Truck Tire Sidewall Markings Explained: How to Read Every Number and Symbol

Truck tire sidewall markings may appear to be nothing more than a series of numbers, letters, and symbols, but each one conveys essential information about a tire’s specifications and intended use. From tire size and load index to the DOT code, speed rating, and maximum inflation pressure, these markings help determine whether a tire is suitable for a particular vehicle and application.

For commercial fleets and owner-operators, understanding truck tire sidewall markings is crucial for selecting the right tire, maintaining proper inflation, and operating within safe load limits. Looking only at the tire size while overlooking details such as load range or the DOT date code can lead to premature wear, reduced performance, safety risks, and unnecessary operating costs.

This guide explains how to read truck tire sidewall markings step by step, covering the most important codes and symbols you are likely to encounter. By learning what each marking means, you can make better tire decisions and identify potential issues before they turn into costly failures or downtime.

What Information Is Found on a Truck Tire Sidewall?

A truck tire sidewall contains much more than just the tire size. It serves as a permanent reference that identifies the tire’s specifications, performance limits, and regulatory information, helping fleet managers, technicians, and drivers select and operate the tire correctly.

Depending on the tire model and manufacturer, you may find the following information on the sidewall:

Tire size

Tire size – Indicates the tire’s dimensions and fitment (for example, 295/80R22.5, 11R22.5, 215/75R17.5).

Construction type – Indicates how the tire is built. Most modern commercial truck tires use radial construction, identified by the letter “R” in the size designation (for example, 295/75R22.5). If you see a hyphen (“-”) instead of an “R”—such as 10.00-20—it typically indicates a bias-ply tire, which uses a different internal construction and is more common in certain off-road or specialty applications.

Rim diameter – Specifies the wheel size the tire is designed to fit, measured in inches (for example: 17.5, 19.5, 22.5).

Load Index

Load Index (Single/Dual) – Indicates the tire’s maximum load capacity under specified conditions. On many commercial truck tires, it appears as two numbers separated by a slash (for example, 152/148). The first number is the load index for single-tire use on an axle, while the second applies to dual-tire use (two tires mounted side by side). The dual rating is typically lower because it reflects the tire’s certified load capacity in a dual configuration.

Speed Index

Speed Index – Defines the maximum speed at which the tire can safely carry its rated load. For commercial vehicles, this rating ensures the fleet operates within safe mechanical limits during highway transit. For instance, a tire with a speed symbol L is certified for a maximum safe speed of 120 km/h (75 mph), making it ideal for standard long-haul freight, while a tire marked with an M rating pushes that limit to 130 km/h (81 mph), a specification frequently required for modern high-speed expressways and passenger coaches.

Load Range

Load Range / Ply Rating – Indicates the tire’s structural strength and maximum inflation capability. While the older Ply Rating (PR) system counted actual physical fabric layers (e.g., 16PR meant 16 physical plies), modern commercial tires utilize high-strength steel belts and advanced synthetics to achieve those same capacities with far fewer layers. Consequently, Load Range (designated by letters like G, H, or J) is now the preferred standard, identifying a tire’s equivalent load classification and inflation limits rather than its construction. For instance, a Load Range H truck tire does not contain 16 physical plies, but it delivers the exact strength and performance of a traditional 16 PR tire.

Tread pattern

While a tire’s tread pattern name (such as X Multi Energy) is stamped boldly on the sidewall, most fleet operators mistake it for a mere marketing label. In reality, it is a critical technical indicator that dictates exactly how and where the tire must be operated.

Reading the tread pattern name reveals three operational facts:

• Designated Axle Position: The pattern design determines placement. Straight vertical grooves (rib-style) provide steering stability for Steer axles; chunky block or lug designs deliver traction for Drive axles; and reinforced shoulders withstand heavy turning stress on Trailer axles.
• Application Terrain: Smooth, shallow grooves optimize fuel efficiency during highway Long-Haul transit, whereas rugged, deep-block patterns provide cut-and-chip resistance for harsh On/Off-Road construction sites.
• Specialized Fleet Capabilities: Take the Michelin X Multi Energy in Figure 1 as an example. The word “Multi” confirms the tread compound is engineered to endure regional scrubbing, turning, and braking, while “Energy” denotes ultra-low rolling resistance for high-speed highway fuel economy.

Two truck tires with the same size, load range, and load index can deliver very different fuel economy and traction simply because they use different tread patterns and compounds.

Note: Every tire manufacturer utilizes a unique naming convention for their tread patterns. To determine if the specific tire line you are running is perfectly optimized for your fleet’s application, always consult your local authorized dealer or review the technical documentation provided directly by the tire manufacturer.

Maximum Load

Maximum load – States the highest permissible weight the tire can safely carry when properly inflated. On commercial truck tires, this is tied directly to the dual load index markings; for example, a tire marked with a 152/149 load index means it can carry a maximum of 3,550 kg (7,830 lbs) when used as a single tire on an axle, but drops to 3,250 kg (7,160 lbs) per tire when mounted in a dual configuration side-by-side.

Maximum inflation pressure

Maximum inflation pressure – Provides the maximum cold inflation pressure recommended by the manufacturer.

DOT code

DOT code – A unique identification code that includes manufacturing and traceability information.

Manufacturing date

Manufacturing date – Usually represented by the last four digits of the DOT code, indicating the week and year the tire was produced.

Safety and certification markings

Safety and certification markings – May include symbols or codes related to regulatory compliance, winter performance, tubeless construction, regroovability, or other approved service characteristics.

Understanding these markings as a whole—not in isolation—helps ensure the tire is appropriate for the vehicle, load, and operating conditions while reducing the risk of premature wear, safety incidents, and costly downtime.

What You Won’t Find on a Truck Tire Sidewall

The Critical Link Between Tire Pressure and Load Capacity

A tire’s load index does not represent a static weight limit; rather, it defines the maximum capacity achievable only when the tire is inflated to its corresponding maximum cold inflation pressure. As shown in the chart for an 11R22.5 (Load Range G) tire, air pressure directly dictates structural capability. For instance, in a single axle setup at a maximum inflation of 105 psi (720 kPa), the tire can safely support its full rated load of 2,800 kg. However, if that same tire underinflates to 70 psi (480 kPa), its safe load limit plummets to 2,050 kg—a massive 26.7% drop in carrying capacity. Operating a heavily loaded fleet on underinflated tires forces the sidewall to over-flex, generating extreme heat that leads to rapid tread wear, casing fatigue, and catastrophic tire blowouts.