Budget Friendly, Low-Cost Truck, Bus (TBR) and Off the Road (OTR) Tyres

Useful Truck and Bus (TBR) Tyre Guide

Truck & Bus (TBR) Tyre Guide?

This guide is designed to provide you with a comprehensive understanding of your truck tire, including its size, load-carrying capacity, speed rating, and its suitable axle position.

Metric Truck Tire Sizes – 295/80R22.5, 315/80R22.5, 385/65R22.5

Modern radial truck tires feature metric size markings like 295/80R22.5, 315/80R22.5, and 385/65R22.5. To decode these markings:

  • The first number indicates the tire’s width when viewed from the front, expressed in millimeters (mm).
  • The last number represents the tire’s rim diameter in inches.
  • The letter ‘R’ signifies radial construction, which is the modern standard.
  • The number after the ‘/’ is the tire’s profile percentage, helping estimate the sidewall section’s height, crucial for calculating the overall tire height.

For example, a 295/80R22.5 tire has sidewall sections approximately 295mm wide and 80% tall, resulting in a total tire height of approximately 1043mm (41 inches). This profile is vital for maintaining axle heights, gearing ratios, and transmission performance.

Imperial Truck Tire Sizes – 10R17.5, 12R22.5, 10.00R20, 12.00R20

Some truck and bus tires still use imperial size markings such as 10R17.5 and 12R22.5. In this system:

  • The first number indicates the tire’s width in inches.
  • The ‘R’ or ‘-‘ symbolizes radial or crossply construction, respectively.
  • The final number denotes the rim diameter in inches.

For tires with ‘.00’ included, like 10.00R20 and 12.00R20, they often have a profile closer to 100%.

Truck Tire Axle Positions – Steer, Drive, Trailer, All Position

Truck tire requirements vary based on the axle they are installed on: Steer, Drive, or Trailer. Here’s a breakdown:

  • Steering Axle: Requires tires capable of handling turning stresses and providing precise steering response.
  • Drive Axles: Tires designed to handle power transmission and braking system stresses, often focusing on traction rather than high mileage.
  • Trailer Axles: Focus primarily on weight carrying. These tires are designed for high mileage, scrubbing resistance, and managing static and dynamic loads.

Selecting the right tire for your axle position ensures proper vehicle operation, compliance with road regulations, valid insurance, and maximizes the lifespan of your tire investment.

To further complicate matters, some tires can serve multiple roles depending on the vehicle type (Truck, Bus, Construction Vehicle) and usage (Regional, Long Haul, Urban, On-Off Road). These are often labeled as ‘All Position Tires,’ adding complexity to the tire selection process. We recommend confirming your required load and speed index, checking user manuals or manufacturer websites, and matching them with the intended axle position.

Load Rating / Speed Index – 143J, 156M, 160K

Modern radial truck tires display load and speed indices on the sidewall. These indices indicate the tire’s weight-carrying capacity and maximum speed:

  • The load index (the first number, e.g., 156) translates to kilograms (e.g., 156 = 4000 kg).
  • The speed index (the letter, e.g., M) corresponds to speed (e.g., M = 81 MPH).

For instance, a 156M truck tire can carry a maximum load of 4000 kg at a top speed of 81 MPH. Some truck tires have dual load and speed index markings, such as 156/152M, where the lower second 3-digit load index applies when the tire is mounted in a dual-wheel configuration on the axle.

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Truck Tire Tread Patterns – On-Off Road, Traction, Steering

Most truck tire manufacturers categorize their tread designs into the following main categories:

  1. Steering Tires: These tires often feature ribbed or grooved tread patterns to ensure precise steering and effective water displacement when needed.

  2. Traction Drive Tires: These tires typically incorporate larger square or rectangular blocks on the tread to provide enhanced grip and traction on the road surface, enabling efficient power transfer.

  3. On-Off Road Tires: These tires are characterized by more pronounced or deeper blocks on the tread, ensuring reliable grip in muddy or rocky terrain. They are often paired with robust shoulder sections to guard against scrubbing and other puncture hazards.

Effects of Incorrect Tire Pressure on Truck Tires

Neglecting proper maintenance of truck tire pressure can significantly reduce a tire’s service life. For instance, an underinflated tire by approximately 17% has been shown to result in a 10% decrease in the tire’s service life. Conversely, overinflation by about 20% can lead to a 22% decrease in service life due to uneven and suboptimal wear patterns. Moreover, underinflated truck tires can elevate fuel consumption, with studies demonstrating that a 10-30% underinflation can increase fuel usage by up to 3%, depending on tire usage.

Caring for Your Truck Tires

Truck tires are composed of a combination of rubber and metal materials that can deteriorate over time. The rate of deterioration depends on factors such as usage, storage conditions, and the prevailing climate (including temperature and humidity). To extend the life of your truck tires:

  • Keep them away from substances like oil.
  • Maintain the correct tire pressure as per manufacturer recommendations.
  • Routinely inspect your truck tires for any damage or signs of uneven wear.
  • If you discover any issues, have a professional truck tire expert conduct a comprehensive examination of the tread, tire sidewalls, bead area, and rim as necessary to ensure your truck tires remain fit for their intended purpose.
  • If you identify problems such as deformed or exposed bead wires, rubber delamination, or areas of internal creasing, do not continue using the tire and seek a replacement promptly.
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