Correctly sizing your trailer bearings is crucial for safe and reliable towing. This guide offers a step-by-step approach to identifying the right bearings, preventing premature wear, and ensuring your trailer is road-ready.
Understanding the Importance of Correct Bearing Size
The size of your trailer bearings directly impacts their load-bearing capacity, heat dissipation, and overall lifespan. Undersized bearings will overheat and fail prematurely, leading to wheel bearing failure, which can cause dangerous accidents. Oversized bearings, while seemingly beneficial, might not fit properly within the hub assembly, potentially causing uneven wear and reduced performance. Choosing the correct size ensures optimal performance and longevity.
Steps to Identify Your Trailer Bearing Size
The process of sizing trailer bearings involves several key steps. Each step requires careful attention to detail to ensure accurate identification.
1. Identifying the Axle
The first step is to identify your trailer axle. This is crucial as different axles are designed to accommodate specific bearing sizes. Information about the axle’s capacity and manufacturer is often stamped directly on the axle tube itself. Look for a metal plate or stamping containing this information. Common axle manufacturers include Dexter, AL-KO, and Lippert.
Knowing the axle capacity (e.g., 2,000 lbs, 3,500 lbs, 5,200 lbs) is a significant indicator of the bearing size required. Smaller capacity axles typically use smaller bearings. However, it’s not always a direct correlation, so further investigation is necessary.
2. Removing and Inspecting the Old Bearings
Safely jack up the trailer, secure it with jack stands, and remove the wheel and hub assembly. This will allow you to access the bearings.
Carefully remove the outer bearing, grease seal, and inner bearing. Note their positions as this will be helpful when reassembling.
3. Finding the Bearing Numbers
The most reliable method for sizing your trailer bearings is to find the bearing numbers etched or stamped directly onto the outer race of each bearing. These numbers are standardized and will allow you to order the correct replacements.
Carefully clean the bearings with a parts cleaner and a lint-free cloth to reveal the bearing numbers. The numbers are usually a series of digits (e.g., L44649, LM67048). Note both the inner and outer bearing numbers.
4. Using a Bearing Cross-Reference Chart
Once you have the bearing numbers, use a bearing cross-reference chart to confirm the dimensions and specifications. These charts are readily available online from bearing manufacturers and trailer parts suppliers. They translate the bearing numbers into crucial dimensions like:
- Inner Diameter (ID): The diameter of the hole in the center of the bearing.
- Outer Diameter (OD): The diameter of the bearing’s outer race.
- Width (W): The thickness of the bearing.
Confirm that the dimensions listed in the cross-reference chart match your physical measurements (if possible) for added assurance.
5. Measuring the Spindle (As a Last Resort)
If the bearing numbers are illegible or missing, measuring the spindle (the part of the axle that the bearings ride on) can help determine the correct bearing size. This method requires precision tools and careful technique.
Use a caliper to measure the following:
- Inner Bearing Spindle Diameter: The diameter of the spindle where the inner bearing sits.
- Outer Bearing Spindle Diameter: The diameter of the spindle where the outer bearing sits.
- Seal Surface Diameter: The diameter of the spindle where the grease seal sits.
With these measurements, you can consult a bearing chart to find bearings that match these dimensions. However, this method is less reliable than using bearing numbers and should be considered a last resort. Improper measurements can lead to incorrect bearing selection.
Choosing Quality Bearings
Once you’ve determined the correct bearing size, prioritize quality. Invest in reputable bearing brands known for their durability and performance. Cheap bearings can fail quickly, negating the effort you put into proper sizing and installation.
Frequently Asked Questions (FAQs)
1. What happens if I use the wrong size trailer bearings?
Using the wrong size trailer bearings can lead to a cascade of problems. Undersized bearings can overheat and fail quickly, leading to wheel wobble, axle damage, and even wheel separation. Oversized bearings might not seat correctly, causing uneven wear and premature failure. It’s crucial to use the correct size for safety and performance.
2. Can I use a bearing that’s slightly different in width?
Minor variations in width might seem inconsequential, but they can impact bearing preload and lubrication. Using a bearing with a significantly different width can lead to improper loading and premature failure. It’s best to stick to the exact dimensions specified for your axle.
3. How often should I repack my trailer bearings?
The frequency of bearing repacking depends on usage. Generally, it’s recommended to repack trailer bearings every 12 months or 12,000 miles, whichever comes first. However, if you frequently tow in harsh conditions (e.g., saltwater, dirt roads), more frequent repacking may be necessary.
4. What kind of grease should I use for my trailer bearings?
Use a high-quality, water-resistant, high-temperature wheel bearing grease specifically designed for trailer bearings. Lithium-based or synthetic greases are generally recommended. Avoid using general-purpose greases, as they may not provide adequate protection under the extreme conditions of trailer bearing operation.
5. How do I know if my trailer bearings are going bad?
Signs of failing trailer bearings include: excessive heat in the hub, a grinding or rumbling noise coming from the wheels, wheel wobble, grease leakage, and excessive play in the wheel. If you notice any of these symptoms, inspect and replace your bearings immediately.
6. Can I replace just one bearing in a trailer wheel?
While technically possible, it’s strongly recommended to replace both bearings (inner and outer) and the grease seal on the same wheel simultaneously. This ensures even wear and prevents one bearing from failing shortly after the other.
7. What tools do I need to replace trailer bearings?
You’ll need: a jack, jack stands, wheel chocks, lug wrench, socket set, bearing packer, grease gun, punch, hammer, bearing race and seal driver kit, and parts cleaner.
8. What is bearing preload and why is it important?
Bearing preload refers to the amount of internal load applied to the bearings during installation. Proper preload ensures optimal bearing performance and prevents excessive play. Too little preload can lead to bearing chatter, while too much can cause overheating. Follow the manufacturer’s instructions for proper preload adjustment.
9. How do I install new bearing races?
Installing new bearing races requires a bearing race and seal driver kit. This kit includes various-sized drivers that allow you to evenly press the new races into the hub without damaging them. Avoid using a hammer directly on the races, as this can cause uneven seating and damage.
10. What is the purpose of the grease seal?
The grease seal prevents grease from leaking out of the hub and contaminants from entering. A damaged or worn grease seal can lead to bearing failure due to lack of lubrication and contamination. Always replace the grease seal when replacing the bearings.
11. What if I can’t find the exact bearing number I need?
Contact a reputable trailer parts supplier or bearing specialist. They can often cross-reference alternative bearing numbers that are compatible with your axle. Providing them with the axle capacity and dimensions will help them find the correct replacements.
12. Can I upgrade to a different type of bearing (e.g., tapered roller to sealed bearings)?
Upgrading to a different type of bearing requires careful consideration and may not always be possible or recommended. Sealed bearings offer advantages like reduced maintenance, but they might not be suitable for all applications. Consult with a trailer specialist before making any significant changes to your bearing system. Ensure the new bearings are compatible with your axle and hub assembly.
By following these steps and understanding the importance of correct bearing sizing, you can ensure your trailer is safe, reliable, and ready for the road. Remember to prioritize quality parts and proper installation techniques for optimal performance and longevity.