Towing Basics
Tow trucks have been around for almost as long as there have been cars on the road. Over the decades, the methods for removing damaged or illegally parked vehicles have evolved substantially.
Slings, chains, and hooks are used much less often than in the old days
Initially, tow trucks used chains and hooks wrapped around the car's axle or frame rail to lift it. Some tow truck operators still use this technique in certain conditions. This method is quite secure, but takes a significant amount of time and effort to get the vehicle into position. In its time, this was a fine enough way to secure a vehicle, but with modern vehicle construction there is a great risk of significant damage to vehicle bumpers, along with heavy strains put onto suspension components or the vehicle's frame.
Come forward a few decades, and tow trucks moved to a design that lifts the vehicle by a pair of its wheels, known as the 'wheel lift'. The early versions of this design were a slow process, involving manually removing and re-setting heavy-duty steel pins that held the 'L-arms' of the cradle in place, and relied on the truck's winch cable for lifting power. Surprisingly, there are still some companies using tow trucks like this to this day.
The hydraulic-powered wheel lift
Modern tow trucks use a hydraulic-powered version of the wheel lift mechanism. A large steel arm is lowered level with the ground in front of the vehicle, the truck's cradle hydraulically extended beneath it, then a separate pair of hydraulically-controlled arms are brought around a pair of the vehicle's wheels. Raise the truck's arm, secure the vehicle to the truck with some soft ratcheting straps on the tyres, and you're ready to transport a vehicle.
Combined with a towing dolly - a specialised set of wheels that are assembled using extendable bars between them to raise the vehicle's other set of wheels - vehicles that would previously need a flatbed tow truck can be safely and quickly moved with a wheel lift.
With the strength of hydraulics, and the versatility of individually-controlled components, these wheel lift tow trucks can tackle the most complex jobs in towing, without putting any strain on the vehicle's parts beyond what is experienced under normal driving conditions.
