No doubt, you’ve seen both types of these jacks around. So what exactly are the differences? Which is better? Do both of them have their purposes for use?
A scissor car jack (aka a screw jack by some) consists of diagonal metal elements connected in a diamond shape with hinges and a screw connecting the opposite sides of the diamond. By turning the screw using a spanner, a raising or lowering effect is achieved. The scissor jack comes as standard equipment for most vehicles, for when you need to change a tire. However, it’s notable that trucks and high clearance vehicles come with different types of jacks due to their weight and height of chassis or both. This particular type of jack works by converting rotational motion into linear, since the turning of the screw causes expansion or contracting of the diamond shape, which then translates to an upward force or downward, when the jack is placed between solid ground and vehicle chassis.
Floor jacks on the other hand are a type of hydraulic jack. Hydraulics involves a set of two pistons, one small and another large, work is done on the small cylinder (pushing) and this force is transmitted to the larger one via hydraulic fluid, where mechanical advantage is gained and the output piston produces a great force. Hydraulic jacks use this principle, but instead of direct contact between the pistons, the small piston pumps oil into the chamber of the bigger one via a system of valves. In the floor jack, the piston pushes a crank which connects to a lift pad, which is then lifted. Floor jacks have large lifting capacities compared to screw jacks; up to 10 tons or more and also have a higher max lift height. See also: How a Floor Jack Works
Floor jacks seem to have an obvious upper hand when compared to scissor jacks directly, but each has its advantages and disadvantages. Screw jacks have simple construction, making them quite compact. They also fold for storage which greatly reduces their size making them easy to fit out of the way in the trunk. Floor jacks on the other hand have sturdier construction which amounts to their large size and additional weight. Because of that weight, they have wheels, so don’t imagine carrying one around in your car unless it’s a lightweight aluminum model.
Scissor jacks are much cheaper compared to hydraulic jacks, due to some obvious reasons like lifting capacity and build type. So if money is an issue you may consider sticking with a scissor jack until your budget allows you to upgrade. Screw jacks also require minimal maintenance which entails simply greasing the screw. Floor jacks, may require a bit more maintenance due to the presence of hydraulics which have to be checked for leaks so the cost of maintenance may be higher. For instance, bleeding your hydraulic jack may be necessary but the process is pretty simple.
On the other end, scissor jacks support less weight and can wear out much faster over time. This may be a major drawback if you like to do auto maintenance and repair at home. Also the diamond shape, while a strong shape, may be more prone to failure when under extreme loads. So you may have to consider what you’re lifting to avoid a catastrophe. The use of jack stands with scissor jacks is difficult do to the fact that the jack’s maximum lift height is often not high enough to allow enough clearance for jack stands to be slid under the vehicle. Therefore, we do not recommend using a scissor jack for any type of general maintenance work.
If you feel the only time you’ll ever need to lift up your car is to change a flat tire, a scissor jack is probably all you’ll ever need. For anyone else, the small investment in a hydraulic floor jack is absolutely worth it.