Matching truck to trailer involves many factors that must be considered. In an ideal world, someone who wants to have a truck and towable RV will find just the right RV and then buy a truck that is capable of safely towing it. Unfortunately, the world isn’t perfect, and many folks have a truck and try to find a trailer to pull or vice versa. In this page we will lay out all the considerations to help you make a choice that will be both safe and effective. Some of this is fairly complex. I wish I could make it easier, but these are things you should understand.
Unfortunately, many folks rely on information they get from a salesman at an RV dealer or truck dealer. Salesmen are in business to make money by selling you a vehicle or RV. They are educated on how to sell. They are not educated about RV safety or all that goes into making a smart decision. They just don’t know much. Please base your buy decisions on your knowledge, not that of a salesman.
According to the RV Safety and Education Foundation(RVSEF), who weighs thousands of rigs every year, 57% of all RVs on the road exceed one or more weight safety ratings. Additionally, the following exceed at least one rating:
- 60% of all tow vehicles
- 51% of all travel trailers
- 55% of all 5th wheel trailers
- 50% of all trailers exceed the GVWR
What we want to accomplish is to familiarize you with the terms you need to know as well as other issues so you can make an informed decision on matching truck to trailer as well as what will work safely and what will not.
Specifications for Matching Truck to Trailer
There are several universal terms we will use throughout this discussion that you should know thoroughly. They are:
GVWR (Gross Vehicle Weight Rating) — how much weight a vehicle is designed to carry, set by the manufacturer. The GVWR is typically listed on a data plate near the driver’s doorframe, and includes the net weight of the vehicle, plus the weight of driver, passengers, fuel, cargo and any additional accessories. (Driver and passengers are figured at 150 pounds each)
GCWR (Gross Combination Weight Rating) – is the maximum allowable weight of the combination of tow vehicle and trailer/ fifth-wheel, or motor home and dinghy. It includes the weight of the vehicle, trailer/fifth-wheel (or dinghy), cargo, driver, passengers and a full load of fluids (fresh water, propane, fuel, etc.).
GTWR (Gross Trailer Weight Rating) – Maximum allowable weight of a trailer, fully loaded with cargo and fluids.
GAWR (Gross Axle Weight Rating) – The manufacturer’s rating for the maximum allowable weight that an axle assembly is designed to carry. GAWR applies to tow vehicle, trailer, and fifth-wheel and motor home axles.
MLTW (Maximum Loaded Trailer Weight) The maximum weight that a tow vehicle is rated to tow. Hitch Ratings: The hitch on a tow vehicle will have two distinct and important ratings. The TOW rating, which defines the maximum weight of a trailer in tow. The VERTICAL or TONGUE rating, which defines the maximum vertical hitch load that the trailer can impart to the tow vehicle.
There are also some other ratings that concern dry weight, which is how the trailer comes off the factory production line. We know no body will arrive at a campground with a dry, unloaded rig, so we discount those ratings.
The Truck
Our next step in matching truck to trailer is to look at the specifications from the truck manufacturers. This can be quite confusing as some do not use the same terms. Most folks will want to know it their truck will tow a particular trailer and that’s where the Maximum Loaded Trailer Weight rating comes in.
First you must know the loaded weight of your truck. The only way to find that out is to put your truck with the load you would use on a scale with full fuel and all passengers. You might want to drive the truck on the scale, get the total weight, and then drive the front axle off the scale to get the rear axle weight.
Then you subtract the total truck weight from the Gross Combined Vehicle Weight (GCVW). The answer is the total the trailer can weigh to be towed safely.
The Trailer
Now the trailer part of matching trucks to trailers. If you already have a trailer, hook it up and drive it on the scale with the truck off the scale. Next drive forward till the front trailer axle is off the scale. Repeat if there is a third axle. If the total truck and trailer weights exceed the GCVW, you need to decide what to remove to get to a safe total weight.
Every trailer has a tag or plate that shows either the tongue weight if a Travel Trailer or the pin weight if a fifth wheel trailer. It is a dry weight. Earlier I listed a specification of GAWR or gross axle weight rating. You have the weight of the rear axle with trailer from the scale. If you exceed the GAWR, you must remove weight from the front of the trailer. As long as you are not over the combined vehicle weight rating, you can move things around towards the back. Now it starts to get complicated. Remember I had you get the weight of each trailer axle? You want them to be as close as possible to equal to avoid uneven tire wear.
The Weakest Link
The weight ratings for trucks and trailers are there because the manufacturer uses components that can handle the specified weight. Trailer axles have weight ratings. If you have 2 7000 pound axles on your trailer, that is 14000 pounds. You don’t want to load it to 16000. That makes the axle a weak link. Trucks rear springs have a weight rating. If exceeded, handling will be affected and the springs can deteriorate. Both truck and trailer brakes are weight rated. When you are overweight, the brakes heat up and will fade. Your stopping distance will increase dangerously. Tires also have weight ratings. If you are loaded beyond the maximum tire weight rating, you are looking at a blowout. Selection and proper installation of a hitch that is rated properly is an essential part of matching truck to trailer. The hitch must have a tow rating at least equal to the GVWR of the trailer. The vertical rating of the hitch must be at least equal to the vertical load imparted by the trailer to the tow vehicle.
I mentioned weighing your rig at a weigh station or truck stop. The very best way to do this is to have all tire positions weighed. The aforementioned RVSEF does this as well as the Escapees RV club SmartWeigh program.
http://www.escapees.com/knowledge/smartweigh/program-info
Scales at each wheel position
Changing Weight Ratings
Many owners make modifications to their rigs to improve the load capacities or performance with components certified by the manufacturer. They are trying to force matching truck to trailer. Air lift systems, helper springs, higher capacity wheels and tires are some things owners add to their rigs to improve the vehicle towing or load capacity, or performance. Unfortunately, a set of stronger springs will not affect the capacity of the rear axle.
Those owners automatically assume legal responsibility for all modifications made to their rigs and they will assume the risk. An insurance company may well deny a claim if they determine that unofficial changes have been made.
There’s a Video for That
The RV Safety and Education Foundation(RVSEF) has developed a video called Matching Trucks to Trailers. Here is a link:
http://rvsafety.com/rv-education/matching-trucks-to-trailers
There’s an App for That
Much of the research for this matching truck to trailer was with material from the folks at http://www.fifthwheelst.com Their website is a treasure trove of safety information for those towing trailers. They have developed the “5th Wheel ST” fifth wheel and Gooseneck Towing Weight Calculator and Safety Report as an App for android and IOS devices. You simply enter information from data plates and scale readings and the readout will tell you 7 points indicating the safety margin or overload conditions. This could well be the best $1.99 you will ever spend.
Check it out at: http://fifthwheelst.info/