These letters correspond to historical "ply ratings," which originally counted the physical layers of cotton canvas used to construct the tire. While modern tires use stronger synthetic materials and fewer physical plies, the ply rating system remains a standard industry equivalent for strength: * **Load Range B:** 4-ply rating (light-duty utility trailers) * **Load Range C:** 6-ply rating (medium-duty utility, watercraft, and small camper trailers) * **Load Range D:** 8-ply rating (larger utility trailers, mid-sized campers, and horse trailers) * **Load Range E:** 10-ply rating (heavy-duty equipment haulers, toy haulers, and large fifth-wheels) * **Load Range F:** 12-ply rating (extra heavy-duty commercial and agricultural trailers) Always look for the "ST" prefix on the tire size (e.g., ST205/75R15). ST stands for Specialty Trailer. These tires are built with stiffer sidewalls to handle heavy loads and prevent trailer sway, unlike Passenger (P) or Light Truck (LT) tires. ## How to Find Your Trailer's Required Load Range

Before purchasing new tires, you need to locate the manufacturer's specifications for your trailer. ### 1. Check the Certification Label Look for the federal certification label or VIN plate on your trailer. This is typically located on the left front side of the trailer frame or tongue. The label lists the Gross Vehicle Weight Rating (GVWR), the Gross Axle Weight Rating (GAWR), and the original tire size and load range recommended by the manufacturer. ### 2. Read the Existing Tire Sidewall If the certification label is missing or illegible, check the sidewalls of the tires currently mounted on the trailer. Look for the load range letter, which is usually printed next to the tire size or near the maximum load and inflation pressure specifications (e.g., "Load Range D" or "LRE"). ### 3. Calculate the Required Weight Capacity If you need to calculate the capacity from scratch, divide your trailer's GVWR by the number of tires on the trailer. For example, if you have a tandem-axle trailer (four tires) with a GVWR of 7,000 pounds:

* 7,000 lbs / 4 tires = 1,750 lbs per tire. In this scenario, each tire must have a maximum load capacity of at least 1,750 pounds. To ensure a safety margin, it is best to choose a load range that exceeds this minimum requirement. ## Selecting the Right Tire at Tractor Supply When shopping at Tractor Supply, you can browse trailer tires in-store or online. To make the right selection, follow these steps:

* **Match the Size:** Ensure the tire width, aspect ratio, and wheel diameter match your current rims (such as ST205/75R15). * **Verify the Load Range Letter:** Check the product details or the physical tire sidewall to confirm the load range letter matches or exceeds your trailer's requirements. * **Check the Weight Rating:** Look at the maximum load capacity printed on the tire. Ensure the combined capacity of all tires exceeds your trailer's fully loaded weight. ## Upgrading to a Higher Load Range Many trailer owners choose to upgrade to a higher load range (for example, moving from Load Range C to Load Range D) for added durability and peace of mind. While this is generally safe and beneficial, you must consider two important limitations: * **Wheel/Rim Capacity:** The wheels (rims) must be rated to handle the higher weight and the increased air pressure (PSI) of the new tire. A Load Range D tire requires more air pressure than a Load Range C tire. If your rims cannot handle the higher PSI, they can crack or fail. * **Physical Clearance:** Higher load range tires are sometimes slightly taller or wider. Ensure there is adequate clearance inside the fender wells and between tandem axles.

## Key Maintenance Tips for Trailer Tires Once you select and install the correct load range, proper maintenance is essential for safety: * **Maintain Maximum PSI:** Always inflate trailer tires to the maximum cold PSI listed on the sidewall. Under-inflation causes excessive heat buildup, which is the leading cause of trailer tire failure. * **Avoid Mixing Load Ranges:** Never mix different load ranges or tire sizes on the same axle. This causes uneven load distribution and unpredictable handling. * **Inspect Regularly:** Check your tires for dry rot, cracks, tread wear, and correct pressure before every trip, especially if the trailer has been sitting idle.