TRAILER AXLES
(Paraphrased from a presentation given by Lawrence and Kelly from M^cCoy Bros. in 2000)

Gross Axle Weight Rating - The spindle is the weakest component of an axle and therefore the limiting factor in how much weight it can support. The springs are attached to the axle at the furthest outbound practical spot to take the most strain off the spindle. (Think of a basic lever). Generally this attachment is just behind the hub, leaving clearance for a tire. If your axle it not equipped with a GAWR decal and you are unsure how much weight it is rated for, disassemble one of your wheels and read the part number on the wheel bearing. A bearing supply house can then give you the weight bearing capacity of the axle. The last components are your tires. I suppose it can be argued that you don't require Indy 500 rated tires to go to Wabamun Lake, but at least check them for proper inflation before you start your trip. 

	After 50 KM check the temperature of the tires and the bearings.
	After 50 KM, rock the top of each wheel sideways to check for bearing play.
	When assembling a hub, ALWAYS replace the cotter pin with a new one.

It is unwise to operate your axle at 100% of rated capacity! Remember that if your trailer detaches and runs into someone else, you are liable. If your axle is bent, damaged or really bows under the weight of your boat, it is probably underrated for the load. The springs are probably OK if they don't flatten out. The simplest solution to this problem is to replace your old axle tube with a new one. They come cambered with spindles welded on. M^cCoy will measure your old axle and build a replacement unit that can be bolted on. I paid about $100.⁰⁰ for a 3500 lb. axle in 1999 which is relatively cheap compared to the repair cost out on the highway. Besides, peace of mind and all that! 

Axle Types and Comparison

	Spring mounted axles are the originals and ride harder than torsion axles. However, spring axles can be combined to make a tandem axle.
	A tandem axle transfers weight between the wheels to create a smoother ride over bumpy terrain. The equivalent in torsion axles is simply two axles, which ride rougher than a tandem spring axle.
	Either combination creates good directional stability.
	Since torsion axles run truer, the tires last longer.
	A spring-mounted axle operates with some noise. A torsion axle has no moving parts and operates dead quiet.
	With a torsion axle it is relatively easy to have a dropped axle for a sailboat trailer. This frees up the inside of the frame for the keel and lowers the center of gravity of the load.
	If salt-water corrosion is a concern, either axle type can be hot dip galvanized to solve that problem.
	The shackles and mounting bolts of a spring axle are made of mild steel. They are designed to wear out to seat in quicker.
	Adding shock absorbers to a sail boat trailer is NOT a good idea, as the trailer will ride hard when empty, resulting in accelerated wear of the mild steel components.

Springs and Shackles - If you have a single axle equipped with a sliding spring assembly that squeaks, it is NOT recommended to lubricate the back of the leaf to quiet the noise. They are designed to operate dry. If you oil the leaf the grit will stick and create a rather efficient grinding compound that will soon take care of the noise! I doubt you are looking for this type of solution. Instead, replace or add a nylon roller bushing to the bolt. Bushings are cheap. The same bushings can be added to shackles. In fact the bolts in a shackle are made of soft metal so they wear in to last longer in the gritty place they have to live. If you really enjoy lubricating bearings, brass shackle pins e/w grease nipples are available. The bushings are grooved to spread the grease uniformly. 

Electric Brakes - Electric brakes operate by energizing an electromagnet mounted on a lever inside the hub. When energized, the magnet is attracted to the inside of the brake drum and the rotation of the drum pulls the lever to push the brake pads out, thereby stopping the trailer. To create proportional braking, only a small amount of power is applied resulting in a weaker magnet. This is the job of the brake controller. Some controllers operate directly from hydraulic brake pressure. Others are equipped with an inertia sensor that applies proportional power as a function of deceleration. The latter type creates smoother braking in stop and go rush hour type traffic. The other advantage is that you don't have to cut into the brake lines of the tow vehicle to install it. The driver can manually operate either type.
- If the inside wall of the brake drum is not polished smooth, the electric magnet is not operating. Check the wiring or replace the magnet. Eventually the electromagnet requires replacing due to wear on the face. 

Surge Brakes - Surge brakes operate from an inertia sensor mounted on the tongue of the trailer. The mass of the sensor slides forward with deceleration, forcing fluid to the brake shoes. The advantage of this system is that the trailer brakes operate independent of the vehicle and require no connection to the tow vehicle. They also operate very smoothly. The disadvantage is that if the brakes of the tow vehicle fail, you simply have double the mass to stop, WITHOUT BRAKES. The driver cannot operate the brakes manually. The brake cylinders can also rust and seize, usually due to immersion in water. This problem is more prevalent in salt water. 

Axle and Bearing Lubrication - It is absolutely essential to maintain proper axle lubrication. A bearing lasts much longer if it is used regularly. The way most of us use our sailboat trailers (twice a year to/from the lake) is considered hard use. For this type of use it is recommended to repack your wheel bearings every three to four years.
TIP - Use lithium based or synthetic grease that resists washout with water. Synthetic grease has a very high EP rating that far exceeds mineral based grease or that the old ropy type of grease used in Red River carts. More important, it is lighter to penetrate quicker and more uniformly. This is the reason why trucks have switched from grease to oil in their axles, to decrease the rolling resistance on a cold winter morning. For all season use it reduces fuel consumption. It's the same reason why standard transmission manufacturers have switched from gear oil to automatic transmission fluid (Dextron II). The lighter viscosity oil, with a higher pressure rating, lubricates the top gears in the first turn of the transmission.
TIP - To further abuse the bearings, some trailers are immersed in water to launch the boat. (Imagine that). For this reason it is recommended to use a bearing buddy on the end of each axle to maintain grease pressure on the bearings. One thing that stands out in wheel bearings is that cleanliness is next to godliness. Therefore, use a bearing bra over your bearing buddy to keep the road grime out.
TIP - When launching your boat, DON'T immediately back your trailer into the water when you arrive at the lake. The problem is that the hot bearings will cool quickly when you immerse them. As the hot metal shrinks it draws the water into the voids in the hub. Instead, let the wheel bearings and axles cool while you ready the boat for launch. THE LAST THING YOU WANT IN THE BEARINGS IS WATER. This is probably THE compelling reason for totally filling the hub with grease AND using a bearing buddy e/w a bra. 

Off-Season Storage - It's an excellent idea to take the weight off the tires, bearings and springs when you store the boat on the trailer. Place wood cribs or jack stands under the frame so the tires just touch the ground. This is especially important if you park the trailer outside in the wind. The rocking movement squeezes the grease away from the bearing race and starts the pitting action. So, grease the bearings before storing the trailer on the stands. Some people advocate removing the wheels to totally remove the load from the suspension. However, if a stand collapses or the ground gives way, your boat will be damaged as the trailer drops. If you leave the wheels on the trailer it can't drop and your baby should survive OK.
TIP - Just as a side note, if you have to store the trailer in a grassy area, cut the grass short before you place the stands under the trailer. This prevents the dew in the grass from contacting the metal frame, causing rust. It also keeps the mice away because they are reluctant to expose themselves in the open area. In lieu of a cement pad, it is best to park the trailer on a stable gravel pad where the water can drain away. Use heavy planks under the tires to protect the tread.