When looking for rod end choices for a new project or to update used ones, the quality of your rod end bearing is based on the application. Start by asking yourself the right questions involving rod ends anywhere, from a simple throttle linkage to high-stress rod ends on your front and rear suspension.
Observe the machine work that has gone into each rod end. “The wear life of seemingly similar bearings can vary greatly,” advises John McCrory with Aurora Bearing Company. “This can be due to design and manufacturing control, and often attributed to the make-up and installation of the PTFE liner.”
He continues, “That liner is wearable; for example, there is a big difference between parts store brake pads and proper high-performance brake pads. The same longevity applies to PTFE liners from different bearing manufacturers.”
Judge For Yourself
First, look closely at the rod end. Examine the machine work that has gone into each component in the unit. You can also feel the race; is it smooth or rough? Same again with the ball, smooth or rough? In both cases, the smoother feel and surface finish — the better.
If you’re looking at a non-Teflon lined rod end, you can firmly hold the ball and shake the entire rod end. You can feel the clearances between the ball and the body. Does the rod end rattle, or does the bearing stick in the race? That is a good sign if the fitment seems to fit with precision.
If a Teflon liner is present, look closely for any Teflon liner damage. Are there gaps and pieces missing? It should be a continuous, properly fitting liner around the ball’s circumference. Unlike a non-Teflon lined rod end, the tolerance between the ball and housing should always be very “snug.” When manually moving it around with your fingers it should require some reasonable effort.
Calculating Rod Ends
An informative rod end catalog such as from Aurora Bearing includes specifications for “radial static load capacity,” to which McCrory offers more definition.
“This load capacity is defined as the amount of load, applied either radially, or along the axis of the threaded portion of the rod end,” he says. “A tension load will cause the part to fracture or fail. Axial loads, which are loads through the ball’s axis, are typically recommended to be about 10 percent of the radial load number.
What Strength Rod End Do I Need?
For racing, these bearings are often divided into two categories: the first is suspension joints and secondary are linkages, such as steering. Secondary, or control linkages, include throttle, clutch, brake, and shift mechanisms. Joints in these applications are often low specification industrial/commercial-grade rod ends.
“Race car suspension and steering should use a liner rod end,” instructs McCrory. “These quality rod ends use a carrier fabric for strength, along with a Polytetrafluoroethylene (PTFE) component for lubricity. This type of PTFE-lined rod end offers the optimum in stiffness, strength, and frictional characteristics at a cost-effective price.”