Up until recently, owners of cars and trucks who converted to a multi-link, solid rear-axle configuration have been limited to two decades-old choices in bearing materials. There are the rubber and flexible plastic bushings that have been in use on cars for almost 100 years at one extreme, and spherical rod-ends that date back to WWII on the other. Builders had to choose between these two compromises for street- and strip-driven cars and trucks. That is until recently. Ridetech has eliminated the compromise with its patented R-Joint Rod Ends and Weld-On Spherical Bearings, specifically for these demanding applications.
Limitations of Polyurethane Bushings
As you’re already well aware, rubber bushings and even stiff polyurethane bushings yield under load. Not only does this effect the geometry of the rear suspension, but as they twist through the range of motion, they add resistance to the movement of the axle and increase the effective spring rate. Not good if you’re trying to dial-in your suspension to lower your E.T.
Limitations of Spherical Rod-Ends
Spherical rod-ends, on the other hand, remain consistent in their range of motion but present a challenge for cars and trucks driven on the highway. Spherical rod-ends were developed for aircraft during WWII and haven’t evolved much since. About the only advancement has been the addition, in some versions, of a thin fabric layer coated with PTFE (Teflon).
They are still the connection-of-choice in commercial and military aviation, along with professional race cars, but all of these vehicles have one thing in common — constant and ongoing maintenance. Spherical rod-ends are inspected constantly and replaced at the first sign of wear. That’s an impossible task on a street-driven car or truck that’s subjected to a barrage of grit and grime, grinding away the bearing surface and introducing both wear and additional friction.
The Ridetech Solution
Bret Voelkehl of Ridetech, who already has several suspension patents to his name, gave the issue of bearing and bushings in multilink suspensions a great deal of thought. What he created was a rod-end and spherical bearing ideally suited for this application.
The following video will show the elements of the R-Joint Rod-End and Spherical Bearing. It’s brief and worth watching. We’re going to dig into the details afterwards, so it’s suggested you watch.
Aviation-Grade Stainless Steel
The key to any spherical bearing is the ball, and in the case of the R-Joint it’s manufactured from 304 Stainless Steel. The high amount of chromium and nickel give 304 stainless steel excellent corrosion resistance, exactly the property you want in a component that faces the elements. The housing is manufactured from 17-4 Stainless Steel, whose properties include high levels of strength and hardness, as well as corrosion resistance. It is used extensively in commercial aircraft.
The R-Joint XL housing is investment cast right here in the USA. Investment casting is a process in which a mold is made around a wax pattern that is burned away when the molten material is poured in. The casting of the body then goes through an H900 Solution Anneal heat treatment which increases tensile strength and ductility. The body of the rod-end features rolled threads which are extruded by dies, and are stronger than cut threads (which are made on a lathe) because the grains of rolled threads follow the contours of the rod-end.
Propriety Solution Against Wear
What makes the R-Joint truly different is that the ball isn’t operating inside of a metal or PTFE-coated race, but rather is fitted to a specially-developed cage made of proprietary RTX-10. While Ridetech isn’t sharing any secrets about RTX-10, we presume it to be a material of exceptional strength and stiffness. So with the RTX-10 cage between the ball and the body, you have a material that will stand up to day-to-day abuse on the highway.
The other key element is the unique spring-loaded closure which applies a constant force to the assembly to keep the bearing mechanism tight and rattle free for the life of the product. This is accomplished by a unique combination of a 17-7 Stainless Steel Wave Spring held in position by a 302 Stainless Steel Retainer Ring.
But as they say, the proof is in the pudding, or in this case, Stainless Steel and RTX-10. So what happens when you compare a four-link rear suspension fitted with traditional polyurethane bushings with one fitted with R-Joint rod-ends? Watch this video and be amazed as much as we were:
The video clearly demonstrates why polyurethane isn’t an ideal material for use in suspension systems when there’s a twisting motion involved. It takes force to resist the spring ratio of the poly bushings, which delays the action of the suspension as well as effects the total spring rate. While traditional rod-ends would serve the same function as the R-Joints, they simply don’t stand up to all but extremely minimal street driving and lots of maintenance. So for street and street/strip applications, Ridetech’s new R-Joints offer the best of both worlds.
For a complete range of available sizes, click here for the R-Joint Spec Sheet.