Picture this: Your family sitting dejectedly on the roadside while you wait for BoatUS Trailer Assist or while one of you heads off to find a service center that can replace the trailer's damaged wheel bearings. This is not how you want to start your vacation. While servicing wheel bearings isn't the most exciting job, it can save a lot of lost fun-in-the-sun time — something few of us can afford to give up.
All grease is not created equal. Even grease labeled "marine" can be incompatible with use on boat trailers. Don't change the type you use unless you're cleaning and repacking bearings.
Today's wheel-bearing assemblies are no different from those of 20, 30, even 50 years ago. They still use grease as a lubricant and coolant, still employ caged rollers that roll on a pressed-in race, and still use a rubber-lipped seal to keep grease in and water out. What's changed is the grease that's used to lube them; today's greases, especially synthetics, can offer a longer bearing life and more forgiving environment against roller failure. In addition, there are more methods than ever before for protecting and greasing the bearings without actually changing the grease. While Bearing Buddy brand-name protectors have been available for several decades now, they've been improved several times over and have met many forms of competition. In addition, new types of lubrication have been introduced in recent years, and liquid-oil-bath systems offered by several manufacturers have become more popular.
Grease is nothing more than heavy motor oil with a thickening agent (usually soap) added. The thickener is what makes it stick to the metal it's lubricating, in this case, the bearings. Grease is produced and sold in a variety of viscosities, or thicknesses, ranging from 0 to 6, with 0 the softest (almost liquid) and 6 the hardest (like firm cheese). Most grease carries a 2 rating, which is like peanut butter.
Grease also carries a letter rating. The label G means it's certified for use in automotive wheel-bearing applications, while L means use on an automotive chassis (to lubricate, say, tie rods, universal joints, spindles, or steering knuckles). The letters A, B, or C typically follow, which mean Good (A), Better (B) and Best (C). So grease labeled GC is certified Best for automotive wheel- bearing use. Grease can carry both G and L ratings, meaning it's suitable for both chassis and bearing use. If the grease is labeled GC-LC, this means it received the highest possible rating for automotive chassis and bearing use. Greases displaying this rating meet OEM requirements.
Not all types of grease thickeners are compatible with each other. Therefore, not all greases are compatible, even when designed for the same usage. When replenishing old grease, select a type with either the same kind of thickener or one that's compatible. If you don't know what grease you're replacing, try to clean out the old grease, if possible. If you can't get the old grease out, put in enough new grease to push out as much of the old stuff as you can. Find the information you need about the kind of thickener used in your grease on the label or packaging. The manufacturer may refer to the thickener as the base, thickener, or soap.
The story today is not much different than it was years ago: Automotive bearing grease is OK in a pinch, marine wheel-bearing grease is better, and synthetic marine-wheel bearing grease is best. The name brands are familiar, with a few new players offering new formulations. Best advice: Use a high-quality synthetic marine grease that's water resistant, and do the best job possible cleaning out the old grease when repacking. Don't mix old and new greases if possible, and record what grease you're using, so you know what to apply when your bearings need a shot of the slippery stuff, but it's not yet time to do a complete repack.
Types of Grease
Here are a few greases you'll see on the shelves at your local auto-parts store, trailer shop, or marine dealer.
Disc/Drum Wheel-Bearing Grease
Especially suited for vehicle and trailer-wheel bearing applications. It's worth noting that unless specifically labeled, it's not waterproof or water resistant, so it's not the best grease for boat trailers, which are often submerged in water when launching and retrieving.
LMX Red Grease
A heavy-duty, premium grease rated for just about every application, including marine trailer-wheel bearings. It resists water well and sticks in place, so it's excellent in outdoor applications, but it isn't specially formulated for wheel bearings.
Marine Wheel-Bearing Grease
You guessed it! This is the one you should be looking for. Formulated for advanced water resistance, as well as use in high-speed bearings, this is the best grease possible for use in boat-trailer wheel bearings.
Molybdenum ("Moly") Extreme Pressure ("EP") Grease
This grease contains molybdenum sulfide, which allows it to maintain its properties under extreme pressure. Its best use is on parts that slide together or next to each other, while under pressure, such as brake calipers.
A general-purpose grease for use in home and shop, for lube points on vehicle chassis, farm equipment, and industrial machinery. Typically lithium-based, it's usually not water-resistant or waterproof, nor is it rated for use in bearing applications.
While it would work in a pinch for boat-trailer bearings, it's not the best grease for this application. White lithium grease is a popular multi-purpose grease. Its white color makes it easy to spot and also easy to tell when replacing old grease.