Aurora Bearing Explains Rod End Choices For Racing Applications

When you think of race car rod ends, you can easily visualize some of the most obvious hardware, such as ladder bar or four-link components, but there are typically more rod ends in your car than meets the eye. We did a bumper-to-bumper maintenance overhaul of the Project Rover Camaro and asked John McCrory from Aurora Bearing to chime in on what to inspect and replace when each application’s maintenance intervals come about.

Project Rover is an old-school Super Stocker that has undergone a pandemic-induced overhaul from bumper-to-bumper. We included a close inspection of every rod end on the race car.

The Big Ones: Ladder Bar and Four-Link Rod Ends

Beginning with the rear suspension, we investigated the condition of our Camaro’s ladder bar rod ends. First, we completely removed our ladder bars for an inspection of the bars themselves, including all chassis and differential mounting brackets. We then checked the ladder bars’ spherical rod end bearings.

Our inspection process prompted us to replace several rod ends due to varying factors. Overuse, such as with our main ladder bar rod ends, was obvious. In many other places, there was evidence of "micro-welding," a phenomenon that can take place with rod ends exposed to high motion and load.

Our Camaro reportedly began its life on the dragstrip way back in 1972. Humorously, our front rod ends on the ladder bars appear to have seen use since those days. McCrory explained to us what we were seeing with these aged rod ends.

“In a drag racing suspension, motion isn’t really the driving force when checking rod end wear — it’s actually the force or load itself. In Aurora seminars, we illustrate how much load is put on that joint. But plain and simple, if you have two cars with the same power, one with a four-link and one with a ladder bar, the one with the ladder bar rod ends will see more load on those front rod ends than the four-links.”

The condition of our old rod ends prompted us to also carefully inspect the ladder bars themselves. We exposed and inspected all welds and all internal threads. We also checked all chassis and differential mounting holes to make sure they were not elongated.

Age, rust, and deterioration were obvious, plus the bearing play between the ball and race was mildly loose on one and tight on the other. The most obvious wear characteristic is a “sloppy” ball and race fitment. Depending on the direction of the stress applied, the binding of the ball and race can also occur.

Our Camaro’s left and right ladder bar rod ends exhibited these two different symptoms. McCrory discussed with us this abnormality, and the conclusion was the two ladder bars were exposed to two very different forces due to starting line torque and body twist. If you have ever observed a drag car spitting the differential out from under the car, we can’t help but imagine we were dangerously close to that scenario.

A rod end consists of three basic components, including the outer housing, the bearing race, and the ball. This closeup of our new ladder bar rod end shows the additional PTFE liner on the bearing race surface.

Our tired rod ends were replaced with fresh pieces from Aurora. McCrory recommended the AM-series rod end , which is constructed from a high-strength alloy and features a self-lubricating Polytetrafluoroethylene (PTFE) lined inner race for the ball to ride on. This rod end has a PTFE impregnated woven fabric liner between the ball and race.

This PTFE liner design by no means sacrifices strength to the overall rod end. This specific 3/4-inch rod end has an ultimate radial static load capacity of 28,081-pounds.

“There are advantages to a PTFE/Teflon-liner,” McCrory explains. “They are self-lubricating, and second, these rod ends are also designed with zero-clearance between the ball and race. A standard rod end with no liner must have a small amount of clearance for the ball to move within the race.”

McCrory continues, “A rod end with small clearances will grow into larger clearances over time as the bearing works within the housing. A PTFE liner offers improved frictional characteristics and zero tolerance. This eliminates the initial clearance that can grow, resulting in a longer-lasting and lubricated rod end.”

Rear Suspension Track Locator

Another point needing inspection on our rearend is the diagonal link-style track locator that serves to keep the ladder bar suspension centered. Several designs serve this purpose, all of which use rod ends to keep the rearend centered while also allowing the rear suspension to function.

McCrory suggested we upgrade our worn diagonal link rod ends by using a pair of Aurora's high-strength ends that also utilize the PTFE liner. Our original rod ends use a shank incorporated into each side of the rod end. For replacements, we used heavier-duty misalignment bushings and standard width rod ends. We also updated the solid rod ends at the rearend with new hardware from Quarter-Max.

Our diagonal-link rod ends were not damaged or overly worn, but we did perform a close inspection to make sure the rod end bodies were not damaged from too much deflection. The typical rod end can only see 16- to 20-degrees of misalignment angle before body damage could possibly occur.

Steering Rod Ends

Unlike our ladder bars, the two rod ends connecting our Pinto-style rack-and-pinion steering and the steering arms have very different duties. These rod ends expose the ball and race to rapid motion as the suspension travels, combined with steering duties.

We made a careful inspection of the bearing surfaces of our rack-and-pinion rod ends. Shown in this example image, the discoloration and rough surface of the spherical ball indicate micro-welding. This form of wear results from surface heat between the ball and race caused by their rapid motion under load.

“With these conditions, you can see wear indicators as adhesive wear,” McCrory points out. “A metal-on-metal rod end exposed to a lot of force and motion can actually surface-weld the bearing surfaces together on a microscopic level.”

McCrory adds, “If this happens, the surface appears discolored, gritty, or rough on the chrome-plated ball. Progressively, the surface turns brown or black as it continues to heat up. This damage forms as the surfaces are microscopically welded and subsequently pulled apart. The more surface damage that exists, the more severe micro-welding and failure can occur.”

With the new Aurora throttle linkage rod ends in place, you notice the heavy-duty body compared to our original hardware. We definitely will have more peace of mind when whacking the throttle.

Our steering rod ends are now replaced with 1/2-inch PTFE-lined units constructed from alloy steel and heat-treated components. With all of these lined rod ends, the ball is not easily moved around with your fingers. The zero-clearance design prevents wear, and in this case, our micro-welding problem.

Our steering shaft is supported by a rod end that prevents binding between the multiple steering knuckles. We immediately noticed how smooth our steering became once we replaced its predecessor.

Example: A Simple Rod End That Cost Us A Big Race

Imagine you’re in the late rounds of a big-dollar race and your transmission shifter linkage fails following your burnout. It’s not hard to imagine a relatively inexpensive link between your trans and shifter cable costing you a race.

The typical hardware within many shifters is a small threaded “puck” and cotter pin retainer that controls the transmission’s gear select arm. For our application, McCrory suggested the highly durable KW series rod end. Though comparably smaller than our suspension and steering ends, these SAE #10 rod ends feature a low-carbon steel body and an alloy steel ball and race.

This rod end upgrade suggested by McCrory threads onto the shifter’s cable and operates smoothly. This is far more durable than the tiny cotter pin retainer that once let us down.

Named for “teaching an old dog new tricks,” Project Rover’s motto could not be more appropriate when applied to the various rod ends in use throughout the entire car. Some handle extreme loads, such as our ladder bars. Others safely center the suspension, steer, or simply operate the throttle.

Even the small rod ends at the shifter play an equally vital role in reliably transferring motion. If an incorrectly specified or aged rod end would fail, it could spell anything from losing a race to causing severe suspension damage.

Next time you’re having “maintenance day,” add a close inspection of all your rod ends, scrutinizing if they are excessively sloppy, tight, or visually worn — as it’s something not to take for granted.

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About the author

Todd Silvey

Todd has been a hardcore drag racing journalist since 1987. He is constantly on both sides of the guardwall from racing photography and editorship to drag racing cars of every shape and class.
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