NUTS ABOUT BOLTS (Part 2)
Bolts, nuts, and washers: They hold your ride together. But how well are they doing their job? Hopefully, you’ve read our primer on engine and driveline fasteners chiefly subjected to tension loads: forces mainly exerted on a fastener’s longitudinal axis (Dec. 2019). With the help of the good guys at ARP, we explained why specialty bolts matter and how metallurgy, heat treating, and proper tightening procedures are critical for tension fastener survival. Most of us understand the need for specialty hardware as it applies to a drivetrain’s power-making and power-sustaining parts, but the same concern and care isn’t always applied to fastener selection and installation when it comes to other critical parts subject primarily to sideways or bending forces. Engineers term these forces, exerted perpendicular to a bolt’s axis, “shear” loads. Examples include most fasteners used to retain suspension components, but also pulleys, balancers, flywheels, timing sprockets, road wheels, antiswaybar ends, and the like. This time, we’ll get into the proper selection of fasteners for shear applications, as well as touch on some problem-solvers.
GO DOUBLE, AVOID TROUBLE
If a bolt loaded in shear is supported on one side of the load only, it’s said to be installed in “single shear.” If the bolt is supported on both sides of the load, it’s in “double shear,” and the installation is significantly stronger than an equivalent single shear mount because it spreads the loads over a greater area while better resisting bending loads. All deformation and induced loads are now in the same plane, minimizing twisting. Rod-ends on four-link suspensions, Panhard bars, Watt’s linkage, steering
