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Join Date: Jan 2008
Location: Pismo Beach, CA
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"Softball" Control Arm bushings
Everyone has heard about the spherical ball joint upper control arm bushings being used in the E24/E28/7 series/8 series. Typically these are solid metal machined bushings with a spherical ball joint installed. They are a considerable improvement over the standard BMW bushings, modified 750 bushings, and even the solid urethane parts. In E39 M5 circles these are often called "monoballs" (aka Dinan). I call them "hardballs" because they have no give and can transmit a lot of harshness and road noise into the cabin. I am also concerned that over the long run, these will induce metal fatigue and cracking in the mounting sheetmetal in our cars, particulalry the older 80's vintage vehicles.
Some years back (mid to late 80's), Frank Fahey invented a considerable improvement over the "monoball" or hardball design. It consisted of a layer of urethane bonded between two metal sleeves. The outer sleeve pressed into the control arm, and inner sleeve was used to mount a spherical ball joint, as in the monoball. The advantage was you had some cushioning of shock from the front axle to the body, but still had the suspension control of the monoball construction. He also built monoballs for his race cars but found them too noisy for street use. He stopped production in the late 80's as popularity of those cars decreased.
Fast forward to 2007/2008, I resurrected the "softball" design after considerable discussion with Frank. I was sick and tired of replacing control arm bushings every 30k mi or so. So I built about 5 pairs of bushings as prototypes and sent a few pairs to Frank for installation in his customer cars for long term testing (even though he still has customers with his original 80's version that are going strong) as we wanted to be sure the urethane would hold up. My prototypes were built with the latest in urethane bonding technology which was not available in Frank's early products. I have had a set in my Dinan E24 M635 since 2007 and they are going strong. I have about 40K mi on them and the only issue I have had is a bit of stiction noise (due to the tight tolerance of the Aurora bearings I use). The problem was resolved with a little teflon grease on the ball (and no need to pull the arms from the car!!!). I found out Frank is using one set in his 840 and is very happy with the results.
I am considering cranking up production if there is enough interest. I also am planning to extend the design to the E39/X5 vehicles as well. Any feedback would be appreciated.