Determining the correct trailer wheel bearing size is crucial for safety and performance. The most reliable method is to directly identify the bearing numbers stamped on the existing bearings themselves, or alternatively, to measure the Inner Diameter (ID), Outer Diameter (OD), and width of the bearing cups and cones if the markings are illegible or the bearings are missing.
Why Correct Wheel Bearing Size Matters
Trailer wheel bearings are the unsung heroes, allowing your wheels to rotate smoothly and efficiently. Using the wrong size can lead to catastrophic failures, resulting in wheel separation, accidents, and potentially severe consequences. Investing the time and effort to accurately determine the correct size is paramount. Neglecting this critical aspect puts both you and others at risk. Incorrect bearings lead to premature wear, increased friction, overheating, and ultimately, bearing failure. The cost of proper identification and replacement is negligible compared to the potential damage and liability caused by a preventable accident.
Methods for Identifying Trailer Wheel Bearing Size
There are several reliable methods for identifying your trailer’s wheel bearing size. Let’s explore them in detail:
Identifying by Bearing Number
The most straightforward approach is to locate the bearing numbers stamped directly on the bearing races (cups) and cones. These numbers are universally recognized and will allow you to order the exact replacements needed. These numbers are typically found etched or printed on the outer race and inner race of the bearing assembly.
- Where to Find the Numbers: Look for the bearing numbers on both the inner cone and outer cup of the bearing. They might be a combination of letters and numbers, such as “L44643” or “LM67048”.
- Documenting the Numbers: Note down the numbers from both the inner and outer bearings. There are often two different bearing sizes used in a single hub, one for the inner bearing and a different size for the outer bearing.
- Cross-Referencing the Numbers: Use these numbers to search online parts databases or consult with an auto parts dealer or trailer supply store. This will confirm the bearing size and provide compatible replacements.
Measuring the Bearing Dimensions
If the bearing numbers are worn off, damaged, or missing, you can determine the size by accurately measuring the bearing dimensions. This method requires precision and attention to detail.
- Required Tools: You’ll need a precise measuring tool, preferably a digital caliper, capable of reading measurements in millimeters or inches with at least two decimal places of accuracy.
- Measuring the Inner Diameter (ID): Measure the inside diameter of the inner race (cone). This is the diameter of the hole that sits on the spindle.
- Measuring the Outer Diameter (OD): Measure the outside diameter of the outer race (cup). This is the diameter that fits inside the hub.
- Measuring the Width: Measure the width of the inner race (cone). This is the distance between the two flat surfaces of the cone.
Consulting Your Trailer Manual or Manufacturer
The trailer’s owner’s manual is an invaluable resource that often contains detailed information about the trailer’s components, including the wheel bearing specifications. If you have the manual, check it for the bearing size. If you don’t have the manual, you can often find it online by searching for the trailer’s make and model.
Contacting the trailer manufacturer directly is another option. Provide them with your trailer’s Vehicle Identification Number (VIN), and they should be able to provide the correct bearing size information.
Important Considerations
- Never assume: Do not assume that the bearing size is the same as another trailer, even if they are similar models. Always verify the size using one of the methods described above.
- Bearing Condition: If the bearings are damaged or worn, it can be difficult to get accurate measurements. In such cases, it’s best to replace both the inner and outer bearings along with their corresponding races.
- Bearing Kits: Consider purchasing a complete bearing kit, which includes both the inner and outer bearings, races, and a grease seal. This ensures compatibility and simplifies the replacement process.
Frequently Asked Questions (FAQs) About Trailer Wheel Bearings
Here are 12 common questions and answers to further clarify the process of determining trailer wheel bearing size and related topics:
FAQ 1: What happens if I use the wrong size wheel bearings?
Using the wrong size wheel bearings can lead to premature bearing failure, overheating, and even wheel separation. This can cause serious accidents and costly repairs. It’s crucial to use the correct size to ensure safe and reliable performance.
FAQ 2: How often should I repack my trailer wheel bearings?
It’s generally recommended to repack your trailer wheel bearings every 12 months or 12,000 miles, whichever comes first. However, frequent towing, especially in harsh conditions, may warrant more frequent maintenance.
FAQ 3: What type of grease should I use for trailer wheel bearings?
Use a high-temperature, water-resistant wheel bearing grease specifically designed for trailer applications. Lithium-based greases are a popular choice. Avoid using general-purpose grease.
FAQ 4: How do I know if my trailer wheel bearings are bad?
Signs of bad trailer wheel bearings include excessive noise (grinding, rumbling), wheel wobble, uneven tire wear, and overheating hubs. If you notice any of these symptoms, inspect your bearings immediately.
FAQ 5: Can I replace my trailer wheel bearings myself?
Yes, replacing trailer wheel bearings is a task that many DIYers can handle. However, it requires some mechanical knowledge, the right tools (including a bearing packer), and attention to detail. If you’re not comfortable with this type of work, it’s best to have a qualified mechanic do it.
FAQ 6: What is a bearing packer and why do I need one?
A bearing packer is a tool used to force grease into the wheel bearings, ensuring that they are properly lubricated. Using a bearing packer is more efficient and less messy than packing bearings by hand. It also ensures that the grease penetrates all the crevices within the bearing.
FAQ 7: Should I replace the bearing races (cups) when I replace the bearings?
Yes, it’s generally recommended to replace the bearing races (cups) whenever you replace the bearings. The races and bearings wear together as a matched set. Replacing only the bearings can lead to premature failure of the new bearings.
FAQ 8: How do I remove the old bearing races (cups)?
Removing old bearing races requires a bearing race removal tool or a hammer and punch. Gently tap the race out from behind, working around the circumference to ensure even removal. Be careful not to damage the hub.
FAQ 9: How do I install the new bearing races (cups)?
Install new bearing races using a bearing race installation tool or a hammer and a driver that matches the race’s outer diameter. Gently tap the race into place, ensuring it is seated squarely and fully.
FAQ 10: What is a “buddy bearing” and is it necessary?
“Buddy Bearings” are a type of bearing protector designed to keep grease under pressure inside the hub, preventing water and contaminants from entering. They are not strictly necessary, but can extend bearing life, particularly in marine applications.
FAQ 11: How much torque should I apply to the spindle nut?
The correct torque for the spindle nut varies depending on the trailer and spindle. Consult your trailer manual or a reputable torque chart to determine the proper torque specification. Over-tightening or under-tightening the spindle nut can damage the bearings.
FAQ 12: What should I look for when inspecting new bearings before installation?
Before installing new bearings, inspect them for any signs of damage, such as cracks, dents, or rust. Ensure that the bearings rotate smoothly and freely. Apply a generous amount of wheel bearing grease to the bearings before installation. This initial lubrication is crucial for longevity.