### Read the Sidewall of Your Current Tires If your current tires are the original equipment and have performed well, you can find the size printed directly on the sidewall. Look for a code that starts with "ST," which stands for Special Trailer. For example, a common size code is **ST205/75D15** or **ST225/75R15**. * **ST:** Indicates the tire is specifically designed for trailers. Never use passenger car (P) or light truck (LT) tires on a trailer, as they lack the stiff sidewalls required to handle heavy loads and prevent trailer sway. * **Width (e.g., 205):** The width of the tire in millimeters. * **Aspect Ratio (e.g., 75):** The height of the sidewall expressed as a percentage of the width. * **Construction (R or D):** "R" stands for radial construction, while "D" or a bias dash indicates bias ply construction. * **Wheel Diameter (e.g., 15):** The size of the wheel rim in inches. ### Check the Trailer Certification Plate If the tires on the trailer are missing, worn beyond readability, or the wrong size, check the trailer's VIN plate or certification label. This metal plate or sticker is typically located on the left front side of the trailer frame. It lists the original tire size, recommended cold inflation pressure (PSI), and the Gross Vehicle Weight Rating (GVWR). ## Choose Between Radial and Bias Ply Tires
Tractor Supply offers both radial and bias ply trailer tires. Selecting the right construction type depends on how and where you use your trailer. ### Radial Trailer Tires Radial tires are constructed with steel belts running perpendicular to the tread. * **Best For:** Long-distance highway towing, frequent use, and travel trailers. * **Advantages:** They run cooler at high speeds, offer a longer tread life, provide a smoother ride, and are less prone to developing flat spots during storage. * **Disadvantages:** Typically more expensive than bias ply options. ### Bias Ply Trailer Tires Bias ply tires feature nylon cords that run at a 30- to 45-degree angle to the tread. * **Best For:** Short trips, agricultural use, construction sites, and heavy-duty utility trailers. * **Advantages:** They have stiffer sidewalls, which can reduce trailer sway under heavy loads, and they are generally more affordable. * **Disadvantages:** They run hotter at highway speeds, wear out faster, and can develop flat spots if parked in one position for long periods. ## Match the Load Range to Your Weight Capacity
The load range (or ply rating) determines how much weight an individual tire can safely carry at its maximum inflation pressure. Load ranges are designated by letters, such as B, C, D, E, or F. As the letter progresses down the alphabet, the weight capacity and maximum PSI increase. To calculate the required load capacity: 1. Locate your trailer's GVWR on the certification plate. 2. Divide the GVWR by the number of tires on the trailer. 3. Ensure the individual load capacity of the tire you choose exceeds this number. For safety, it is recommended to choose a tire load capacity that provides a buffer above your trailer's maximum loaded weight. Always maintain the maximum recommended PSI listed on the tire sidewall to ensure the tire can support its rated load. ## How to Find and Select Tires at Tractor Supply
Tractor Supply provides multiple ways to shop for trailer tires based on your convenience and immediate needs. ### Shopping Online Using the Tractor Supply website allows you to filter the inventory to find the exact tire you need. * Navigate to the trailer tires section. * Use the search filters to sort by tire size, wheel diameter, load range, and brand. * Decide whether you need a **tire only** or a **tire and wheel assembly**. Tire and wheel assemblies come pre-mounted and inflated on a steel rim, making them easy to install at home without specialized tire-mounting equipment. * Check local stock availability. You can set your local store on the website to see if the tires are in stock for same-day pickup, or if they must be shipped to the store or your home. ### Shopping In-Store If you prefer to buy in-person, visit the towing and trailer parts aisle at your local Tractor Supply. * Bring your tire size and load range information written down. * Inspect the tires or assemblies on the shelf to confirm the specifications match your requirements. * If you are unsure about compatibility, speak with a store team member to help verify the load ratings and dimensions before purchasing. ## Common Questions
### Can I mix radial and bias ply tires on the same trailer? No. You should never mix radial and bias ply tires on the same axle or on a tandem-axle trailer. Mixing tire constructions can lead to uneven tire wear, poor handling, and dangerous trailer sway. ### How do I know if I need to replace my trailer tires? Trailer tires should be replaced if the tread depth is worn down, if you notice cracks in the sidewall (dry rot), or if the tire has bubbles or bulges. Even if the tread looks new, trailer tires should generally be replaced every 3 to 5 years, as the rubber degrades over time from UV exposure and inactivity. ### What is the difference between an ST tire and a passenger car tire? ST (Special Trailer) tires are built with stiffer sidewalls and heavy-duty materials to handle the vertical loads and lateral forces unique to trailers. Passenger car tires have flexible sidewalls designed for traction and comfort, which can cause dangerous sway and tire failure if used on a trailer.
