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Trucks tend to weigh much more than cars. This is due to the sheer size of the truck (when compared to a car), and also due to the materials used and the construction method. A car may have a lightweight aluminum chassis, whereas a truck will use a heavy ladder frame and heavy-duty parts. This is expanded even further when you start thinking about extremely heavy trucks, such as Semi's or flatbeds.
There are three main differences between car lifts and truck lifts:
1. Truck lifts are heavier Truck lifts need to weigh more in order to properly handle the increased weight of the load. They are also secured to the ground better in order to properly distribute the weight from the posts to the ground.
While a car lift can get away with weighing less, a truck lift would almost certainly fail if it was not built to the proper specifications.
2. Truck lifts are designed to lift more The average car lift is designed to lift up to 9,000lbs, whereas most truck lifts are designed to lift in excess of 15,000lbs. The average truck lift is designed to lift 18,000lbs worth of weight.
Once again, this comes down to the fact that trucks weigh more than cars and hence require equipment that is set up to properly handle the difference in weight. Lifting a truck with a car light that is not rated for the weight may result in the lift failing, being unable to lift the truck, or failing in a way that causes damage to the vehicle.
3. Truck lifts are built with different components All of the components of a truck lift are built to handle more stress and lift more weight. Everything from the hydraulics to the lifting posts themselves is designed with an increased weight in mind.
Greater tolerances and capability are instilled in order to ensure safe and reliable operation. Just as a larger vehicle will have larger brakes than a smaller one, a larger truck lift must have more capable equipment to run it.