Today’s Lube Tip: Boat Trailer Wheel Bearings
Originally e-mailed on March 31, 2007.
I started to include this with Outboard Lubricants, but it was becoming too large, so I broke it apart.
General Discussion and Overview
I have tried to include a lot of detail here to attempt to answer everyone’s questions, though most of you will not need it all.
All bearing manufacturers prefer that bearings only be grease about 50% full (leaving substantial air space). Grease expands as it gets hot and full filled bearings will always tend to push grease out, and a full filled bearing will run hotter than a 50% filled bearing. However with boat trailer bearings being in the water every time you use them the air gap would draw/invite water in.
Therefore it is better for boat trailers to use a full-filled system and tolerate the expansion problems. I definitely recommend the use of “Bearing Buddy®” (Note: there are a number of different types of full-filled grease systems for trailer wheel bearings on the market. For boat trailers, the original Bearing Buddy® is the one I recommend. If you want more information on them their web site is www.bearingbuddy.com. They also have an addition for the seal that will really help control the grease leakage (info about it on their site). They have sizes to fit most wheel hubs used on boat trailers. (No, I don’t sell them or get any type of commission from them, they just do a better job than several other brands I have seen.)
The following is copied from www.bearingbuddy.com:
The axle hub is filled with grease until the grease forces the Bearing Buddy® piston outward about 1/8 inch. Because the piston is spring loaded, the piston exerts a slight (3 psi) pressure against the grease, which maintains a slight pressure between the inside of the hub and the outside environment. When the hub is submerged, water cannot enter the hub because of this pressure.
An automatic pressure relief feature prevents over-filling and over pressurization. Without this feature, the inner seal will be damaged. Grease can be added to the hub through an easily accessible grease fitting located in the center of the piston. Lubricant level (and pressure) can be checked quickly by pressing on the edge of the moveable piston.
If you can rock or move the piston, the hub is properly filled. Bearing Buddy® will last the life of your trailer.
The most aggravating can be the hub nut lock. I prefer the old fashioned castle nut and cotter pin but many boat trailers are now using several different lock/security systems for the hub nut now. If you don’t understand the nut lock used on your trailer, find out how it works before you disassemble it or damage it. I am not experienced on all the different locks used and will not try to cover them here. If yours uses a cotter-pin, roll-pin or similar, ALWAYS use a new pin when you reassemble. If yours uses a ‘nyloc’ or nut with a nylon fill (which is interference) ALWAYS use a new nut.
If you choose to use a standard lithium grease, always do a complete tear-down, clean, inspection and repack annually. However, if you change to AMSOIL grease, you may do a complete service only once for the life of your trailer.
Which Grease
There is a lot of difference in greases. The API (American Petroleum Institute) defines a “water-proof” grease by its water-wash-out by test procedure ASTM-D-1264 and allows 15% wash-out to still be called “water-proof.” In my opinion that is not very good, but it is their definition. I recommend AMSOIL’s Multipurpose grease (red) for boat trailers used exclusively in fresh water. It carries a water-wash-out rating of 1.8%! If you are in brackish or salt-water, then you need to move up to AMSOIL’s Water-Resistant (blue-green) grease 0.9% (of course this doesn’t apply to most reading this)! I have personally worked with many people with boat trailers for 25 years. Fishermen putting a trailer in the water 5 days a week year round have gone 10 years using AMSOIL without having to tear down after their first AMSOIL grease servicing, but merely giving their Bearing Buddy one or two pumps with a grease gun using AMSOIL red grease – every 5 times in the water.
Synthetic AMSOIL grease will greatly extend the life of your bearings, and greatly reduce the number of times you need to do the complete service.
Conventional petroleum based greases use a lithium base thickener with their petroleum oil in it. A lithium base is made by combining 2 different components.
Some ‘water-proof’ greases use a ‘urea’ base. Urea base greases cannot be mixed with any other types.
AMSOIL uses a lithium-complex which is made by combining 3 different components and makes a much stronger base, then uses the synthetic oils for the lubricant in them – so both the base thickener and the lubricant are stronger products. (Lithium complex is compatible to mix with lithium base greases.)
For fresh water only, the AMSOIL Multipurpose grease works well. Product code GLC-CR for a standard 14 oz gun tube ($5.05), GLC-10 for a case of 10 tubes ($49.50); or GLC-TB for an 8-oz toothpaste type tube ($5.05) or GLC-08 for a case of 12 ($59.40) of them.
For the Water-Resistant 0.9% rating use GWR-CR for a standard 14 oz gun tube ($6.00), GWR-10 for a case of 10 ($59.00).
AMSOIL store link to purchase on-line: http://www.amsoil.com/redirect.cgi?zo=52257&page=storefront/glc
Phone order retail: 800-956-5695, wholesale 800-777-7094 (use referral #52257) M-F 7:00a-5p Central
MC, VISA, Discover, and UPS to your door 1 or 2 business day delivery.
Or for personal service call me direct, Don Dawson 800-662-0532, no calls after 8:00p Central please.
It is only about twice the price of petroleum greases for far superior protection
Preparation
Note: this can be a “dirty” job, be sure to wear clothing that you don’t care if it gets stained. The more water-resistant the grease, the harder it will be to remove from clothing. If your bearing buddies are damaged be sure to get new. Always use new seals when you do a tear-down/inspection. Make sure to have plenty of clean rags or paper towels on hand. Using clean cardboard to cover your work area really makes easy clean-up. Also use clean cardboard at each wheel to help keep everything clean. If your grease has been left in an open container, throw it away, it has picked up dirt from the environment and that dirt will destroy your wheel bearings. If you are doing a complete inspection and service you will need approximately a tube of grease per wheel.
Cleanliness is extremely important to the life of your wheel bearings.
If you do accidentally get AMSOIL grease on something that you must clean, I have found that by first spot treating it with AMSOIL thin film Metal Protector (prod. code AMP-SC, $4.55), then secondly spot treat with liquid laundry detergent or liquid dish detergent, and finally put in the washer like normal. If you get it on a fabric car seat, first use the metal protector then use an upholstery cleaner. http://www.amsoil.com/redirect.cgi?zo=52257&page=storefront/amp
Disassembly and Cleaning
Loosen the lug nuts, jack up trailer, put it on jack stands or blocks for safety, and remove wheels. To remove your existing Bearing Buddy use a wood block against the edge of the Bearing Buddy and small hammer, tap, rotate to opposite side, and continue walking it off gently to avoid bending it.
Hub nut: if you aren’t familiar with your type of lock, pay close attention as you disassemble so you know how to reassemble it later, or have a friend assist who is familiar with it.
Remove the hub, and remove the seal discarding the old seal.
Keep track of which bearing comes from which position. When you reassemble later put them back in the same position, do not interchange used bearings.
Most parts can be cleaned by wiping thoroughly with clean rags/towels. You will want to clean the bearings with solvent. If you don’t have a parts cleaner, mineral spirits or paint thinner available at any paint store or home improvement center works well. A tooth brush makes an excellent tool to clean the bearings. If you don’t have an air compressor to dry them, let them air dry completely. If you do have an air compressor DO NOT spin the bearings to dry them, hold them still. Clean the inside of the hub and the spindle with rags/towels and discard ALL the old grease.
Inspect the bearing rollers and the outer races. If they are not 100% smooth and polished replace with new. Any visible wear is too much! If a bearing is worn, also replace its matching race, it probably has wear or scratches in it too.
To remove a race use a long punch reaching through the hub (most hubs have notches behind the race to make this easier). When installing a new race be careful to not hit the bearing contact surface. A large socket matched to the race size makes a good bearing installation tool.
Pre-Packing
Pre-pack the bearings and the excess cavity of the hub with clean grease. You can hand pack the bearings or if you have a dual cone packer it does a more complete and easier job. You will finish packing using the Bearing Buddy grease fitting later, but if you don’t pre-pack the largest volume of grease, you will probably damage the new seal by having to push too much air past it. Pre-packing just makes it easier.
Reassembly
Position the inner bearing in the hub, use a small wood block to install the new seal in the back of the hub. With most hubs the seal needs to be flush or even with the back edge of the hub. Check the quantity of grease in the hub cavity, you want it nearly to the inside diameter of the inside bearing. If you have too much it will be pushed out by the spindle and you can discard it then. (Some people prefer to position the outer bearing on its race before sliding the hub on, I prefer to wait.) Slide the hub over the spindle, slide the outer bearing in place, and replace the washer. Install the nut to a loose contact.
Adjust the Nut
This is critical! With AMSOIL synthetic grease you need to finish with zero lash (if you are using a conventional petroleum grease most mechanics prefer slightly looser). Bearing Buddy says do not use a ‘long fiber’ grease.
To achieve zero lash tighten the nut while spinning the hub (it is necessary to spin it to seat the bearings to the races, also to insure the seal is seated and not hung on the lip of the spindle). First tighten the nut very tight (by hand or using hand tools only) while spinning the hub, then loosen the nut and bring back to contact (you should be able to feel contact or zero lash fairly easily). I usually like to double and triple check my setting.
Some tech schools or some manuals may give you a torque setting for the hub nut, but I have had extremely good success using this method.
Install the lock. If yours uses a cotter-pin or roll-pin and zero lash doesn’t align to a setting, go to the closest loose setting (unless you are very close to the next tighter, then you might go to tighter by a very small amount).
Complete the reassembly
Use a wood block on the end of your bearing buddy and tap it back in place squarely.
Use your grease gun to finish full-packing the hub via the bearing-buddy grease fitting. Rotate the hub, pump grease, and repeat. It will take several times to expel the air and achieve a full-pack.
When finished you want the Bearing Buddy extended only 1/8 inch (instructions from their site). You need it extended some to keep slight pressure on the seal and keep water out, but you also need plenty of extension for the spring for expansion as the grease gets hotter so it won’t destroy and blow out the seal.
Especially if you have brakes on your trailer you should never over fill – that is compress the spring more than the 1/8 inch. You will be taking a chance of excess grease leaking into your brakes.
Maintenance
With AMSOIL Synthetic grease you will need to give your Bearing Buddies one or two pumps about every 5 times in the water (with conventional petroleum greases probably more often, perhaps every time or two times.
With AMSOIL most people never have to go through another tear down, even fishing 5 times a week for 10 years!
With petroleum greases, annual complete service is recommended.
Other Trailer Lube Points
Do you have a “tip-on/off” trailer? Check the tipping point. If it has grease fittings don’t forget to grease them. If it doesn’t have grease fittings use the ‘spray wax’ below.
Check your spring shackles/pivots. Some may have a grease fitting there.
Most boat trailers have a heavy double or triple galvanizing so the trailer frame shouldn’t have a corrosion problem, but the springs and shackles typically are not galvanized so they need protection. AMSOIL has a synthetic spray “wax,” Heavy Duty Metal Protector, that provides excellent protection. It dries to a hard coat so it doesn’t attract dirt, but penetrates and lubricates to work well on the springs and shackles. (It does leave a yellow-brown coating.) A 1 pound spray can costs only $6.60 and it goes a long way. http://www.amsoil.com/redirect.cgi?zo=52257&page=storefront/amh
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Tight lines and good fishing
Don Dawson, Your AMSOIL Dealer, Your Fishing Minnesota Lubricant Partner
