Stim.Tech Articles

Product Overview: E30 Spherical Bearing RTAB Inserts

February 23, 2018 Suspension 0 Comments

It is our hope that the only thing lacking in this post is the below-par cell phone pictures used. Perhaps the generation old smart phone, which has spent the past two years in a pocket lined in metal dust; “ain’t what it used to be”.

Now that we have completed a production run of our E30 Rear Trailing Arm Spherical Bearing Insert Sets (something in that title has to change) we felt it was time to provide an overview of the various components and their function which make up this set.

A common topic in the realm of E30’s is the rear subframe/suspension assembly, more-so the problems and various solutions of the aforementioned. There exists, a plethora of rear trailing arm bushing designs available, all of which have their own benefits. However, we always discussed the possibility of fitting spherical bearings to the trailing arms. In our previous post on this topic, we discussed the reasoning to switch from a conventional sleeve bushing to a proper spherical bearing. Simply said, utilizing these bearings will remove binding which can occur in traditional bushings. As well, they allow movement only in the axis desired, removing compliance in all other axes.

The beautiful specimen pictured above is the subframe out of our LS-1 swapped test car. Complete with the standard Eccentric Adjusters and Condor Motorsports SF Bushings , we have fitted here, our Spherical Bearing Inserts.

The Spherical Inserts install and function as a standard bushing would. Below, an arm with our Spherical Insert installed is shown. In congruence with a conventional bushing, these press into the arm bores from the outside and the sleeve flange sits against the arm on the “thick side”.

The Bearing Sleeves are machined from billet chromoly steel, meaning that the inserts are not forgiving when being pressed into the trailing arm bores. For this reason, we provide a sacrificial guide tool for the install process.

This guide tool locates inside of the Bearing Sleeve and is machined to a locational clearance fit on the trailing arm bore. With the guide tool leading into the trailing arm, it is ensured that the installer has the Bearing Sleeve axially aligned with the bore. Of course, brief instructions and warnings are listed on the product page for the install of these. The last thing we want is a fellow e30 friend trying to “bench-vise” these bad-boys in and causing a cataclysmic disaster.

The machined components used in these inserts are turned from billet chromoly. Traditional spherical sleeves are made from aluminum, due to the minimal build height of these assemblies, aluminum was not an option. Below, our Bearing Sleeves can be seen in raw turned form prior to the micro-finish process.

The Bearing Sleeves and the Bearing Spacers are finished with a gloss black zinc plating process. This micro-finish promotes corrosion resistance and longevity in the material. Below the Bearing Spacers are shown, these locate inside the Spherical Bearing itself, after the insert is pressed into the trailing arm. The spacer lip provides a very slight press fit to make installation of a completed trailing arm into the subframe easier. For those of us who make up literal terms in our minds, we would call this a “snap” fit.

Following the zinc plating process, we laser mark our Bearing Sleeves with our brand and part number. It is our hope that no one hood-winks our product, but in the case that they do, and fate leads them to read this post, please send us a thank-you card with a gift certificate to your favorite restaurant.

Finally we press-in the Spherical Bearing used in these inserts. This bearing is a heat-treated, lined, motorsport grade bearing. As a safety precaution, a heavy-duty spiral lock retaining ring is installed against the exposed face of the bearing.

If the day comes, where the Spherical Bearing has surpassed its useful life and needs to be replaced, the entire sleeve need not be removed from the trailing arm. Removing the retaining ring and utilizing an appropriate bearing puller, these bearings can be easily replaced. Upon request we can provide replacement bearings with new retaining rings, as well as a bearing install tool.

As an end-note, this product is simply an introduction to the rear end work we have in the cauldron for the e30 chassis. Stay tuned in the coming weeks to find out what we have been up to.

Back to blog list

About the Author