What Makes a Quality RV Trailer Frame?

There is no question that the RV trailer frame underneath your trailer or fifth-wheel will determine how it performs over time. A stout RV trailer frames means the ability to withstand the rigors of use, enabling you to get the biggest bang for your buck.

Common RV Trailer Frame Types

There are many different types when it comes to RV trailer frames but the most common are:

  • Tubular frame, (steel or aluminum)
  • I-beam, (steel)
  • Stamped frame (steel)
  • C-channel frame (steel
  • L-Channel (steel)

The structural integrity of any RV trailer frame or chassis will vary depending on the size, length and floorplan of the unit and its classification. For example; lightweight trailers with a gross vehicle weight rating (GVWR) of 5,500 pounds or less will probably use a 2-inch, 4-inch, or 6-inch aluminum tubular frame. The benefits in using aluminum are excellent structural support, a lighter weight compared to steel and rust-resistance. Another popular RV trailer frame used in lightweight trailers is called a stamped frame. An aluminum or stamped frame is a great design for smaller and lightweight trailers. More and more factories are incorporating aluminum in the overall design of their models to lower the weight, providing an easier towing experience for a wider range of vehicles and increased fuel economy.

A number of lightweight and ultra-light trailer manufacturers will use tubular or boxed aluminum in their chassis as well as throughout the entire structure. Other lightweight manufacturers may use an aluminum chassis but wood or substrate framing for the floor, roof, and side walls.

Types of steel chassis

When it comes to larger trailers or fifth-wheels, most manufacturers will use tubular steel, I-Beam, C-Channel or L-Channel construction for their RV trailer frames. Tubular steel is the most rugged and is used primarily in upper-end or very heavy products. I-beam construction is more prevalent in the industry, followed by C-Channel or L-Channel construction.

The strengthening members (cross members) that crisscross the frame can be made of steel or aluminum. For larger units we would recommend steel cross members that are set every 16 inches as compared to the more economical 24 inches on center. Asking your salesperson about the frame construction and cross member spacing will show him or her that you know what you’re talking about. The response will also tell you how much they know.

Don’t be surprised if some research is involved on their end. In a worst case scenario, get underneath the unit with a tape measure and check for yourself, if possible.

Pro Tip: How to Spot a Good Weld

Another important aspect of any RV trailer frame is the quality of welds and technique used. Some manufacturers may tack-weld portions of the frame. Others will use a bead weld at all intersections and cross members to the frame. Ask your salesperson about this but the only way to know for sure is to visit a factory to see for yourself how the frames are welded. Or, once again, climb under for a look. A proper bead weld will be 1-inch to 3-inches long as compared to short welds or tack welds. If the trailer frame has bolted joints, make sure that the bolts have lock nuts or retainers. Those will keep the bolts from coming loose when they are exposed to extreme vibrations. Welds are preferred over bolts in almost all scenarios.

Painted or powdercoated RV trailer frames

Once the frame is completed most factories will either paint or powdercoat the entire frame. They may only do so on the exposed areas. A frame that is 100% painted is preferred over a partially painted one and a powdercoated frame trumps a traditionally painted one. Powdercoating is applied via an electric charge and results in a uniform and impenetrable glaze-like finish. A painted frame is acceptable if applied by an experienced painter. But if it’s sloppily or quickly done, missed or lightly covered areas will soon succumb to rust.

While this sounds alarming, surface rust on a frame rarely results in loss of structural integrity. It may take years to develop in to a significant problem, but at that time the RV may be unsafe for travel.

A-frame designs

A-frame welded to cross member of chassis

A number of manufacturers weld an A-frame to the cross member of the chassis. Some will bolt and tack-weld the A-frame to the cross member for added support and strength. Some lightweight trailer manufacturers will use this type of design when attaching the A-frame to the chassis. In our opinion it’s not a bad design for lightweight trailers. But, if you’re considering a larger trailer you may want to consider the other two designs below.

A-frame attached under the frame/chassis

Some manufacturers will place the A-frame under the chassis and weld it to the chassis. Here again some manufacturers may bold and tack-weld the A-frame under the chassis for added strength.

Many RVers are happy with the results of this setup. Some believe this is the best design as compared to welding to the cross member only. This design is used for larger or heaver trailers. The only negative with this design is it does limit the amount of clearance between the chassis and the road. That could be problematic for those interested in traveling off-road.

A-frame design that goes through the cross member of chassis

Other manufacturers like Lance, Northwood, and Outdoors RV, use a different approach to attach the A-frame to the chassis. In this design the A-frame goes through the front cross member of the chassis and is then welded to the sides of the chassis. Some call this the “Integrated” A-frame design. Because the A-frame passes through the cross member and then is welded to the cross member and chassis some believe this provides superior support and will ultimately produce a much stronger A-frame. This results in eliminating any possibility of weakening or failing due to traveling on bumpy roads or off-road use.

We recommend either the Integrated or under-the-frame design when purchasing a trailer with a GVWR of 4,500 pounds or more. The integrated design does provide more ground clearance between the road and chassis, which can be helpful when traveling off-road.

Ask your salesperson about the A-frame design of the trailer you’re considering, but also get on your hands and knees for a look. Aside from a tape measure and flashlight, some old clothes are recommended when shopping for an RV. Understanding how the A-frame is attached to the chassis will help you determine if this is the right brand or model for you. While an Integrated frame is preferred, it is also more labor-intensive to build, hence more expensive. For snowbirds or full-timers, the expense will be justified; for a weekender, the added strength and integrity of the frame may likely be unnoticeable.

Fifth-wheel frame/chassis

Most fifth-wheel manufacturers will use tubular steel or I-beam construction when building a fifth-wheel frame. The portion that extends up and out (hitch end) requires added steel and reinforcement to adequately support the weight of the entire frame. When shopping for a fifth-wheel, ask your salesperson about frame design and the type of steel being used. Is the entire frame painted or powdercoated? What structural features has the manufacturer incorporated into the frame? Again, don’t be surprised if your salesperson does not know the answers. Most people don’t ask these questions. However, most quality fifth-wheel companies will put a lot of emphasis on how well their frames are designed and salespeople selling high-end fifth-wheels should know the answers to these questions.

Ask the experts

Don’t just take our word for it. Ask the experts! If you’re looking for even more valuable how-to information, forums such as iRV2.com (check out the Chassis Clubs Forums) and blog sites like RV LIFE, Do It Yourself RV, and Camper Report provide all the information you need to enjoy your RV.