TIRE REPAIR

Facilities for repairing tires vary from one location to another. Some deployment locations have power-operated tire repair equipment to support tire repair. This

Figure 3-27.—180-degree valve stem location.

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Figure 3-28.—Pneumatic tire demounter.

Figure 3-29.—Pneumatic tire spreader.

Figure 3-30.-Inflation safety cage.

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equipment is similar to those shown in figures 3-28 and 3-29.

The first step in tire changing is to remove the valve core and deflate the tire completely. When using any tire repair equipment, install the tire and rim by closely following the manufacturer’s instructions. The pneumatic tire demounter holds the wheel and tire still while it breaks the tire bead loose from the wheel rim.

An adapter is used to remove the tire from or replace it on the rim. Tire demounters are manual, hydraulic, or air-operated. The one shown in figure 3-28 is an air-operated demounter for automotive and light truck tires.

NOTE: All of the related instructions for the use of tire shop equipment must be posted in the tire shop.

The spreader (fig. 3-29) separates the tire beads enough to allow close inspection and maintenance on the inside of the tire. When mounting a tire, inflate the tube until it is almost round. Put the inside bead of the tire on the rim and insert the tube into the tire with the valve at the balance mark on the tire. Place the valve stem through the hole and make sure that it is perpendicular to the hole. This step prevents chafing and damage to the valve stem during vehicle operation.

When installing the second bead on the rim, start on the opposite side from the valve stem.

Place the tire and wheel in an APPROVED SAFETY CAGE (fig. 3-30). After mounting it on the rim, inflate the tire slowly. Make sure the tire beads fit snugly against the rim flanges. You may have to over-inflate the tire at first to make the bead seat on the rim.

Once seated, allow the tire to deflate and install a new valve core. Then inflate the tire to the recommended pressure.

Unless your tire shop is well equipped, machinery for repairing truck tires, such as split rims and rims with removable side rings, may not be available or may not work on the various types of wheels and rims you may

Figure 3-31.—Locking ring rim.

have to repair. When repairing tires with locking rings (fig. 3-31), first remove the valve core and deflate the tire. Force the tire bead away from the removable side ring with a slide hammer device intended for this purpose. Next, remove the side ring, as shown in figure 3-32, views A and B. Turn the wheel and tire over and

Figure 3-32.-Demounting and mounting a military truck tire.

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loosen the other bead. Once the beads are broken, the tire can be removed from the rim by standing the tire on the thread and prying the wheel out of the tire. Ensure the valve stem is not bent or damaged as the wheel is r e m o v e d .

To replace the tire, position the wheel, as shown in figure 3-32, view C. Lower the tire over the rim, and at the same time, make sure the valve stem is passed through the valve hole and points upward.

NOTE: The valve stem should always point toward the removable side ring. If there is no side ring, point it toward the disc portion of the wheel.

The next step is to center the side ring and force one end into position with your foot. Then the ring can be installed as shown, or the repair person can merely walk around the top of the ring and force it to slide into the locking groove. Inflating a tire mounted on a locking ring rim is dangerous. An improperly seated lock ring may blow off, causing serious injury to you or any other person in its path. A sprung ring, or one which is bent or twisted, may be difficult to install and, if used, is a safety hazard and should be replaced. Before applying air pressure to this tire, be sure that the locking ring is seated against the rim of the wheel through its entire circumference. If the lock ring does not seat properly, inflate it to 5 to 10 pounds, then tap the locking ring carefully with a mallet. NEVER STAND IN FRONT OF OR OVER THE LOCKING RING. ADDITIONALLY, REMEMBER TO USE THE SAFETY CAGE FOR INFLATION. When you have to inflate a tire that is already mounted, use a snap-on chuck which is an air hose that snaps onto the valve stem. This allows you to stand to one side of the tire. Make it a professional practice to never stand in front of a tire being inflated.

Tubeless Tire Repair

Some tires are tubeless. Instead of being sealed in an inner tube, the air in these tires is sealed in a space between the outer casing and the rim. Both this space and the point of contact of the tire against the rim must be airtight. The rim, on which the valve for inflating the tire is mounted, becomes a part of the air-retaining chamber. Do not tear or otherwise injure the sealing ribs.

Before replacing a tubeless tire, examine the rim carefully for dents, roughness, and rust; any defects may impair or break the air seal. Straighten out any dent with a hammer, and use steel wool or a wire brush to clean

the bead seat area of any rust or grit. After cleaning, paint any bare metal spots where the tire bead seats to make it easier to remove the tire later. If the rim is badly damaged, replace it with a new one.

The procedure for repairing a tubeless tire is accomplished by the following steps:

1. Inspect the inside of the tire and remove nails or other damaging items. Then scrape the damaged area with a sharp-edged tool and buff (fig. 3-33, step 1). Be careful not to damage the liner or expose any cords.

NOTE: Serious injury can result using your bare hand to free for obstructions, use a rag to feel inside the tire.

2. Lubricate the hole by pushing bonding compound into the hole from both sides of the tire (fig.

3-33, step 2). Also, pour bonding compound on the insertion tool and push it through the hole with a twisting motion until it can be inserted and withdrawn easily.

3. Using a plug slightly larger than the hole, place it in the eye of the hole of the insertion tool. Wet the plug with bonding compound. Always pour it directly from the can so the contents in the can does not become contaminated, as shown in figure 3-33, step 3.

4. While stretching and holding the plug with your hand, insert the plug into the hole from the inside of the tire. Stretch and hold the plug until it is forced into the hole and one end extends through it, as shown in figure 3-33, step 4.

5. After the plug extends through the tire, remove the insertion tool and cut off the plug approximately

1/16 inch above the surface (fig. 3-33, step 5).

6. When using a cold patch, carefully remove the backing from the patch and center the base of the patch on the damaged area. Stitch the patch down firmly with the stitching tool working from the center out (fig. 3-33, step 6).

7. When using a vulcanizing hot patch, cover the area with a light coat of glue and allow it to dry. This glue normally comes with the hot patch kit. Remove the backing from the patch and center it on the damaged area. Clamp it finger tight, apply heat, allow to cure, and then cool. (fig. 3-33, step 7).

NOTE: Each patch or plug kit should contain specific instructions.

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Figure 3-33.—Repair of tire punctures

Punctured tires can be repaired without being removed from the rim. In this case, the insertion of the plug is performed from the outside in, and steps 6 and 7 of figure 3-33 are not required.

NOTE: For radial-ply tires, repairs can only be made in the central tread area between the major grooves.

The procedures for removing and remounting a tubeless tire are similar to that for tube tires. If the seal is broken or defective, use a tube inside the tire;

otherwise, the tire will lose air, and you will have to inflate it frequently. Some tubeless passenger car tires must be removed from the backside of the rim to prevent stretching the bead wires too far and causing them to break. If in doubt about any detail of the procedure for changing tubeless tires, follow the tire manufacturer’s instruction or consult the maintenance supervisor.

Earthmover Tire Repair

When major damage or a blowout occurs or normal wear limits have been reached, the tire must be removed.

Size alone makes the removal and replacement of earthmover tires difficult. Additionally, the nature of the terrain over which they operate often cause conditions to be far from ideal. Certain tools are necessary to change these large tires. The hydraulic bead breaker is specifically designed to break the giant beads for easier removal of the tire. BEFORE ATTEMPTING TO REMOVE THE TIRE, MAKE SURE THE WHEEL HAS BEEN JACKED UP AND THE EQUIPMENT PROPERLY BLOCKED FOR MAXIMUM SAFETY.

After the equipment has been safely cribbed, deflate the tire completely by removing the valve core.

The clamping device is used to aid in unseating (breaking) the tire beads. Attached to the rim flange, it

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holds the hydraulic ram and shoe assembly. When device in place with one hand and tighten the large securing the clamping device (fig. 3-34) to the rim, clamping screw lightly. Swing the reaction screw, as release the primary clamping device to permit full shown, until it is approximately perpendicular to the opening of the jaws. Hold the clamping device in a side of the rim flange. Turn the reaction screw in to bring vertical position, as shown. Then hold the clamping the clamping device perpendicular to the rim. Tighten

Figure 3-34.—Clamping device.

Figure 3-35.—Hydraulic cylinder and shoe.

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the primary clamping screw firmly by hand. When the clamping device is secured in place, turn the handle on the bottom of the reaction screw. This handle swivels up and down to permit maximum movement of the clamping device side arms to ease hooking the ram cylinder into place.

The hydraulic cylinder and shoe assembly (fig.

3-35) are actuated by a pump. The pump applies hydraulic pressure that forces the ram with the attached shoe down between the rim flange and tire bead. This action separates the tire bead and rim.

When securing the ram to the clamping device, place the ram and shoe assembly between the arms of the clamping device where the bracket of the cylinder is secured into the notches of the clamping device side arms, as shown in figure 3-35.

Applying pressure to the hydraulic cylinder forces the shoe down over the clamping device, as shown in figure 3-35. The jaws of the clamping device acts as a guide for the shoe. The convex side of the shoe bears against the sidewall of the tire, forcing it inward between

the tire bead and rim flange, thus breaking loose the bead from the rim.

Figure 3-36 shows how the wedges are placed on each side of the shoe assembly to hold the bead of the tire away from the rim flange so that the shoe assembly can be easily removed. After the shoe has been forced between the tire bead and rim flange and freed from that portion of the tire bead, the wedges are inserted to keep the tire bead separated from the rim. Pressure is then removed from the hydraulic cylinder slowly. The hydraulic cylinder and clamping device are then removed from the rim and the clamping device is placed approximately 90 degrees from the wedge. This process is continued until the tire bead is completely free from the rim flange.

Cold Patches

Cold patches are used to repair punctures and small breaks or holes in tubes. The procedure for applying a cold patch is accomplished by the following steps:

Figure 3-36.—Operation of hydraulic cylinder and shoe.

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1. Buff or roughen the tube surface to be patched for at least 1 inch around the hole. Then clean it with solvent. When a buffer is not available, use the perforated cover of the kit as a scraper.

2. Apply a thin coat of rubber patching cement evenly over the roughened surface and allow it to dry.

3. From the kit, choose a patch of the proper size that is about 3/4 inch larger than the hole in the tube from the kit. Remove the protective covering from the sticky side of the patch; place the patch over the hole, and rub it down firmly.

4. Inflate the tube with enough air to check for leaks. If you cannot hear or feel air escaping from the patch, you can make another check by inserting the patched area in water. If no escaping air bubbles are noticed, the tube may be dried and replaced in the tire or stored.

tube, the burning material is ignited, allowed to burn, and then removed after cooling for at least 5 minutes.

After this, examine the completed patch to see if the edges of the patching material are attached securely to the tube. Then install the valve core and test the tube.

Hot patches of assorted sizes are supplied in kits similar to the cold patch kits. You will also find pressure clamps and roughening tools in the hot patch kits.