Tire Tech

Tips on Mounting Run-Flat Tires

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You may want to take a copy of this Tire Tech article to the service center when replacing the tires on your vehicle or when having its tire pressure monitoring system (TPMS) serviced. It might provide some tips not covered by the tire changer's normal service procedures.

Tips on servicing tire pressure monitoring systems (TPMS)

While most tire service centers are equipped with "rim-clamp" or "touchless" tire changers, some changers feature rollers that loosen the beads, while others feature side-shovel bead looseners. The rollers loosen the beads as the tire revolves on the changer, while side-shovel bead looseners require the service technician to position, rotate and flip the tire and wheel assembly manually. If you have a choice, a service center equipped with a mounting machine using rollers to loosen the bead is preferred.

The rollers and side-shovel bead looseners must remain positioned on the sidewall near the bead (adjacent to the wheel flange without making contact). If either style bead loosener is placed on the sidewall too far away from the bead, it may damage the tire's rubber sidewall inserts. For example, incorrectly placed side-shovel looseners may distort the sidewall far enough to damage the tire's run-flat insert, identified by one or more "crescent-shaped" cracks visible on the interior of the sidewall when the tire is removed from the wheel.

Bead looseners should begin with the backside bead and only be allowed to press far enough to free the bead from the wheel. Tire lubricant should be applied to the tire and wheel as the bead initially is pushed free of the rim flange. With side-shovel looseners, the tire/wheel assembly must be manually rotated to an adjacent spot to be loosened, and the process is performed repeatedly around the tire until the backside bead is loosened. Then the process is performed repeatedly around the front of the tire until the outside bead is loosened.

The tire should be removed from the wheel following the tire machine's instructions.

Before the tire is reinstalled following the tire machine's instructions, the original TPMS aluminum sensors should be fitted with a new rubber grommet (also called an o-ring or seal), special nickel-plated valve core and aluminum retaining nut. It is important that all components be torqued to appropriate specifications to prevent air leaks. Attempting to reuse the original rubber grommet, valve core and retaining nut may also result in an air leak.

Note: A standard brass valve core used in an aluminum tire pressure sensor valve stem will experience galvanic corrosion, and the brass valve core will eventually seize in the valve's aluminum barrel. Only special nickel-plated valve cores should be used in aluminum tire pressure sensor valve stems.


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