How to Measure 5th Wheel Rails Guide

How to Measure 5th Wheel Rails Like a Boss

In the world of 5th wheel hitches, the term “industry-standard” is thrown around a lot, particularly when referring to 5th wheel rails. But what does that mean exactly?

In this guide, we’ll provide a definition of what industry-standard means for 5th wheel rails, which measurements that entails, how to measure your 5th wheel rails, as well as some points to consider when buying new 5th wheel rails for your truck.

What Does Industry-Standard Mean?

When 5th wheel rails are deemed as industry-standard, it means that they meet certain fixed measurements. Having these measurements consistent across the variety of base rail options makes the design and installation of hitches easier.

At a glance, these are the industry-standard measurements:

How to Measure 5th Wheel Rails DiagramHow to Measure 5th Wheel Rails Diagram

Let’s break down what each of these measurements mean. Every set of industry-standard 5th wheel rails adheres to three key measurements:

  • The distance between mounting points along each rail
  • The size of the mounting points themselves
  • The distance between the rails when mounted in the truck bed

Distance between Mounting Points

Distance between 5th Wheel Rail Mounts in InchesDistance between 5th Wheel Rail Mounts in Inches

For a set of 5th wheel rails to be considered industry-standard, they need to have three sets of mounting points: a narrow set, a medium set and a wide set. These mounting points are simply slots in the metal rail that accept the anchoring tabs of the 5th wheel hitch.

Measuring along the rail, the narrow set of mounting points need to be 10” apart, the medium set 20-1/2” apart, and the wide set 29” apart.

When the mounting slots are positioned at these industry-standard points, it allows 5th wheel hitch manufacturers to design hitch legs and sliders with anchors that will match, ultimately resulting in a simple, drop-in installation for the user.

Size of the Mounting Points

Size of 5th Wheel Rail Mounting SlotsSize of 5th Wheel Rail Mounting Slots

A second criteria for rails to be considered industry-standard is the size of the mounting points; that is, the slots themselves.

Each slot needs to measure a minimum of 1-1/4” long and 1/2" wide.

Again, having these dimensions consistent allows 5th wheel manufacturers to engineer the anchoring tabs to match.

Distance between the Rails

Distance between 5th Wheel Rails 22 InchesDistance between 5th Wheel Rails 22 Inches

Every standard 5th wheel installation includes two rails mounted in the truck bed. Two rails allows for four mounting points for a stable hitch.

In order for a 5th wheel installation to be considered industry-standard, the two rails need to be positioned parallel in the truck bed at 22” apart. The measurement is taken center-on-center between two mounting slots.

One thing to note, because the two rails are independent from each other (i.e. separate components), there is a possibility of variance. To achieve the proper distance between the rails (22”), it is up to the installer to position, drill and bolt the rails down in the correct placement.

A Note about OEM Puck Systems

Any time you talk industry-standard 5th wheels, it’s important to bring up OEM puck systems.

As an alternative to the traditional 5th wheel rail setup, truck manufacturers developed the puck system. This is an integrated 5th wheel (or gooseneck) mounting platform built into the truck bed by the manufacturer. It is called “puck” because the mounting points resemble a puck-shape.

The pucks accept compatible 5th wheel and gooseneck equipment, designed specifically for those systems.

OEM Puck System in Truck Bed for 5th Wheel or GooseneckOEM Puck System in Truck Bed for 5th Wheel or Gooseneck

While the puck system does streamline installation and make the overall towing experience easier, it is important to observe that OEM puck systems differ from truck to truck. The Nissan puck system, for example, is different than the Ford puck system. Furthermore, the puck system of one model year may not be the same as that in the next model year, even if the trucks are from the same manufacturer.

The point is, OEM puck systems are not the same as industry-standard rails, and you should carefully check all fitment info before making a purchase, if you choose to go the puck system route.

Measuring Your 5th Wheel Rails & Hitch

Let’s assume you have a pre-existing set of base rails mounted in your truck bed. Perhaps they came with the purchase of the truck or you had them installed previously, and now you’d like to know if they’re industry-standard.

To do this, simply use a measuring tape to find each of the key measurements listed above.

5th Wheel Base Rails Bolted into Truck Bed5th Wheel Base Rails Bolted into Truck Bed
  1. Start with the distance between the slots along the middle of the rail. The two that are closest to each other near the middle should be 10” apart. Be sure to measure center-on-center; that is, from the very center of each slot.
  2. Then, measure the next two slots center-on-center. This distance should be 20-1/2”.
  3. Measure the two outermost slots on each end of the rail. These should be 29” apart center-on-center.
  4. Next, measure the dimensions of the slots. They should be 1/2" x 1-1/4”. Not that some rails come with slightly longer slots, greater than 1-1/4”, but this is still within the tolerance of industry-standard.
  5. Finally, measure the distance between the two rails. Be sure to measure center-on-center from two corresponding slots. The distance should be 22”.

If your rails are not within the parameters of industry-standard, replacement rails may be an option.

Measuring 5th Wheel Legs or a Slider

If you own a 5th wheel hitch and you’re planning to purchase new industry-standard rails to mount the hitch in your truck bed, it is important to know if the hitch will fit.

For 5th wheel legs, you will need the hitch to be fully assembled with the legs, bolted in place as they would be mounted in your truck bed. This will provide an accurate measurement.

For a slider or roller, assembly shouldn’t be necessary as most sliders and rollers are constructed as a single piece.

5th Wheel Hitch Installed in Truck Bed, Wood5th Wheel Hitch Installed in Truck Bed, Wood
  1. Use your measuring tape to measure the distance between two opposing anchoring tabs. Measure from the center of each tab. The distance should be 22”.
  2. Next, turn your measuring tape 90 degrees and measure between two in-line tabs. That distance should be one of three measurements: 10”, 20-1/2” or 29”.
  3. Finally, measure the tabs themselves to ensure they fall within the 1/2" x 1-1/4” tolerance.

If your 5th wheel is not industry-standard, you may wish to upgrade to a new hitch.

Different Types of 5th Wheel Rails

As you begin to shop around for replacement 5th wheel rails, you may notice a few different varieties.

There are different weight capacity options to accommodate different 5th wheels. Some rails have thicker steel and a higher-grade alloy to match the gross trailer weight rating of commercial-class hitches. Some heavy-duty rails are even rated up to as much as 40,000 lbs.

CURT 5th Wheel Gooseneck Hitch on 40K Base RailsCURT 5th Wheel Gooseneck Hitch on 40K Base Rails

Other rails vary in their finish, ranging from gloss to carbide, and black to grey. The finish is mostly a user preference point, as long as it is a quality finish. You may prefer the shiny black look over the flat gray look or vice-versa. It all depends on the color of your truck and 5th wheel hitch. Just remember to choose a set of rails that have a durable powder coat finish to withstand the elements and rigors of the road.

5th Wheel Rail Adapter for Puck System5th Wheel Rail Adapter for Puck System

Another variation you’ll find is in the mounting platform. While traditional 5th wheel rails are designed to be bolted onto a set of underbed brackets, there are also 5th wheel adapter products. For example, the CURT X5 adapter allows you to mount a 5th wheel hitch using your gooseneck ball hole. Likewise, there are 5th wheel adapters for OEM puck systems, equipping the pucks with a set of industry-standard mounting points.

Just remember, as long as the rails themselves meet the key dimensions listed above, they can be considered industry-standard.

Example 5th Wheel Hitch Rails Installation Instructions

When installing new 5th wheel base rails in your truck bed, it is highly recommended that you adhere to industry-standard guidelines. Positioning the rails to match industry standards will only make things easier down the road for any new hitch or other product you buy.

Disclaimer: These photographs, recommendations, and approximations are intended for demonstration purposes only and do not reflect the specifications of any particular tow vehicle, recreational vehicle, or trailer. Always consult the manufacturer’s Owner’s Manual.