How to Read Semi Truck Tire Sizes
To kick off our semi truck tire buying guide, everything you need to know about your vehicle’s tires is printed on their sidewalls in an alphanumeric sequence. As an example, if the sequence were 295/75R22, each part would mean the following:
- 295 refers to the tire’s width (in millimeters)
- 75 is the aspect ratio; the height of the sidewall is 75% of the tire’s width
- The R signifies that the tire is built with radial construction
- 22 indicates the wheel diameter measurement that the tire is built to fit (in inches)
You’ll also notice load index and speed rating symbols following the above information. These values help determine the maximum weight the tire can safely carry and the maximum speed it is designed to handle, respectively.
Tire Types for Semis
There are several different categories of semi tires, as detailed below, each of which is intended to go in a specific position on a truck or trailer:
Steer
Installed on the front axle, steer tires play a crucial role in handling, directional stability, and ride comfort. They feature a shallow tread pattern designed to reduce road noise and provide precise control over the vehicle.
Because steer tires directly impact braking and turning, they must be regularly inspected for uneven wear. High-quality steer tires typically include reinforced sidewalls to resist scrubbing during tight turns, so if you notice that your front tires are wearing unevenly, it’s likely the axle that needs an alignment.
Drive
Mounted on the powered axles of a semi truck, drive tires are responsible for transferring engine torque to the road. Their tread patterns are deeper and more aggressive than those of steer tires, often featuring block or lug designs that provide excellent traction in both wet and dry conditions.
Drive tires, in particular, are critical for maintaining fuel efficiency and reducing slippage. Their quality is especially important when operating in adverse weather or hauling heavy loads.
Additionally, drive tires are some of the most costly types of semi truck tires, and you’ll need to adhere to proper rotation schedules to extend their lifespan.
Trailer
Trailer tires are designed to carry heavy loads while providing good stability. Unlike steer or drive tires, however, trailer tires are not powered, so their tread designs prioritize rolling resistance and durability. They often feature ribbed patterns that reduce heat buildup and help the trailer track smoothly behind the tractor.
One thing to note about trailer tires is that they are subject to side scrubbing during tight turns, which is why they have reinforced sidewalls to reduce the risk of failure. Regular inspections are also essential to preventing blowouts, which can be incredibly dangerous at highway speeds.
All-Position
Lastly, all-position tires are versatile options that can be used in any axle position. They typically feature a ribbed tread pattern that provides a good mix of handling and traction, and they are especially useful for fleets that are seeking flexibility and simplified tire management. Investing in all-position tires can make it easier to keep up with inventory for multiple vehicles and pieces of equipment. And though they may not outperform specialized tires, they are a cost-effective and practical choice.
Factors to Consider When Buying
With the variety of tires thoroughly discussed, let’s now move on to the final section of our semi truck tire buying guide: the key areas to focus on when purchasing tires for your rig.
Buying semi truck tires involves more than just picking a brand name or the lowest price; several different factors impact the lifespan, performance, and safety of your vehicle. As such, when shopping for semi truck tires, you need to consider the following:
Load Capacity
Every semi truck tire has a maximum load capacity, which you can determine by checking its load index printed on the sidewall. Exceeding that limit can lead to issues such as:
- Overheating
- Blowouts
- Premature wear
The load index that you should choose for your vehicle will vary based on the Gross Vehicle Weight Rating (GVWR) and the type of cargo you typically haul. If your truck is generally used for long-haul trucking and loaded down to the max, you’ll need tires with a much higher load index.
Fuel Efficiency
Fuel costs are among the highest ongoing expenses for trucking operations, and tires play a major role in maintaining overall fuel efficiency. Low rolling resistance (LRR) tires are designed to reduce the energy needed to keep a truck moving, directly improving its miles per gallon and translating to substantial savings.
However, fuel-efficient tires may sometimes, to provide such efficient fuel usage, trade off an otherwise long tread life. With that in mind, you need to decide which factor is going to be most beneficial for your fleet.
Terrain & Route Conditions
The environment you operate in should also be something you consider. Long-haul trucks running mostly interstate routes need tires optimized for heat resistance and fuel efficiency, while haulers that encounter frequent stop-and-go traffic would likely benefit from tires designed for durability and even wear. And if you’ll instead be driving on mixed-service routes, such as through construction sites or logging operations, you may need tires with aggressive tread patterns.
You’ll also need to consider how road conditions change throughout the year in the area you work in. For example, if you expect seasonal snowfall, you’ll need tires that can handle such situations.
Smart Buying Decisions for Long-Haul Success
Although cutting corners on your semi truck’s tire quality may seemingly provide short-term savings, the costs of replacements and downtime can outweigh the benefits in little time.
On the other hand, making a wise buying decision can lead to long-term cost savings and a lower risk of unplanned downtime, both of which are great for your bottom line. Use the insights from our semi truck tire buying guide to make an informed choice when ordering your next set of tires.