Webb Catalog

Cast-in vs. Drilled Bolt Holes

Webb Wheel Products has recently added cast-in drum holes to a limited number of

brake drum part numbers. Currently, the drilled bolt hole size for standard hub

piloted applications is 1.0" while the as-cast bolt hole is approximately 1.17" in

diameter.

The slightly larger bolt hole feature size does not affect the fit, form, or function of

the brake drum and only serves as a clearance hole for the wheel stud. The brake

drum is centered onto the hub using the 8.78" machined pilot and the bolt holes

serve no piloting function at all. When wheel nuts are properly tightened, each

wheel stud delivers approximately 20,000-40,000 pounds of tension into the bolted

joint. The slightly larger hole size has no effect on the bolted joint's clamp load and

will not allow the drum to move in the radial direction under braking or acceleration

loading.

If you have any questions regarding cast-in wheel bolt holes, please feel free to call

Webb's Technical Support department.

Standard Drilled Holes As-Cast Holes

BRAKE DRUM AND ROTOR SERVICE INFORMATION

TROUBLE-SHOOTING: CAST-IN VS. DRILLED BOLT HOLES

Webb Wheel Products has recently added cast-in drum holes to a limited number of brake drum

part numbers. Currently, the drilled bolt hole size for standard hub piloted applications is 1.0” while

the as-cast bolt hole is approximately 1.17” in diameter.

The slightly larger bolt hole feature siz does not affect the fit, form, or function of the brake drum

and only s rves as a clearanc hole for the wheel stud. The brake drum is center d onto the hub

using the 8.78” machi ed pilot and the bolt holes serve no piloting function at all. When wheel nuts

are properly tightened, each wheel stud delivers approximately 20,000-40,000 pounds of tension

into th bolted joint. The slightly larg r hole size has no effect on th bolted joint’s clamp load and

will not allow the drum to move in th radial dir ction u der raking r acceleration loading.

If you have any questions regarding cast-in wheel bolt holes, please feel free to call Webb’s

Technical Support department.