How to Choose Rod Ends for Your Vintage Racer | Project Elva Sports Racer

There might be places to save a buck or two when restoring a car, but not when it involves suspension parts. Think about the children.

As part of the restoration of our Elva sports racer, we needed to replace all of the rod ends used to tie everything together. So we turned to Aurora Bearing Company for help, as this company specializes in rod ends and spherical bearings.

We’ve worked with Aurora on several projects, and the company has always offered useful information and carried just what we needed.

First, we got a history lesson–and don’t worry, soon we’ll talk more about specifics and what we ordered for replacements.

Your rod ends are very old,” noted John McCrory, race car product manager at Aurora Bearing Company. “The ½-inch parts are Sphercos, and they have to be close to 50 years old!”

McCrory said that our rod ends came from Spherco’s ARE series–three-piece units made with 4130 chrome-moly bodies.

Backing up: What’s a Spherco?

It’s a rod end once made by Sealmaster in Aurora, Illinois, home of Aurora Bearing. “They were the only commercially available rod ends with 4130 heat-treated body and race,” McCrory explains. “They weren’t as sophisticated as the Transport Dynamics or Southwest rod ends that Carroll Smith recommended, but mere mortals could buy them.

In 1969, Stephens Adamson, an Aurora producer of conveyors and related bearings, sold their Sealmaster division to BorgWarner, who merged the acquisition into their Morse division.”

As McCrory explains, the relationship quickly came off the rails.

First, after meeting with the new ownership in Ithaca, New York, a group of Sealmaster employees from different areas of the company decided they didn’t like the direction the company was heading. The seeds were sown for the formation of Aurora Bearing, which occurred in 1972.

Second, BorgWarner decided that rather than manufacture rod ends and spherical bearings, they would contract to purchase products from Heim. Heim did not manufacture a part equivalent to the ARE series, so by the mid-1970s that part disappeared from the market.”

McCrory explains that every now and then, someone doing a restoration would ask him about replacements for old ARE-series Spherco rod ends–which, he adds, have a unique head profile.

The rod ends that are now marketed are different,” he continues. “It never appeared to be a commercially viable option to make parts to match the Spherco style.”

But there was a eureka moment a few years ago, when Aurora displayed an old Gerhard Indy car in its PRI Trade Show booth.

It had Spherco parts,” McCrory continues. “At that point, we evaluated the options to produce similar-appearing parts and found a way to make the Spherco-style part in ½-, 5/8- and ¾-inch sizes. These would cover suspension applications for Indy roadsters, many U.S.- produced rear-engine Indy cars and others.”

History is great, but we still needed to order fresh rod ends.

Aurora offers different grades of these joints, from economy to aerospace, each appropriate for different applications. After consulting with McCrory, we decided to use the AM-T-46 series of parts, which feature heat-treaded alloy steel bodies, the “Spherco style” head profile, and PTFE liners. (PTFE, short for polytetrafluoroethylene, is a synthetic polymer; DuPont offers this type of compound under its Teflon brand.)

The key benefits of PTFE-lined rod ends are zero clearance, self-lubricating and low-friction fit,” McCrory explains.

Another factor to consider when replacing rod ends: male or female threads? We needed both: Our trailing arms used male threads, while our anti-roll bar links had female threads.

And we needed to take measurements. McCrory walked us through the process. For a spherical bearing, he explains, there are four key dimensions:

  • B: ball bore (hole size)
  • D: outside diameter
  • H: width across raceway
  • W: width across the ball bore

For a rod end, he continues, ball bore, threads and orientation dictate more than 90% of the size interchange. Helpful and relevant is the measurement from the base to the center of the ball (A) and the head diameter (D).

While current rod end manufacturers adhere to an industry dimensional convention, this has not always been the case,” McCrory advises. “You’re more likely to see variations with vintage cars as opposed to something from recent time–the last 20 to 30 years.”

Another note of caution: “A thread pitch gauge is useful, especially to help pick up inch versus metric. Inch (or imperial) rod ends are UNF-thread; metric threads can be coarse or fine. What at first glance appears to be a coarse-thread 5/16 rod end is likely a metric 8mm with M8x1.25 threads.”

And one more heads-up: “Another wildcard is old British cars–pre-mid-’60s–that could have BSF threads.”

When replacing rod ends, he notes, any markings on the product can be helpful.

The rod ends on our anti-roll bar end links had BSF threads. Since Aurora doesn’t sell any products with BSF threads–and since we couldn’t find them anywhere else–we had new end links made with SAE fine threads. We also sourced CW-6 rod ends with the following specifications:

  • Bore diameter: 3/8 inch
  • Threads: 3/8 inch SAE fine
  • Overall length: 1.75 inch
  • Barrel width: ½ inch

The rear trailing arms sported SAE fine threads, so we simply used Aurora’s modern take on those old ARE pieces. The part number is AM-8T-46, and here are the dimensions:

  • Bore diameter: ½ inch
  • Threads: ½ inch SAE fine
  • Overall length: 3 inches
  • Barrel width: 7/16 inch

We ran a tap through the trailing arms to clean up the threads, used some ½-inch SAE fine nuts to lock the rod ends in place, and we were good to go.

Running a tap to clean up gnarly, 50-year-old threads is good,” McCrory notes. “It’s bad, very bad, to try to change BSF threads or metric threads to inch dimensions.”

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View comments on the CMS forums
8/15/21 12:53 p.m.

Would be great to see the latest progress on the Elva.

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