Boat Trailers 101: Materials, Brakes, Hardware

You might think a trailer is a trailer is a trailer. Uh, no. Like so many other products, the quality of  trailers varies widely, and if you look closely in all the right places, you can spot the differences. As simple as it sounds, a decent rule of thumb when trailer shopping is, “you get what you pay for.”

Some trailers have bunks custom-made to fit the hull of a particular model, assuring good, even  support.

Some trailers have bunks custom-made to fit the hull of a particular model, assuring good, even support.

Cheap trailers wear out sooner than one that costs more up front. When you buy a trailer you can decide which route to take. Like so many other things, the key to a better trailer lies in the details. Crucial elements—and these are all choices you must make—are materials, support systems, braking systems, suspension, construction, and hardware.


Let’s begin with materials. There are two: steel and aluminum. Obviously steel is usually stronger, but because it is a ferrous metal, it will rust. Aluminum corrodes, but it won’t rust. Raw steel is a cheaper material than aluminum, but that doesn’t mean all steel trailers are cheaper than their aluminum counterparts. As a general rule, if you do all of your boating in freshwater, you can more easily get away with a steel trailer. It will rust if you leave scratches in the paint unattended, but a decent steel trailer should last the life of your boat if you maintain it properly.

Conversely, if you do your boating on the ocean or the Intracoastal Waterway, you should choose an aluminum trailer. They’re not as pretty as a steel trailer with paint that matches your boat and tow rig—think I-beam aesthetics—but as we mentioned earlier, they don’t rust.

You also need to choose the trailer’s support system: rollers or bunks. Rollers tend to make loading and offloading a bit easier, but they don’t cradle a hull like bunks do. Four Winns boat company, which makes its own trailers, engineers them so that the bunks align with the linear stringers to provide support in places where the boat is strongest.

Also, rollers do not distribute the boat’s weight the way bunks do. Boats that sit unused  on rollers for a long time—each winter, for example—can develop a “hook” in the running surface at the transom or other imperfections. And as much as you spent buying a boat that goes fast, and on modifications to make it go faster, the last thing you need is a tweaked bottom. Have we talked you into bunks yet?

Trailer Brakes

We’re also going to try to talk you into disc brakes for your boat trailer. Why? Disc brakes offer more surface area between the friction material on the pads and the rotors than drum brakes. Greater surface area and larger pistons equals more stopping power with less effort, and on today’s clogged freeways, that’s becoming more important.Disc brakes also flush more easily and have fewer nooks and crannies for salt water to hide.

There’s another decision you need to make: surge brakes or electrohydraulic. Boat trailers traditionally have used surge brake systems, which use the initial “surge” of your truck’s braking power to compress the piston in the master cylinder, which actuates the calipers. Lately, electric-over-hydraulic brakes have begun to appear on boat trailers. The system works more efficiently than surge brakes, and is common on campers, car haulers, and utility trailers. For boat trailers, which can lead hard lives in and out of the water, the jury is still out on this choice. Electric brakes haven’t been on boat trailers long enough for us to know their service history, and in such a case, we’d probably give the nod to surge brakes, which have a proven track record.

If you do your boateing in salt water, an aluminum trailer is a better choice than steel.

If you do your boateing in salt water, an aluminum trailer is a better choice than steel.

For suspensions, two types of systems are used and each has a record of reliability. Torsion-bar systems, in which a torsion bar runs inside the axle, allow for a lower ride height. The drawback is that the system is more costly than leaf springs, and it can hide early signs of rust.

Leaf springs have been used for centuries and they are solid performers. Be sure to get a setup that can handle the weight of your load. Three leaves are better than single leaves. Five leaves are better than three. Simple, really.

In terms of the number of axles, a single-axle trailer is cheaper to maintain than a dual-axle trailer. You can get away with a single-axle trailer for boats as large as about 21 feet or so. Beyond that point, it’s better to get a dual-axle setup.

Details, Details, Details

While you’re crouched beneath the trailer counting leaves, also make note of the trailer’s hardware. Does it have stainless Bearing Buddy caps or chintzy stamped steel caps that leak water into your bearings? Or does it have the really slick industrial, sealed oil-bath bearings, such as those that come on Extreme Custom Trailers. How thick is the metal? Are the welds neat and clean, or do they look like a third-grader laid them?

To avoid getting stuck with a poor-quality trailer, go to the end of the trailer and look at the thickness of the metal. Same thing for the cross members. All the structural components should be more than beefy enough to haul their intended weight, with strength to spare.  A lot of people are using thin stuff because it’s cheaper than thicker stuff.

The same goes for aluminum. When you look at aluminum, not only should you look at the thickness of the metal, but also look at the height and the width. See how much heavier a trailer you’re getting.

It’s also important to look at a trailer’s hardware. Lots of manufacturers used galvanized fasteners. Sure, they won’t rust anytime soon, but they can cause problems of their own, and need to be maintained.

When shopping for a trailer, you can tell a lot about them by paying attention to the details. Probably the best way to look at a lot of different trailer brands is as easy as going to a boat show. You’ll probably be the only one looking at trailers instead of boats, but it’s worth the effort. Yes, it seems like a lot to go through for a trailer, but the quality and details are what make for trouble-free trailering as the years wear on.



  1. Great article, as a field technician with over 20 years experience repairing all brands of trailers I would add the following advice.When buying a used trailer for a different boat than it was originally set up to support/ tow consider these common retrofit issues. Before choosing a used trailer you should measure the boat from the bow eye to the transom at the bottom. Then measure the bow stop to the rear of the support board on the used trailer. These measurements should be fairly close if not you will either need to adjust the boards or the winch base on the tongue to compensate. The second measurement is the width of the boat at waterline then measure between fenders on the used trailer for fit. 1. Is the undercarriage {axle} fixed or adjustable? Winch post/base also? The tongue weight is extremely important to a safe ride and your ability to adjust the load across the fulcrum point is limited to these adjustments. Movement of axle or position of the load in relation to axle.The latter requires the winch post to be moved or the bunk supports lengthened and or shortened or both. Most torsion axles are fixed as well as spring axles on aluminum trailers. Remember to light of a tongue weight will cause you to fishtail, too heavy can cause steering issues or a bent, tongue. Other factors include the winch strap should be leveled to the bow eye after that you still have the placement of the support underneath to the New hull to contend with also requiring adjustable brackets. Lastly is your local state DOT laws as the seller does not have to provide you with a compliant trailer that is up to the person who will now be towing it on the road. As always let the buyer beware.

  2. Dwight Price says:

    Good article!

    I recently bought a 1997 21′ Sea Ray Bowrider without a trailer.

    I am having a hard time finding any for sale. I’d like to buy a used one if possible.

    Any suggestions on where to look?

    I live just north of Philadelphia.

    Thanks. – Dwight Price

    • Lenny Rudow says:

      Hey Dwight – it’ll be tough to find a used trailer that fits the bill. Usually, the trailer stays with the boat and it’s rare that a boat of that age will be junked and leave the trailer behind. If I were you I’d try e-bay and Craig’s List but I wouldn’t have high hopes of finding one quickly; you’ll probably have to buy one new.

  3. ron chunn says:

    I have a boat trailer for sale, brand new never seen a boat.17 foot galvanized boat trailer. set up for sail boat. fully movable axle. no brakes. 68 inch extendable tongue. never been in water. needs new carpet do to sun exposure. new tires, all lights are intact and great shape. 1550.00 obo (3500.00 new) pls give me ac all at (eight 05) six 4 four one 5 seven seven> ask for Bill. photos available