TIRE REMOVAL

Before removing a tire from a vehicle, ensure the emergency brake is locked and the transmission lever is

Figure 3-23.-Rock service tread.

Figure 3-24. - Earthmover tread.

in either park, first, or reverse, depending on the type of transmission. Locate something suitable for blocking the wheels to prevent the vehicle from rolling as you raise it with the jack. Never block the wheels on the axle you are raising with the jack.

For automobiles and light trucks, remove the hubcap, if so equipped, by using the lug wrench or a suitable substitute. Then slightly loosen the bolts or nuts that hold the wheel to the hub. Next, raise the wheel with the jack and observe the vehicle to ensure that it does not roll while being raised. If the vehicle starts to roll, lower the jack and add additional blocking to the wheels. Also, observe the jack and ensure that it does not sink into the ground from the weight of the vehicle. If the jack shows signs of sinking, move the vehicle to a more stable surface or place a plank of solid wood or steel matting under the jack to spread out the ground-bearing pressure. After the wheel has cleared the ground approximately 1 inch, finish removing the lug nuts or bolts and remove the wheel from the vehicle.

CAUTION

Do not leave the vehicle suspended on the jack. If work is to be performed on the vehicle while the tire is removed, place an approved safety stand or suitable blocks under the axle to support the vehicle. If no work is to be performed, install the spare tire as soon as possible to prevent damage to the vehicle or personnel.

On large vehicles with dual-disc wheels, both discs are fastened together by two nuts on each hub bolt, one

Figure 3-25.-Dual-disc wheel mounting.

Figure 3-26.-Truck spoke wheels.

nut for each wheel. Either single or dual wheels can be securely mounted on the same hub with this arrangement. The outer nut must be loosened first to free the outer wheel disc from the hub. Loosening the outer nut, which threads over the inner nut, unfastens the outer wheel disc. In removing dual-disc wheels, you will find left-hand threads on both inner and outer nuts on the left wheels and right-hand threads on those of the right wheels.

Reverse the procedure to mount and tighten the wheels. Dual-disc wheel mounting is shown in figure 3-25.

On trucks having spoke wheels, remove the clamps which secure the rim on the spoke wheel (fig. 3-26), and lift off the rim with the tire and tube. If the spoke has two tires, the second rim and tire can be lifted off after the spacer separating the rims is removed. When installing the wheels, install the outer dual in a position that places the valve stem 180 degrees from the stem on the inner tire (fig. 3-27).