Why Do BMW 325i E36/E46 Trailing Arm Bushings Have Slits In Them
A common question we often get asked is why do the new style trailing arm bushings for the BMW E36 like the 325i, E46, E83, E85, and E86 have a slit in the casing. The answer is pretty simple.Originally designed and installed trailing arm bushings on these platforms have a solid case design. Essentially the sleeve and the bushing were one solid piece. The problem with this design in the application of the main mount for the trailing arm is the trailing arm doesn't just move on one axis. If the bushing deflected (twisted) vertically with suspension movements then it wouldn't matter to much. However, the rear trailing arm suspension in these applications moves vertically and horizontally. Essentially, the trailing arm bushing needs to allow the trailing arm to pivot around it's mounting point.
The problem with the original BMW parts is it limited the travel of the suspension slightly, the bushing would deflect too much, and then start to tear/crack. The new design with the slits in the bushing acts as a pressure relief and allows the bushing to pivot and deflect without additional binding. While the design may look odd from that of a traditional bushing, the intent is to prevent the bushing from binding. The split design also aids in installation slightly as well.
Written By: Gareth Foley
Gareth is the BMW Catalog Manager for FCP Euro and has been with the company since 2012. Gareth's BMW obsession started with a hand me down E39 528i when he was 17. From this car he learned how to do his own repair work while also learning more about BMW. When Gareth was at CCSU studying Marketing he had the opportunity to go to SEMA with the college car club. This is where he developed his love of the automotive industry. Since joining FCP in 2012 Gareth has sought out to develop one of the broadest and most accurate BMW replacement parts catalog. he can be reached at firstname.lastname@example.org