completely different, these two sizes are actually interchangeable and fit the same wheels.
In the standard notation 11R22.5, the "11" represents the section width in inches, "R" means radial construction, and "22.5" is the rim diameter in inches. Simple and straightforward.
The metric notation 295/75R22.5 provides more detail. The "295" is the section width in millimeters, "75" is the aspect ratio (sidewall height as a percentage of width), "R" again means radial, and "22.5" is the rim diameter. This notation gives you a clearer picture of the tire's actual dimensions.
Understanding Load Ratings
Every commercial tire carries a load index number — for example, 146/143. The first number (146) is the load capacity in a single configuration, and the second (143) is for dual configuration. Higher numbers mean the tire can carry more weight. For an 11R22.5 tire, a 146/143 load index means approximately 6,614 lbs per tire in single and 5,357 lbs in dual.
Getting load ratings right is not just about performance — it's a safety and compliance issue. Running overloaded tires accelerates wear, increases blowout risk, and can result in DOT violations during roadside inspections.
Speed Ratings for Commercial Tires
Commercial truck tires typically carry speed ratings of L (75 mph) or M (81 mph). While most fleet operations stay well within these limits, it's important to match the speed rating to your application. Long-haul operations at sustained highway speeds need tires rated for that use.
What Does PR Mean?
The PR rating (Ply Rating) indicates the tire's load-carrying capacity relative to the number of plies in early bias-ply tires. A 16PR tire doesn't literally have 16 plies — modern radial tires achieve the same load capacity with fewer, stronger plies. But the PR number remains a useful shorthand for the tire's strength class. Most 11R22.5 tires are 14PR or 16PR, with 16PR being the standard for heavy-duty applications.
Common Commercial Tire Sizes
Beyond the ubiquitous 11R22.5 / 295/75R22.5, other common sizes include:
- 11R24.5 — Popular for drive positions, slightly larger diameter
- 285/75R24.5 — Metric equivalent of 11R24.5
- 315/80R22.5 — Wide-base single tire for trailer applications
- 225/70R19.5 — Medium-duty trucks and buses
- 245/70R19.5 — Medium-duty regional operations
When ordering tires for your fleet, always confirm the exact size currently mounted and consult your vehicle manufacturer's specifications. Mixing sizes on the same axle can cause driveline damage and uneven wear.
At Oryx Wheels & Tires, our team can help you navigate tire specifications and find the right Onyx or Royal Black tire for every position on your trucks. Contact us for expert guidance.
