Tires & Ratings

Tires & Ratings

Tires consist of combinations of rubber compounds, each with specific properties and functions. The rubber compounds used in tires vary based on the type of tire, intended use, and manufacturer’s specifications.

Some common compounds used in tire construction are:

  • Natural rubber: Derived from the sap of rubber trees. Excellent elasticity and durability. Primary material used in tire production.

  • Synthetic rubber: Man-made rubber compound. Used in tire production to improve specific properties, such as grip and wear resistance. Common types of synthetic rubber used in tires include styrene-butadiene rubber (SBR), butadiene rubber (BR), and polybutadiene rubber (PBR).

  • Carbon black: A type of carbon added to rubber compounds to improve strength, durability, and resistance to wear and tear.

  • Silica: Additive used to improve grip and handling, particularly under wet conditions.

  • Antioxidants & antiozonants: Added to protect the tire from damage caused by oxidation and exposure to ozone.

  • Fillers: Materials added to improve stiffness and cut costs. Examples include clay, talc, and calcium carbonate.

The National Highway Traffic Safety Administration (NHTSA) is responsible for establishing and enforcing safety standards for motor vehicles and their components, including tires. The NHTSA uses a Tire Identification Number (TIN) to identify tires that have been tested and rated for safety. A TIN appears on the sidewall of every tire sold in the United States. A TIN includes information about the manufacturer of the tire, tire model and manufacture date.

The NHTSA conducts tire testing and evaluation to determine how well tires perform under various conditions. Examples of key testing criteria include wet and dry traction, handling and durability. The agency assigns a rating to each tire based on its performance in these areas, using a scale of 1 to 5 stars. A higher star rating indicates better performance.

Rubber compounds used in tire manufacturing are rated by their specific properties and performance characteristics.

Tires are rated for speed and load capacity. The load capacity and speed rating of a tire are determined by several factors, including size and construction of the tire, intended use and manufacturer’s specifications. Tires must be inflated to the recommended pressure or pound-force per square inch (PSI) to ensure proper load capacity and performance.

Load capacity is rated using the load index and refers to the amount of weight a tire is intended to carry at a specific inflation pressure. A numerical value on the sidewall, load index value ranges from 0 to 279. Each value corresponds to a maximum load. Generally, the load index is provided by the tire manufacturer in a chart form. The chart lists the maximum load capacity for each load index value. (too long to include in this blog)

Additionally, a load range may be provided. Indicating the range of loads a tire is designed to handle, it is represented by a letter. A quick internet search can give you some information on your tire’s load ratings. However, be sure to check the manufacturer’s chart for the most accurate information. This will help avoid potential problems.

Speed rating, on the other hand, refers to the maximum speed at which a tire can operate safely. The speed rating is also indicated on the sidewall, by a letter. For example, “Speed Rating T,” corresponds to a maximum speed of 118 mph with proper inflation and when carrying a load.

The speed rating code ranges from “L” to “Y,” with each letter corresponding to a specific maximum speed. The most common speed ratings and their maximum speeds are as follows:

  • L: 75 mph (120 km/h)

  • M: 81 mph (130 km/h)

  • N: 87 mph (140 km/h)

  • P: 93 mph (150 km/h)

  • Q: 99 mph (160 km/h)

  • R: 106 mph (170 km/h)

  • S: 112 mph (180 km/h)

  • T: 118 mph (190 km/h)

  • U: 124 mph (200 km/h)

  • H: 130 mph (210 km/h)

  • V: 149 mph (240 km/h)

  • W: 168 mph (270 km/h)

  • Y: 186 mph (300 km/h)

Both speed rating and load capacity are determined under specific conditions, such as recommended PSI. Exceeding a tire’s rated speed or determined load capacity is dangerous and increases the risk of blow-outs or tire failure. Follow the recommended speed ratings, load capacity and other guidelines provided by the tire and the vehicle manufacturer.

Still, have questions about the proper tires for your vehicle? We’re here to help.

Give Busbee’s Trucks and Parts a call today at (803) 564 – 3228 or visit our website,


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