By: Carley Sparks
Not all vehicles are created equal when it comes to safe towing
It was a clear, cold morning in January when disaster struck a Calgary, AB, couple hauling their pregnant mare down Highway 2. The Smiths* were towing a two-horse trailer with a 2007 GMC Sierra. As the vehicle approached the Leduc overpass at Highway 39, the hitch started to detach. A mile down the road, it came apart completely. The trailer crashed, killing the horse. Weather conditions and driver error were not factors in the accident; some might question the role the tow vehicle played in it.
The suitability of sports utility vehicles (SUVs) to haul live animals is a hotly-contested topic in transport circles. Livestock handling specialist Jennifer Woods of Blackie, AB, believes SUVs and horse trailers are a recipe for roadside disaster. “I’ve just seen too many wrecks. A good chunk of horse trailer accidents are because people are pulling with under-capacity vehicles,” she maintains.
Kent Sundling, publisher and editor of the online truck review magazine MrTruck.com, says that SUVs can suffice as tow vehicles if properly equipped. “SUVs aren’t my first choice as a tow vehicle, but I do understand the economics. Not everyone can afford a truck and a car,” reasons Sundling.
Clearly, choosing the correct tow vehicle for your trailer is vital to the safety of both horses and handlers. But how do SUVs stack up against pickup trucks?
One primary difference between trucks and SUVs is the design of the chassis, the frame that provides the structural strength of a vehicle. Trucks typically have a “body-on-frame” design wherein the body of the truck sits on a heavy iron frame. “With framed chassis vehicles, the receiver hitch bolts directly to the frame, as do the front and rear axles. The frame is the main strength of it and takes the stress from the trailer directly,” explains Sundling.
Many full-sized SUVs also have these frames and consequently are very strong, he says.
Mid- and small-sized SUVs have a “unibody” design. Originally designed for the Volkswagon Beetle, the unibody chassis is a single-piece construction that forms the body of the vehicle. The axles are mounted to the floor pan on subframes and the frame is made of galvanized steel, making the vehicle lighter and therefore better on gas mileage. “Now, when you’re hooked to a trailer, you don’t have a continuous frame from the front of the SUV to the rear of the SUV; you have little subframes that are only connected to the axle. The rest of that is sheet metal,” says Sundling. The result is a chassis that is not as structurally strong.
The lightness of a unibody vehicle also adversely affects its towing capacity; it cannot tow the same amount of weight as easily as a body-on-frame truck. “Towing capacity is not what the vehicle can move with the trailer behind it,” says Woods. “It is whether the vehicle will be able to control and stop the trailer behind it.”
As a general rule of thumb, she says the weight of the vehicle should exceed that of the trailer. “A trailer that weighs more than the vehicle is asking for a wreck,” says Woods. “If the trailer is swaying or moving, it’ll take your vehicle right off the road — the tail starts wagging the dog. There is also the vehicle side of it. You could take the transmission out of your vehicle very easily [towing with an under-capacity vehicle].”
Odessa Holmes of Equi Balance Horse Trailers in New Zealand agrees, comparing an SUV to a small boy pulling a fully-loaded wheelbarrow. To have the strength to control it, she says the tow vehicle must be heavier than the trailer and weigh “two tons or more for hauling live horses.”
Sundling disagrees with that generalization. “You can’t make a blanket statement that all trucks must be heavier than the trailers. That’s very old school. The new technology is so much better,” he says. “If you look at a semi-tractor trailer, it gets 85,000 lb [of towing capacity]. Well, you may have 30,000 lb on the tractor and 50,000 lb on the trailer; that’s pretty common.”
He says that an SUV that is at least the size of a Ford Explorer and hooked up correctly with an appropriate weight-distributing hitch, quality trailer brakes, and a good brake controller can pull most two-horse trailers under 5,000 lb (fully loaded). “If it’s not equipped right, nothing is safe. It all depends on the equipment.”
Both he and Woods advocate staying under the maximum tow capacity. “On a horse trailer, because you’re not hauling dead weight and they can move around, I would usually go 20 percent off the max,” says Sundling. “So, if it’s 5,000 lb max, I would be closer to 4,000 lb. That’s probably a good estimate with live animals.”
Leveling the load
The chassis of the vehicle also has implications for the type of drive it will have. Body-on-frame trucks and SUVs are available with rear-wheel drive or four-wheel drive (4WD). These typically direct 40% of the power to the front wheels and 60% to the back. With a bumper-pull trailer this is advantageous, as the rear axle of the tow vehicle carries most of the weight and is closer to the point where a trailer articulates, which helps steering.
Most unibody SUVs are front-wheel drive, says Sundling, meaning that about 90% of the power goes to the front wheels. These vehicles fall into the same towing category as front-wheel drive mini-vans. Now when a bumper-pull trailer is hitched, the weight is on the significantly less powerful wheels and could cause skidding.
“Special receiver hitches are required with any front-wheel drive vehicle to transfer weight as far forward as possible to the front driving axles for traction,” says Sundling.
But even with a weight-distributing hitch, the unibody chassis doesn’t transfer weight as effectively as a framed chassis. Sundling says that a sway bar can be added as well. “All this will help you pull level, with weight on all of the axles of the SUV and trailer and less swaying from a bumper-pull trailer.”
It’s worth noting that weight-distributing hitches are often used on rear wheel drive vehicles. “One of the reasons for distributing weight on all the axles is that you want weight on the front of your vehicle so that it doesn’t wander down the road,” says Sundling.
A smoother vehicle isn’t always better
Another important difference between trucks and SUVs is their suspension systems. Most heavy-duty and half-ton trucks have leaf spring suspension, whereas most SUVs have coil spring suspension.
“Leaf springs carry more weight, but coils are a softer ride,” explains Sundling. “They can react faster to a bump, which gives you a better ride, but it also gives you more rear movement. You don’t want extra movement when pulling a trailer.”
The largest SUVs — Chevy Suburban, GMC Yukon XL, and Ford Excursion — are available as three-quarter-ton vehicles and, says Sundling, will pull similarly to three-quarter-ton trucks. The newer models all have leaf springs on the rear axle, which makes them more stable than the smaller SUVs. But, he cautions, even the largest SUVs generally don’t have as long a wheelbase as a truck. The longer the wheelbase, the greater the vehicle’s towing stability when in motion. “Once again, depending on the total weight of your loaded trailer, a weight-distributing hitch might be necessary,” he says.
SUVs with coil spring suspension are less stable in comparison, and some create more extra movement than others. The bigger SUVs have coil springs and are on a “live” axle. “It’s all one piece, like a truck axle. So when the left side goes up, the right side goes down,” says Sundling. “If you have a trailer hitched on the back, the easier the rear of the truck can move, the more the trailer can push you around back there.”
The mid-size and smaller SUVs have independent rear suspension (IRS), similar to a front-wheel drive car. “That is coil spring. too, but instead of having a solid axle, each one is independent. So when the right one goes up, the left one doesn’t get pushed down. Now each tire can do what it wants, but it makes more movement and it amplifies the movement,” says Sundling, which makes it more important on an IRS to have a weight-distributing hitch with sway control.
“It’s not just can it pull it and control it, can that vehicle stop it?” asks Woods. She maintains that total trailer weight is as important as the braking system, if not more so. “When your trailer outweighs your vehicle by 2,000 pounds, no brake is going to stop you.”
Sundling argues that advances in brake technology have improved stopping power. “The newer SUVs have four-wheel disc brakes, which are more powerful than the old drum brakes and can be an advantage slowing a trailer down,” he maintains. As well, both SUVs and trucks typically have electronic stability control (ESC), which detects loss of steering control and automatically applies the brakes to help “steer” the vehicle. According to the National Highway Traffic Safety Administration (NHTSA), one-third of fatal accidents could have been prevented by ESC technology.
Only some trucks, however, come with built-in proportional brakes; SUVs do not. “Normally, brake pressure is applied mostly to the front brakes, so in a hard-braking situation, the rear of the truck lifts up and the brakes will lock the tires. Proportional brakes sense where the load is. If you have a big load on, it will apply brake pressure equally to the front and rear axles, or sometimes even more to the rear axle,” Sundling explains.
Both he and Holmes advocate for electronic brakes on the trailer and a brake controller in your tow vehicle, which detects slowing in the tow vehicle and applies equal pressure to the trailer brakes, so the trailer decelerates at the same rate as the tow vehicle. “The better ones work off the percentage of braking the truck is doing. Those are the safest,” says Sundling.
The final word
With the exception of the Suburban, Woods says SUVs should not be used to pull a trailer. “Period. The ideal tow vehicle is one that is actually built to tow horse trailers, which would be trucks or, if you have to go with an SUV, a Suburban. But I would still be careful with how much you pull with that. That would be an appropriate tow vehicle for a two-horse trailer; you put a four- or six-horse trailer behind you and that vehicle may not have the towing capacity or the suspension to tow a heavier trailer.”
At the same time she cautions that all pickup trucks aren’t created equal either. “You can’t make a blanket statement that trucks are good. You need to make sure the truck is capable of pulling the trailer. Unfortunately, there is not a simple answer for this. You need to do your homework.”
Sundling agrees that heavy-duty trucks are better equipped to tow horses, but says SUVs can be equipped for the task, particularly the heavier body-on-frame designs. “The bottom line is you can safely pull a horse trailer with a properly-equipped SUV when it’s matched properly with a receiver hitch, weight-distributing hitch, engine, transmission and rear axle ratio, within the weight limit capacity set by the manufacturer.”