Issue link: http://read.dmtmag.com/i/34501
Warning: Correct components must be used. It is important to note that some hub piloted and stud piloted wheels may have the same bolt circle pattern. Therefore, they could mistakenly be interchanged. Each mounting system requires its correct mating parts. It is important that the proper components are used for each type of mounting and that the wheels are fitted to the proper hubs. If hub piloted wheel components (hubs, wheels, fasteners) are mixed with stud piloted wheel components, loss of torque, broken studs, cracked wheels, and possible wheel loss can occur since these parts are not designed to work together. Mixing hub piloted and stud piloted wheels will not allow the inner cap nut to fit into the inner wheel and will result in the inner cap nut interfering with the outer wheel. (Figure 1) Stud Piloted Wheel Drum Hub Hub Piloted Wheel Outer Cap Nut SPECIAL CONSIDERATIONS FOR ALUMINUM WHEELS It is also important to note that the disc thickness of aluminum wheels is usually much thicker than steel wheels, and stud length must be checked when changing from steel wheels to aluminum wheels. Aluminum wheel disc thickness ranges from 3⁄4" to 1-1⁄ 8". This is approximately double the thickness of steel disc wheels. Because of this increase in disc thickness, special consideration must be given to aluminum wheel attaching hardware. Wheel stud lengths are specifically designed to suit varying disc wheel mounting systems, brake drum mounting face thickness, and disc wheel material types. Failure to use the correct length studs may lead to insufficient clamp load of the disc wheels. The minimum length for dual aluminum wheels is 1.06 inches or 27 mm as measured from the brake drum face when mounted on the hub. The pilot must engage 1⁄ 2 of the thickness of the aluminum wheel. Refer to TMC RP 217B, Attaching Hardware for Disc Wheels. Hub Bore and 15 degree bead seat measuring tools are available from the wheel manufacturers. (Figure 3) Aluminum Wheel Stud Inner Cap Nut Figure 1: Improper Mounting Stud Ball seat, stud piloted wheels should not be used with flange nuts because they have larger bolt holes and do not have sufficient area near the bolt hole to support the flange nut. Slippage may occur. Also the center hole is too large to center the wheel. (Figure 2) Stud Piloted Wheel Drum Hub Two-Piece Flange Nut Inner Cap Nut Figure 3: Correct An out-of-service condition exists if the area between the bolt hole ball seats is worn away to less than 1⁄16th inch (the approximate thickness of a dime). If this is the case, the wheel should be scrapped. (Figure 4) Steel Wheel Hub Stud Stud Figure 2: Improper Mounting Figure 4: Incorrect Inner Cap Nut Hub Section Nine: Appendix 127