Tow Vehicle, Hitch and Trailer Considerations
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From: Davie, FL
There has been some discussion about towing your S2000 to the track, and one racing adage is “the most dangerous part of a race weekend is the tow to and from the event.” Because of these real concerns I wanted to contribute some information that I have compiled concerning tow vehicle selection.
Tow Vehicles:
In general, buy the heaviest, longest tow vehicle that you can. One guideline is that the tow vehicle should weigh as much (or more) than the loaded trailer. However, this is often not practical or even possible when you’re pulling a lot of weight, and many people try to make do with multi-purpose, undersized vehicles. This can create dangerous situations when trying to control the rig during emergency maneuvering, when large vehicles pass, or in crosswinds. Another guideline is that vehicles with longer wheelbases tend to be more stable when towing. This gives the rig greater stability since side loads at the rear of the vehicle have less effect, but turning radius and ease of parking/storage is compromised. For the ultimate in rear stability, dual rear wheels (DRW) give a very stable platform with higher weight handling capabilities compared to single rear wheel (SRW) configurations.
Hitches:
The simplest hitch is a ball mounted to the bumper. While this may work for the lightest of trailers, even heavy-duty trucks have a 5,000 pound weight limit on this design. A better solution is a frame-mounted 2.25” receiver hitch that has a sufficient rating for your towing (most are rated to 10,000 or 12,500 pounds. Add to that a draw bar and ball and you have the next most basic setup.
For trailers heavier than about 5,000 pounds, it becomes advantageous to add a weight distributing system. This transfers some of the trailer tongue weight off the rear of the tow vehicle to the front and reduces bouncing and sway.
Sophisticated hitches like the Henesley-Arrow are worth considering for the ultimate in sway and load control.
Goose-neck / Fifth Wheel designs, where a ball or plate is mounted in the bed of the truck, offer additional advantages such as increased weight handling, stability, and maneuverability, but require the open bed of a pickup truck for implementation.
Trailers:
When choosing trailers, you need to consider trailer weight, capacity and frontal area. Just like the tow vehicle, make sure that the trailer can comfortably carry the load you expect. An S2000 plus an extra set of wheels, tools and spares will easily weigh about 3,500 pounds. That’s well within the capacity of most any car hauler, but check to make sure. Frontal area is also important to consider, since even light trailers may create a large amount of extra drag at higher speeds if they are tall, especially when being towed by a smaller vehicle. For car hauling, open trailers tend to be the lightest and lowest, while closed trailers give greater security and protection to your equipment at the expense of weight and aerodynamic drag.
Tires:
Be careful with used equipment, as replacement tires may not have the same rating as the original ones. Since some vehicles and/or trailers use Light Truck (LT) tires, they may need to be filled with more air than you might expect (up to 90 psi) to carry the load properly. More typically this is in the 40-50psi range, check the pressures recommended by the manufacturer, or if that information in not available, the maximum pressures that are molded into the tire sidewall. Even slightly under inflated tires have drastically reduced load capacities.
Trailer Towing:
Pay little attention to the trailer weight ratings that are published by the manufacturer. They should be considered to be the maximum values under the most ideal situations and are rarely relevant to real-world situations. They tend to be very optimistic by not including optional equipment and weights of passengers, equipment, and fuel loaded into the tow vehicle in their calculations.
So what REALLY determines the maximum capacity of my trailer and tow vehicle? Do the following calculations for both the tow vehicle and trailer to find out for yourself!
Let’s start from the ground up.
1) Make sure that the tow vehicle tires can carry the expected load. All DOT legal tires have their maximum load ratings molded into the sidewall. Add up the ratings of all the tires and that gives you one total.
2) Next, check the load rating of each tow vehicle axle. Add them together to give you another total.
3) Last, check the manufacturers plate, usually affixed to inside the doorsill or the frame near the front of the trailer for the Gross Vehicle Weight Rating (GVWR).
The maximum capacity of each vehicle is the lowest of these numbers, usually the GVWR.
For example, the S2000 is rated to carry occupants and luggage totaling no more than 400 pounds – did you know that?
As another more relevant example, my wife’s Ford F250 has LT 265/75R16 tires, rated at 3415 pounds each at 80 psi. for a total capacity of 13,660 pounds. The Front Gross Axle Weight Rating (FGAWR) is 4,850 pounds and Rear Gross Axle Weight Rating (RGAWR) is 6,084 pounds for a sum of 10,934 pounds. However, the Gross Vehicle Weight Rating (GVWR) is “only” 8,800 pounds. Therefore, the total weight capacity of the truck is 8,800 pounds, and I am confident that each axle and tire can support this load. Since the truck weighs about 6,500 pounds, that leaves 2,300 pounds as payload. That may seem to be a lot, but let’s see how quickly that gets used up.
A full tank of fuel weighs about 175 pounds, two people average 325 pounds, plus all of our personal gear and stuff is another 500 pounds or so and we’re now up to 1,000 pounds of cargo and a tow vehicle gross weight of 7,500 pounds. This leaves about 1,300 pounds in reserve to handle the trailer tongue weight.
According to the Ford trailer-towing guide, the F250 Supercab SRW 4x2 with automatic transmission and the 6.0L diesel can tow 12,500 pounds with a weight-distributing hitch. Since you want 10-15% of the trailer weight on the ball, that maximum trailer weight should put a maximum of 1,875 pounds on the tow vehicle. Since there is only 1,300 pounds available, I would be overloading the vehicle by 575 pounds, even though the trailer weight is within Ford’s guidelines. A quick calculation shows that I would need to limit the trailer weight to 8,700 pounds in order to have the maximum GVW on the truck. As another cross check, I’d also go back and look at the RGAWR and make sure I don’t exceed 6,084 pounds there. It’s a helpful exercise to take your loaded rig to an RV or truck weighing facility and make sure that you are within all appropriate weight limits.
This same procedure should be followed to make sure the trailer weight rating is not exceeded. For all but the lightest of trailers, the maximum loaded weights can be found on a plate mounted near the front.
Here is one website links used as references in this posting and for continued reading on the subject:
http://www.sherline.com/lmbook.htm
There are many interesting discussions in the towing forum at thedieselstop.com .
Tow Vehicles:
In general, buy the heaviest, longest tow vehicle that you can. One guideline is that the tow vehicle should weigh as much (or more) than the loaded trailer. However, this is often not practical or even possible when you’re pulling a lot of weight, and many people try to make do with multi-purpose, undersized vehicles. This can create dangerous situations when trying to control the rig during emergency maneuvering, when large vehicles pass, or in crosswinds. Another guideline is that vehicles with longer wheelbases tend to be more stable when towing. This gives the rig greater stability since side loads at the rear of the vehicle have less effect, but turning radius and ease of parking/storage is compromised. For the ultimate in rear stability, dual rear wheels (DRW) give a very stable platform with higher weight handling capabilities compared to single rear wheel (SRW) configurations.
Hitches:
The simplest hitch is a ball mounted to the bumper. While this may work for the lightest of trailers, even heavy-duty trucks have a 5,000 pound weight limit on this design. A better solution is a frame-mounted 2.25” receiver hitch that has a sufficient rating for your towing (most are rated to 10,000 or 12,500 pounds. Add to that a draw bar and ball and you have the next most basic setup.
For trailers heavier than about 5,000 pounds, it becomes advantageous to add a weight distributing system. This transfers some of the trailer tongue weight off the rear of the tow vehicle to the front and reduces bouncing and sway.
Sophisticated hitches like the Henesley-Arrow are worth considering for the ultimate in sway and load control.
Goose-neck / Fifth Wheel designs, where a ball or plate is mounted in the bed of the truck, offer additional advantages such as increased weight handling, stability, and maneuverability, but require the open bed of a pickup truck for implementation.
Trailers:
When choosing trailers, you need to consider trailer weight, capacity and frontal area. Just like the tow vehicle, make sure that the trailer can comfortably carry the load you expect. An S2000 plus an extra set of wheels, tools and spares will easily weigh about 3,500 pounds. That’s well within the capacity of most any car hauler, but check to make sure. Frontal area is also important to consider, since even light trailers may create a large amount of extra drag at higher speeds if they are tall, especially when being towed by a smaller vehicle. For car hauling, open trailers tend to be the lightest and lowest, while closed trailers give greater security and protection to your equipment at the expense of weight and aerodynamic drag.
Tires:
Be careful with used equipment, as replacement tires may not have the same rating as the original ones. Since some vehicles and/or trailers use Light Truck (LT) tires, they may need to be filled with more air than you might expect (up to 90 psi) to carry the load properly. More typically this is in the 40-50psi range, check the pressures recommended by the manufacturer, or if that information in not available, the maximum pressures that are molded into the tire sidewall. Even slightly under inflated tires have drastically reduced load capacities.
Trailer Towing:
Pay little attention to the trailer weight ratings that are published by the manufacturer. They should be considered to be the maximum values under the most ideal situations and are rarely relevant to real-world situations. They tend to be very optimistic by not including optional equipment and weights of passengers, equipment, and fuel loaded into the tow vehicle in their calculations.
So what REALLY determines the maximum capacity of my trailer and tow vehicle? Do the following calculations for both the tow vehicle and trailer to find out for yourself!
Let’s start from the ground up.
1) Make sure that the tow vehicle tires can carry the expected load. All DOT legal tires have their maximum load ratings molded into the sidewall. Add up the ratings of all the tires and that gives you one total.
2) Next, check the load rating of each tow vehicle axle. Add them together to give you another total.
3) Last, check the manufacturers plate, usually affixed to inside the doorsill or the frame near the front of the trailer for the Gross Vehicle Weight Rating (GVWR).
The maximum capacity of each vehicle is the lowest of these numbers, usually the GVWR.
For example, the S2000 is rated to carry occupants and luggage totaling no more than 400 pounds – did you know that?
As another more relevant example, my wife’s Ford F250 has LT 265/75R16 tires, rated at 3415 pounds each at 80 psi. for a total capacity of 13,660 pounds. The Front Gross Axle Weight Rating (FGAWR) is 4,850 pounds and Rear Gross Axle Weight Rating (RGAWR) is 6,084 pounds for a sum of 10,934 pounds. However, the Gross Vehicle Weight Rating (GVWR) is “only” 8,800 pounds. Therefore, the total weight capacity of the truck is 8,800 pounds, and I am confident that each axle and tire can support this load. Since the truck weighs about 6,500 pounds, that leaves 2,300 pounds as payload. That may seem to be a lot, but let’s see how quickly that gets used up.
A full tank of fuel weighs about 175 pounds, two people average 325 pounds, plus all of our personal gear and stuff is another 500 pounds or so and we’re now up to 1,000 pounds of cargo and a tow vehicle gross weight of 7,500 pounds. This leaves about 1,300 pounds in reserve to handle the trailer tongue weight.
According to the Ford trailer-towing guide, the F250 Supercab SRW 4x2 with automatic transmission and the 6.0L diesel can tow 12,500 pounds with a weight-distributing hitch. Since you want 10-15% of the trailer weight on the ball, that maximum trailer weight should put a maximum of 1,875 pounds on the tow vehicle. Since there is only 1,300 pounds available, I would be overloading the vehicle by 575 pounds, even though the trailer weight is within Ford’s guidelines. A quick calculation shows that I would need to limit the trailer weight to 8,700 pounds in order to have the maximum GVW on the truck. As another cross check, I’d also go back and look at the RGAWR and make sure I don’t exceed 6,084 pounds there. It’s a helpful exercise to take your loaded rig to an RV or truck weighing facility and make sure that you are within all appropriate weight limits.
This same procedure should be followed to make sure the trailer weight rating is not exceeded. For all but the lightest of trailers, the maximum loaded weights can be found on a plate mounted near the front.
Here is one website links used as references in this posting and for continued reading on the subject:
http://www.sherline.com/lmbook.htm
There are many interesting discussions in the towing forum at thedieselstop.com .
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