Tow truck operators carry specific kinds of chains for doing what they do. Along with those chains are hooks, car hauling straps, and other equipment that operators need to safely rescue and transport disabled vehicles. One thing is for sure though, not all chains are suitable for towing. Tow operators have to have either G70 or G80 chains.
The ‘G’ in G70 chain stands for ‘grade’. Industrial chains made of steel are graded according to their tensile strength. The higher the grade, the stronger the chain. A G30 chain is the weakest of the options. This is usually a general-purpose chain made for light industrial and agricultural use. The strongest is grade 100. This kind of chain is made with a strong steel alloy capable of handling heavy loads during overhead lifting.
We explain all of this to say that tow operators cannot take chances with their chains. Any chains purchased with the intent of using them in vehicle recovery have to meet minimum standards for strength. Using inadequate chains is both unsafe and illegal.
Tensile Strength and WLL
There are two factors to consider when using chains to tow or lift overhead. The first is tensile strength, a measurement of how much force an object can withstand before breaking. That is where the grading comes in. A higher-grade chain can handle more force than a lower grade chain.
A G70 grade is capable of handling 700 newtons per square millimeter. It might elongate somewhat during towing, but it is unlikely to be compromised under normal circumstances. G70 chain has a strong enough tensile strength to withstand the punishment delivered by most towing operations. Having said that, it is not strong enough for safe overhead lifting.
The second factor to consider is working load limit (WLL). Although this measurement is similar to tensile strength, it is not quite the same thing. Working load limit measures how much work a chain can actually do before breaking. If a tow truck is towing a car in a cradle, with the rear wheels still on the ground, the load being carried is less because the ground is supporting some of the car’s weight. If that same tow truck were to lift the car straight off the ground, the load would be greater.
This suggests that the same chain may be appropriate for one operation but not another. So tow truck operators have to understand working load limits in relation to the kind of stress each particular recovery will have on the chain being used. Attempting recovery operations without understanding tensile strength and WLL is dangerous.
Towing with a Passenger Car
With just this little bit of information it should become apparent just how dangerous it is to use ropes or chains to tow a disabled vehicle using a passenger car. Yet we see it all the time. You might see a four-door sedan towing a disabled SUV down city streets using nothing more than a piece of rope the driver grabbed from the garage.
Such dangerous towing is an open invitation to disaster. The driver of the tow vehicle can easily lose control; the person in the towed vehicle behind could slam into the vehicle in front by not braking quickly enough; ropes and chains can snap, etc. There is just no good way to tow a disabled vehicle without a purpose-built truck.
No, not all chains are suitable for towing. You need a steel G70 chain at minimum. If you have any plans to lift vehicles rather than simply towing them, you will need either G80 or G100.