How Does A Bead Blaster on a Tire Changer or A Bead Blaster Gun Work?
A tyre changer's bead blaster system delivers a large volume of highly pressured air into the cavity of a tubeless tyre to help "seat the beads" of the tyre to the wheel assembly. Many tubeless tyres have extremely stiff sidewalls and the beads of these tyres will not seat properly by just pumping air through the valve stem. (Even with the valve core removed)
The "bead blaster" system of the modern tyre changer takes the place of the "spray ether and a match technique" used by tyre people with no regard for their own safety.
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Compressed air is stored in the external tank until that air is needed for the bead blaster. The delivery of the air is controlled by a foot pedal on the machine. When the pedal is partially depressed, the air flows into the tyre through the hose attached to the valve stem. When the pedal is fully depressed, a large volume of compressed air is "blasted" into the cavity of the tyre through holes located on the turntable slide mechanism. (Just behind the clamping jaws). This blast of air occurs while additional air is being introduced through the valve stem inflation hose. The combination of the valve stem air supply and the "bead blasted" air is usually enough to seat the beads of the most stubborn tyres.
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The "blast" of compressed air applies pressure to the top sidewall, temporarily seating the top bead of the tire to the rim. The large volume of compressed air is then directed toward the bottom sidewall and the lower bead of the rim. This process takes less than one second in most car and light truck cars. The continual flow of the air through the valve stem maintains the pressure against both beads; forcing them to seat permanently and allowing the tyre to be inflated to the correct pressure.