GENERAL MOUNTING INSTRUCTIONS

REMOVAL FROM LANDING GEAR

In order to properly track reasons for tire removal and to take appropriate action, it is very important to have accurate information regarding tire removal. This information helps the retreader or repair station to make decisions concerning inspections and the future use of the tire.

Recommended information includes:

Name of Operator
Date of dismounting
Aircraft model
Tail number
Tire part number
Tire serial number
Reason for removal
Number of tire landings

It is further recommended that removal information accompany the tire to the repair station or retreader. The simplest approach is to use a tag or label attached to the tire with a self-sticking adhesive (applied to lower sidewall) or by use of heavy or nylon string.

Caution: Do not use staples or other metal devices for affixing tags or labels to tires or inner tubes. Keep adhesive labels above the bead area of the tire.

A sample label is shown below.

TIRE DISMOUNTING

Proper dismounting procedures simplify the job of servicing aircraft tires, while increasing safety and reducing the chances of damaging tires or wheels. The task of dismounting tires should not be undertaken without proper equipment, instructions and trained personnel.

Careful attention must be given to disassembling and handling wheel components to avoid damage to critical surfaces. To assist in this process, wheel manufacturers publish specific instructions in their maintenance and overhaul manuals. Follow their recommendations and procedures to assure trouble‑free dismounting.

Tire/Wheel Dismounting Sequence

The same methods are essentially used for dismounting tubeless bias, tube-type bias and radial aircraft tires. However, radial tires have a smaller bead flat area and have a more flexible sidewall, which requires that more attention be placed on the tooling set up. Failure to use proper tooling designed for the particular tire size could result in dismounting difficulties. Follow the tooling guidelines given in the next section.

Once tooling has been set-up, dismounting should occur in a similar manner for both bias and radial tires, tubeless and tube-type.

  1. Before beginning any tire dismount, be sure to follow the instructions and precautions published in the wheel supplier's maintenance manual.
  2. Mark damaged or bulge areas before deflating, using a contrasting color chalk.
  3. Completely deflate the tire or tube before dismounting.
    1. Use caution when unscrewing valve cores. The pressure within the tire or tube can cause a valve core to be ejected at high speed.
    2. If damage has occurred, a tire/wheel assembly should be deflated in a protective cage.
  4. Use a bead breaker to loosen tire beads from both wheel-half flanges.
    1. Always use proper bead breaking equipment designed for separating tires from wheel bead seats. Do not use pry bars, tire irons, or any other sharp tools to loosen tire beads. Damage to the tire and wheel may occur.
    2. Do not loosen wheel tie bolts prior to breaking the beads loose. Damage to the mating surfaces of the wheel halves can occur.
    3. Ensure that the adaptor rings of the ring type bead breaker have passed over the wheel flanges and do not interfere with any wheel components.
    4. Ensure the faces of the adaptor rings or press pads, in contact with the tire, are free of nicks, burrs or sharp edges which could damage the tire surfaces.
  5. Apply bead breaker ram pressure or arm pressure slowly or in a series of sequences or jogs to allow time for the tire's beads to slide on the wheel.
    1. Because of the flexible sidewalls of a radial, use of incorrect tooling or applying pressure too rapidly can cause sidewall distortion. Heavy distortion of the sidewall is not only harmful to the internal tire components, but it may also begin to "roll" the beads, making dismounting more difficult.

WHAT TO DO IF THE TIRE BECOMES FIXED TO THE WHEEL

If a tire bead rolls such that it will no longer slide on the wheel:

  • Release ram pressure.
  • Apply a soap solution to the tire/wheel interface. Allow several minutes for the solution to penetrate between the tire and wheel.

Note: Do not use hydrocarbon-based lubricants. These can be harmful to the rubber components of the tire.

  • Reapply a reduced hydraulic pressure to the tire.
  • Repeat several times if necessary.

If the tire still remains fast:

  • Remove the tire/wheel assembly from the machine.
  • Reinflate the tire in a cage until the bead moves back to its correct position.
  • Deflate the tire.
  • Recommence the dismounting procedure following the same procedure.

Note: Cases of bead roll over should be reported to the retreader who will examine the tire for damage. A tire found to have been damaged should be scrapped.

  1. Remove tie bolts and slide out both parts of the wheel from the tire.
  2. For tube-type tires, remove the tube.
  3. Tire is now dismounted.

TIRE DISMOUNTING EQUIPMENT

The primary component for dismounting an aircraft tire from its wheel is the bead breaking equipment used to loosen the tire from the wheel bead seats.

Two types of bead breaking equipment can be identified here:  

  1. The "ring" type bead breaker.

Bead breaking is performed by pushing a movable adapter ring against the lower sidewall of one side of the tire. The opposite side consists of a stationary adapter ring that also contacts the lower sidewall of the tire.

It is important that the "adaptor" rings be designed for the particular tire/wheel assembly to be dismounted.

The optimum condition is an adapter ring internal diameter as close to the wheel flange diameter as possible. Pushing too high on the tire sidewall will only distort the sidewall and bead area, making dismounting more difficult.

For practical purposes, a radial clearance between the tip of the wheel flange and the internal diameter of the adaptor ring is necessary to avoid interference between the wheel and adaptor ring as it approaches and travels over the wheel flange.

Michelin recommends a radial clearance of 0.4 inches (10mm).

The movement (travel) of the adaptor ring should be at least four (4) inches (100mm) to ensure complete separation of the tire from the wheel.

It is desirable that the rings be designed such that the tire can be observed while pressure is being applied, to ensure satisfactory ring contact and progress.

  1. Localized "pincher" type bead breaker

This equipment consists of two press arms which can be operated in a "pincher" movement. At the end of each arm is a press pad in the form of a sector. An adjustable cylinder is used to position the tire so that the sectors can be matched to the size of the tire.

The tire/wheel assembly is positioned such that the press pads contact the tire's lower sidewall just above the wheel flange.

Pressure is applied to break the beads. After the first sector of the tire is free, the tire/wheel assembly is rotated and the operation is repeated (usually three times) until all sectors of the tire are loose.

The press pads used to push the tire are "universal" and are designed to push on the tire close to the wheel flange. No specific tooling is required for the different tire sizes to be handled.

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