By Matthew Barnes
Looking to purchase a travel trailer? Getting a new boat to take friends and family to the lake? Need an excavator to dig a foundation for a shed? If you need to tow a trailer, it's a good idea to make sure your tow vehicle can handle the load. How can you figure out the amount a vehicle can safely tow? Follow this guide.
First, here's a primer for the terminology involved in towing.
- Gross vehicle weight rating: The GVWR is the maximum amount a vehicle can safely weigh when fully loaded.
- Gross axle weight rating: The GAWR is the maximum weight that can be safely placed on a single axle of a vehicle.
- Gross combined weight rating: The GCWR is the maximum allowable weight for the tow vehicle, the passengers and cargo in the tow vehicle, and the trailer and cargo in the trailer.
Know How Much You Can Tow
The GVWR and GAWR are easy to find. These numbers are printed on a tag on the driver's doorjamb (see photo below). Knowing these numbers can help determine how much cargo a vehicle can hold and what tongue weight can be placed on the vehicle. After checking the GAWR and GVWR, look for the tow vehicle's GCWR in the owner's manual. You can find the GCWR for newer vehicles on manufacturer websites as well. Ratings will vary significantly depending on the vehicle's engine, transmission, cab configuration, bed configuration and axle ratio.
Most trailers have a tag on the driver's side near the front that lists the GAWR for each axle and the total GVWR. As seen on the door tag above and in the three photos below, be aware that the sum of the GAWR for all the axles may not be the same as the GVWR. In the first photo below, we see a trailer with three 7,000-pound GAWR axles with a GVWR of 21,000 pounds. In the second photo, the trailer has two 7,000-pound GAWR axles with a GVWR of 15,000 pounds. And in the third photo, the trailer has three 7,000-pound axles with a GVWR of 17,000 pounds.
A variety of trailer tags
Once those numbers have been found, check the receiver on the tow vehicle to be sure that it is rated to handle the loads that will be towed. Be aware that some vehicles have different numbers for weight carry and weight distribution. Be sure to check the rating on the trailer hitch or ball mount as well. The lowest-rated piece of towing equipment will determine the most weight that can safely be towed.
Now that all the information has been gathered, it's time to load up and hit the scales. First, measure the tongue weight. The desired trailer tongue weight will vary depending on the type of connection between the tow vehicle and trailer. Conventional trailers, also known as bumper-pull, should have a tongue weight that is 10 to 15 percent of the total trailer weight. Both gooseneck and fifth-wheel trailers should be between 15 and 30 percent. This will be covered in-depth in a future story.
How to Calculate Tongue Weight
Next, with the trailer connected to the tow vehicle, measure the weight on each axle of the tow vehicle to get the gross axle weight for each axle and the gross vehicle weight. Then, weigh each axle on the trailer with it connected to the tow vehicle to get the GAW for each axle and the GVW of the trailer. Add together the GAW of all axles on the tow vehicle and the trailer to get the gross combined weight of the tow vehicle and trailer. Be sure these weights do not exceed the ratings for the tow vehicle, trailer or towing connections.
If the GCW is not over the GCWR, but the rear GAW of the tow vehicle exceeds its GAWR, try redistributing cargo in the vehicle. If the trailer is far enough below its GVWR to handle the extra weight in the tow vehicle, consider shifting the extra weight to the trailer. However, remember that the type of trailer being towed determines how much of the total trailer weight can be placed on the tongue. And that can be as little as 10 percent of the total trailer weight. That means that any weight moved from the tow vehicle to the trailer can reduce the weight on the tow vehicle by as much as 90 percent of the weight moved. This may be enough to keep the loads below the weight ratings.
Once all of that is done, it's time to hit the road. While this might seem like a lot of work, once you gain experience preparation time will decrease. The more you tow, the more you get a feel for when your truck or trailer are improperly loaded.
State Towing Regulations
State laws vary, so it is always a good idea to look up your local state laws and the laws for any state in which you will be towing. Doing this will ensure that you have proper licensing and understand towing laws. Some states have different speed limits for vehicles that are towing. Other states require a Class A license for noncommercial use when the GCWR exceeds 26,000 pounds. If the state you live in that doesn't require a Class A license, then you can travel through other states without needing a Class A license. For commercial towing, federal law mandates that all vehicles with more than a 10,000-pound GCWR must be properly licensed and that the driver have a medical card. Federal law also mandates that a commercial driver's license is required to drive a commercial vehicle with a GCWR greater than 26,000 pounds.
It may take some time and a little bit of math to determine how much a vehicle can safely tow, but it only needs to be figured out once. With that knowledge, you can determine which trailers a vehicle can pull. While it's not plausible to weigh every trailer you tow, it's a good idea to measure the tongue weight and trailer weight of trailers you purchase or will be towing regularly.
Cars.com photos by Matthew Barnes