Vorshlag's new and improved Spherical Rear Shock Mounts (RSMs) for the BMW E30/36/46 are back!
The factory rubber rear upper shock mount (RSM) for the BMW chassis is a big sloppy rubber ding dong. The wear out over time and are known to be a failure point - and when they fail, they come apart completely. Even when new these have a lot of slop and "slow down" damper reactions to vertical inputs in the shocks. We can fix all of that.
Vorshlag has been making spherical RSMs for years, for a variety of chassis: Corvette, Miata, and more. But our very first design was this one, made for these BMW chassis: E30, E36/Z3 and E46/Z4 generation 3 series. We designed and built these back in 2009. They have changed colors, names and features a along the way and are now better than ever. The current version is made in the familiar Vorshlag red anodized aluminum, and they are big, beefy, and as strong as a tank. These have been machined in-house here at Vorshlag on our CNC machines starting in June 2015.
Some people are afraid to run spherical mounts at the rear shock mount locations of their BMWs, mostly from a lack of knowledge. But if you're already running adjustable camber plates up front, you already are running spherical bearings - no worries! The important part of any spherical mount is that they are sized appropriately, that they fit the shaft they are attached to properly, and they allow "no bind" articulation at the rear shock mounting point.
Rubber RSMs can fail over time - just like some of the images above show
There are three ways to make a rear shock mount for a "pin" style upper shock shaft. The OEM style rubber bushing assembly allows the proper articulation of the shock under suspension movement (it pivots at this mount) but has added deformation that you don't see with a spherical. They can also fail spectacularly. Polyurethane RSMs are too rigd and do not articulate well, causing bind, and this allows unnecessary flexing of the rear sheet metal where it mounts (this area is prone to cracks and breakage when poly mounts are used). Vorshlag Spherical RSMs do a better job than the other two - a metal spherical ball bearing that smoothly articulates with no bind. The metal tolerances are tight, for a slop-free use, which won't delay the damper inputs. Spherical shock mounts are all you see on a race car for good reason, but our design is also applicable to street use - for dual-purpose cars that see some autocross or track time.
Vorshlag RSMs are machined and assembled in-house with the same proven design and years of testing
Vorshlag RSMs use the largest spherical bearing on the market (19mm ID) - it is massive, which means it is strong. We use a U.S. made, Teflon lined, aircraft quality stainless spherical ball, stronger than the commercial grade import sphericals used in many competitors' RSM designs. The spherical bearing location itself has been raised above the shock tower, to increase overall bump travel for your rear shocks.
We have tested this design for 4+ years and they are silent, effective, and have no slop or bind in use. If you somehow manage wear out the massive spherical bearings in these shock mounts, we can rebuild them quickly and cost effectively here at Vorshlag
UPPER STEM DIAMETER: These shock mounts are designed to work with virtually any rear shock that is made for the BMW models listed. We use different upper and lower bushings (spool pieces) to adapt the big 19mm ID of our spherical bearing to the shaft sizes of the very top of the rear shock. YOU have to tell us how to build your shock mount assembly by picking the proper upper stem diameter of your rear shocks at the drop down menu below.
Virtually all shocks made for these BMW chassis (except low end Chinese shocks) use a 14mm or 16mm diameter main shaft (and even some that are 22mm) - we don't care about that. The part we need to know from you is the very top - which will have a 10mm/M10 threaded or a 12mm/M12 threaded upper shaft stem. Typically an OEM or non-adjustable shock has a 10mm shaft and an adjustable aftermarket shock has a 12mm shaft. The RSM sits on the shoulder or step where it goes from the big diameter and necks down to the small upper stem diameter. See the images below for a better explanation. If you are unsure about shock shaft upper stem option to choose, please email or call us.
Vorshlag RSM Upper Reinforcement Plate Kit: We offer a pair of our laser cut reinforcement plates we make as an optional add-on for this shock mount kit with a package savings. These plates sit on top of the shock tower and help sandwich and stengthen the somewhat thin factory sheet metal, above and below. We CNC laser cut these from alloy steel, then added a zinc chromate plating. Our design is thicker and stronger than the factory (Z3) reinforcement plates and a smart move for any street or race car - to help prevent cracked shock towers.
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