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A bead breaker is a tool used for separating tires from rims. The inner-most diameter of the tire that interfaces with a wheel is called the Tire Bead. The tire bead is a thicker section of rubber, and is reinforced with braided steel cable, called the Bead Bundle. The inner-most surface of the tire bead creates the air seal between the tire and rim on a radial-ply tire and a bias-ply tire. Often, the bead can become frozen to the rim after rusting or corrosion occurs, requiring the use of a bead breaker in order to be removed.
A need was experienced by avid 4x4 enthusiasts and overland travelers for a simple tool to effectively and efficiently remove the tire from the rim of a wheel, in cases where a tire requires repairs to the inside. On ATV's, as well as motorcycles, passenger vehicles, trucks, many industrial and offroad vehicles, as well as light aircraft have an additional feature on the rim called the Bead Retainer. The bead retainer is a bump like feature that prevents the tire bead from slipping inward on the rim and losing the air seal. On ATV's (and UTV's/side-by-sides) this bead retainer is substantially large because these tires are often run at very low air pressures (~5 psi) and experience severe side loading forces from typical trail riding. The large bead retainer is necessary to prevent unintentional dislocation of the tire bead from the bead seat. Further, if an ATV tire does lose pressure from a puncture, the large bead retainer will keep the Tire in place for low speed riding allowing the operator to navigate to the trail head without the tire coming completely off of the rim. The large bead retainers of ATV's do such a good job keeping the tire in place during operating conditions, it also prevents the tire from being easily changed with normal tools even in a shop setting.
There are three categories of tire bead breaker designs: 1) "Shoe and Lever mechanism", 2) "Plier-type mechanism", 3) "Clamp and Ram mechanism". The Shoe and Lever mechanism performs well on many motorcycle tires, passenger vehicle tires and trailers, however with more difficult-to-change tires it often fails because of the nature of the design. The shoe pushes down on the tire sidewall next to the tire bead, and if the bead is stuck, the shoe will simply slide down the sidewall. Further the Shoe and Lever mechanism is quite large, and is not a good portable solution for on-the-trail tire changes. Advantages are typically low cost, often less than $50, and can be found manufactured by many companies. The Plier-Type tool has a spike that pushes in between the tire bead and lip of the rim, and can actually put a separating force on the bead bundle. However the pivot point results in an arc that quickly transitions to pushing on the sidewall. The Plier-type mechanism is more effective than the Shoe and Lever, however it has some disadvantages. It must be adjusted for different diameter wheels, it makes metal on metal contact with the rim, and can easily scratch and mar the surface of aluminum or painted wheels, it takes a bit of coordination and balance to use as you have to stand on the tire and use your body weight to operate the tool, and it is also fairly large, but ultimately is portable and is often used at race tracks for pit-stop tire changes. Ultimately, this type of bead breaker also struggles to work reliably on very stubborn ATV tires, 4x4 trucks, and tractors. The cost of the Plier-type is variable, form $75 to $200, and is manufactured by multiple companies. Lastly, the Clamp-and-Ram mechanism tool  is by far the most effective and compact tool for breaking beads on ATV's and other difficult-to-change tires. This style of tool has a pointed foot that enters the space between the tire bead and lip of the rim, and it uses a padded clamp that is driven with a wrench to get pulled in all the way with very little user effort. The Ram foot then gets actuated by another bolt, with little effort by the user, and it completely breaks the bead loose in one motion. Because the tool is clamped in place, it cannot slide down the sidewall and damage the tire. The ram foot pushes directly on the steel bead bundle of the tire, and therefore works well on old and deteriorated tires.
Tire changers have a semi-automated bead loosening system for removing tires, but due to the high cost and lack of portability these are were not suitable. In addition beads frozen by heat and rust to the rim must often be broken free manually. In these case the bead breaker is ideal. Used like a chisel, a bead breaker leverages a mechanical advantage to drive the bead away from the rim.