A tire changer is a machine used to remove tires and mount tires onto wheels. Hydraulically-operated, a tire changer uses compressed air and hydraulic fluid to compress a tire, breaking it free of its seal to the wheel. Once the tire's bead has been broken, a tire tool is used to spin between the tire and the wheel, literally peeling the tire off of the wheel. With the old tire removed, it is time to place a new tire on the wheel and use the tire tool to squeeze the tire over the wheel's outer lip and into position on the wheel. The tire is then inflated, sealing it to the wheel's bead, and the air pressure is monitored by watching an air pressure gauge affixed to the tire changer.
Prior to the invention of the tire changer, tires were changed by hand. This was accomplished by breaking the tire's bead loose through the process of pounding it with a hammer, eventually driving the bead down and out of place on the wheel. With the bead broken, two flat iron bars were inserted between the tire and the wheel and the tire was then slowly worked up and over the wheel's lip. This was a very labor-intensive job and could take hours to change a single tire.
The earliest version of the tire changer was a model that was completely powered by hand. The basic design was very similar to the tire changer that came after; however, all of the machine's actions were accomplished by a person pulling and pushing the attachments by hand. Instead of having electric motors and compressed air to operate the machine, a mechanic simply slid the attachment into position and then used his strength and determination to operate the tire changer.
Many times, the mechanic using the earlier machines would resort back to using a hammer out of frustration over not being strong enough to push the tire changer attachment by hand. This technique led to the nickname for a tire-changing worker to be called a tire buster and the act of changing a tire to be known as busting a tire. The inclusion of the electric hydraulic system accompanied by the use of compressed air to operate a tire changer made the job much less physical.
The modern tire shop has several tire-changing machines tailored for special duties. Machines for steel and aluminum wheels, motorcycle tires and even huge semi-tire changing machines are common. The effectiveness of the modern machines makes changing tires a minimal-effort job.