What’s In a Rod End

Feb 11, 2010

There’s no two ways about rod ends. They are a serious part that turns into a critical part once they are bolted onto a vehicle or cycle.

There’s nothing cosmetic, dressy or flashy when it comes to the parts that are also called Heim joints, spherical rod bearings or what has become the easiest and most accepted name, rod ends.

Selling these parts has its own set of rules, as just buying them is only one step for your customers. They (and you) need to know more about these parts. So, we asked rod end experts for the critical information concerning these critical components.

It Is What It Is

Let’s start with basics. It may sound silly to ask, but just what exactly is a rod end?

Frank Boling of QS Components explains: “A rod end bearing is a self-aligning spherical bearing used in tension applications to prevent side loading. The bearing itself swivels in order to accommodate the varying misalignment. Applications for rod end bearings include all types of motorsports, linkages, machinery, etc.”

Jeff Stacy of FK Rod Ends tells us, “Very simply, a rod end is a very versatile component that allows motion control. Rod ends were first used in the aircraft industry as a way to connect moving parts that are subject to misalignment. Rod ends are used in various applications to control the movement of chassis and suspension components, throttle and shift linkages and various other pivot points such as steering linkages and anti-roll bar links.”

Bob Douglas of Rod End Supply says, “A rod end is a male- or female-threaded body that has a spherical ball with a hole in it that rotates and/or swivels. A rod end is used as a connector that will swivel or rotate.”

And John McCrory of Aurora Bearing adds, “A rod end allows two components to be connected together with a degree of precision. They are used to replace stock ball joints, tie rods, or suspension bushings in order to provide more precise control, better load-carrying capacity and more freedom in the connection between components.”

What You Need to Know

Applications for rod end bearings include all types of motorsports, linkages, machinery and more. (Photo courtesy Aurora Bearings)When we asked what shops need to know to sell rod ends, Douglas from Rod End Supply responded, “The shops need to know the specifics of the application to know what type of rod end should be used. What type of vehicle is it, and what is it being used for? What type of rod end is available for them to sell and what sizes are offered?”

McCrory of Aurora also stresses education, but from a different direction.

“First, they really need to realize what they don’t know. They then need to speak to their experienced local builders as well as the manufacturer of the parts they sell,” he says. “This is no different than selling shocks or carburetors. You don’t need to know all the particulars, but you have to do the due diligence. Second, you have to get a handle on your core local markets. Is it off-road, drag racing or circle track? The inventory you carry is going to be different, depending on the market. This goes back to the research/due diligence.”

Boling from QS Rod Ends notes, “If a shop is reselling rod ends, the shop needs to make sure that it is buying the right rod end for their customer’s application. They need to keep in mind if it is a vehicle, the weight of the vehicle and what the customer is going to be using it for-”suspension, steering, linkage, etc.”

And Stacy of FK Rod Ends adds, “The absolute most important thing to know about rod ends is quality. They may all look alike, but not all rod ends are the same. Shops need to know where their rod ends come from-”the cheapest option may make more money for the shop at the beginning-”or save the consumer money-”but if it fails or has to be replaced multiple times, what is its true value? Shops need to educate themselves on the technical specifications of the rod ends they are selling so that they can assist their customers in finding the right part for the right application or use.”

That can mean knowing about the materials they are made from, and the fitment of the bearing within the rod end, understanding that different applications require a looser or tighter fit, he explains.

“And whenever in doubt, always step up to the next higher rod end available.”

Installation Suggestions

Our third question was about what consumers need to know about installing rod ends.

When choosing a rod end, keep in mind the weight of the vehicle and what the customer will be using it for. (Photo courtesy QS Components)Stacy starts: “Another aspect of rod end use is the proper usage of jam nuts. Jam nuts are used to hold the rod end in the correct position. It is tightened against the end of the rod end, locking the rod end in its proper location. Using the wrong nut can allow shifting or rotation of the rod end, causing the bearing to bind and ultimately leading to a parts failure.”

Douglas offers these tips: “Put ‘Never Seeze’ on the threads before screwing into the mating component. Make sure they are installed with a jam nut and locked down securely. Make sure that you have 1-1/2 times the threaded shank diameter screwed into the mating part. And make sure the ball has room in the mounting to move freely.”

Boling says, “The best advice on installing rod ends is to make sure that you are getting the full utilization out of the rod end. Making sure that the rod end is not installed on the wrong angle or in a bind. Use a cone spacer or high-misalignment spacer where needed if the application calls for it.”

McCrory adds, “Rod ends are virtually never a straight bolt-in replacement for stock components. If you have a race car or aftermarket component, you have at least a baseline look at what came from the builder/manufacturer. Consult with the component or car builder, as well as the rod end manufacturer. And remember proper mechanics. Check for binding; use proper hardware, torque hardware correctly, etc. Also, remember that the trade-off for the precision and low-deflection of these parts is harshness. A rod end- or spherical bearing-equipped suspension vehicle will not ride as softly or quietly as a stock bushing or ball joint-equipped vehicle.”

What’s Best

Finally, we got even more technical for our last question. We asked how should a shop or user determine which rod end is correct for an application, and how should they measure and calculate the proper size?

McCrory suggests, “Look at existing, successful, reliable examples in the field. Look at a manufacturer’s load capacities. Realize that these are ultimate values, in tension, and apply at least a 4-to-1 factor of safety between the radial static load capacity and the applied loads. Axial loads (loads along the axis of the ball bore) should be kept at 10 percent of the radial static load capacity. For suspension, using a PTFE-lined part is a benefit in terms of fit, friction and maintenance.”

Boling adds, “When determining which rod end is correct for an application, there are a few things to keep in mind. First, consider the material type and load rating or the Ultimate Static Radial Load of the rod end. Material type and load rating are all based on the application. If you are unsure about what type of rod end you need for your application, my best suggestion would be to contact any rod end dealer and they will be able to suggest the correct rod end for the application.

“Second, keep in mind the eye of the rod end or the ID of the ball. Most rod ends have a very common ID hole size, which can be determined by using a pair of calipers or even a measuring tape to determine the ID bore. Third is the shank of the rod end. To determine the tpi or the threads-per-inch, you can use a thread pitch gauge or you can measure the end of the shank to determine the OD and then count the threads per inch on the shank to determine your thread count.”

Douglas keeps it simple: “You must determine what type of vehicle and how the vehicle will be used. The larger the vehicle, the larger the size of rod end.”

And Stacy gives us some food for thought: “Due to legal restrictions and liability issues, we can’t truly answer this question. We can say that it is ultimately up to the consumer to educate themselves on the engineering specifications of their applications to be able to find the correct rod end. If they do not know where to get that education, they can look to a respected chassis builder or speed shop to learn more about the needs of their application. Reputable rod end manufacturers list static radial loads and all the measurements for their rod ends. The information is there, but it is up to the consumer to use that information correctly.”

Rod End Selling Tips

Along with all the knowledge required to understand virtually all aspects of rod ends, selling rod ends is just like selling other parts. There are tricks, tips and secrets to be learned, so we asked our experts for theirs.

Boling of QS Components gives us three safety tips to start with:

“A safety tip for selling rod ends is to make sure your customer gets a quality rod end and make sure your customer is happy with their purchase. A safety tip for buying rod ends is to make sure you are buying a rod end that is going to suit the application it is going on. And a safety tip for installing rod ends is to make sure the rod end’s load capacity is suitable for the application and make sure you are getting the full utilization out of the rod end.”

Stacy of FK Rod Ends tells us: “For selling, always sell them better than what they want. For buying, always buy better than what you think you need. When it comes to installation, use the proper jam nut for your rod end and always keep a regular maintenance routine of cleaning, inspecting and lubricating if necessary. And finally, for anyone, don’t cut corners when it comes to rod ends used in suspension or steering applications. Rod ends are not a place where you can ‘save a little money.’ Rod ends may be a small part, but their importance is vital in so many functions that a rod end failure can quickly lead to a complete failure of the entire system.”

Douglas of Rod End Supply adds, “Always offer the highest quality rod end first. Try and buy the highest quality rod end available. Make sure you have 1-1/2-times the shank diameter for thread engagement.”

And McCrory of Aurora tells us, “Do your homework. Manufacturers, warehouse distributors, local car builders and racers can help bring you up to speed. We offer information on our website, and there are other technical articles or race prep books. An educated seller is always a successful seller. These products are like any other, in that good mechanical fundamentals are important. Knowing about both ends of the business, understanding the mechanics of the product and the needs of the consumer, allows you to service the customer.”