Vehicle Control

Oct 16th, 2013 | By | Category: From our latest issue

Editor’s Note: this online article is a more in-depth version of the article “Vehicle Control” that appeared in the Tow Times October issue.

The formula ½ FAW x WB/ OH is often used to determine the lift weight capacity of a tow truck. Under this formula, the front wheels of the truck are weighed to determine the front axle weight (FAW). Then the distance from the middle of the front axle to the middle of the rear axle is measured to determine the wheel base (WB). Measuring from the middle of the rear axle to the maximum extension of the tow sling gives the final measurement, which is “overhang” (OH).

An example for this formula is a truck with a front axle weight of 3,800 lbs., a wheelbase of 131” and an overhang of 96”. Thirty-eight hundred pounds divided by 2 equals 1,900 lbs. x 131 to equal 248,900 which divided by 96 produces the figure of 2,592 lbs., the theoretical safe lift capacity for this truck. It is generally accepted in the towing industry that as long as half of the tow truck’s empty weight is preserved during towing, that the tow is safe.

The original source and any research behind the formula are unknown so it should not be accepted as fact. It does not consider the total weight or load capacity of the tow truck, coefficient of friction of the tires and pavement (an extremely important factor), road conditions, whether the truck has anti-lock brakes or traction control, or any other mechanical differences between one tow truck or another. Stay well under these ratings and make sure the total weight of a towed vehicle does not exceed the gross vehicle rating of the towing mechanism, the truck chassis or the tires. If the truck does not feel like it is stable during towing, does not stop easily, or steering is difficult, you should reduce the size of towed vehicles until you find a load weight that feels safe. Under no circumstances, should any axle carry more of a load than that specified by the manufacturer.

It is important to build into a new truck features that will improve handling and control and this is best done when considering the purchase of a new truck. Ford offers “Engine Only Traction Control” (which uses the engine to help control wheel spin), “Electronic Locking Rear Differential, and “Tow Haul Mode” (provides engine exhaust braking). General Motors offers “Tow Haul Mode” for steep grades, “Low Traction Mode” for slippery roads, “Stabilitrac” (helps directional control), and locking rear axle to give assistance if the vehicle is stuck on soft ground. “Cruise Grade Braking” assists when going downhill. Ford and General Motors both offer anti-lock brakes, which are essential on any tow truck. These modern systems assist in vehicle handling during difficult situations and getting sales brochures from dealers can help you design the best truck for your needs.

Other measures that directly affect tow truck handling are driving speed and maintaining safe distances behind other vehicles. Towing with the light end of a vehicle in a wheel-lift with the towed vehicle pulled close to the tailboard of the truck will increase the weight maintained on the front tires.

When towing, turn off your radio so you can hear noises, particularly changes in noise. Pay attention to sounds of items breaking, tire noise, or whining or scraping noises from the towed vehicle (as well as your own). Be alert to odors such as dragging brakes or smoking tires. Maintain a following distance of at least four seconds when behind another vehicle if your truck is not loaded and at least six seconds when you have a vehicle in tow. Increase this distance when weather conditions are poor.

When possible, stay in the right lane so you can steer onto the road shoulder in an emergency such as when another vehicle drifts into your lane. Releasing your gas pedal well before stopping or slowing allows the engine to help reduce speed and reduce heating of your brake pads. Most tow truck manufacturers suggest driving at or below 50 miles per hour when towing and this is mandated by all tow dolly manufacturers. At higher speeds during darkness, by the time your headlights allow you to see a hazard ahead, you may not have time to react to avoid the hazard. This is known as “overdriving your headlights. The headlamps of a tow truck aim high when a vehicle is lifted on the rear of the truck and visibility is reduced.

In rain, water will be forced between your tires and the pavement and cause hydroplaning of your tires and greatly increase braking distance and reduce steering capability.

Always account for everyone in the area of your truck when backing to hook up a vehicle or when you start pulling away with it. Failure to do this has resulted in tow trucks running over children or other people who are not alert to tow truck movement.

Keep personal items in a satchel, glove box, or other storage bin so these items cannot get in your way or distract you during an emergency. Nothing should be stored under the driver’s seat as these items can easily slide under the brake pedal or strike the gas pedal during an emergency.

Tow company owners and drivers should take advantage of the National Driver Certification Program Level 1 offered by the Towing and Recovery Association of America (1-800-958-3781) and the excellent Coaching for One Tow Truck Operator program offered by Coaching Systems (1-800-354-9099). Both certification programs offer excellent training in towing safety.