About six weeks ago, we returned from a trouble-free 2200-mile road trip around Europe. Nothing went wrong, nothing broke, nothing happened that should not have happened. However, not 300 miles later, I found myself with this:

Thanks to roads here in the United Kingdom sporting potholes that rival the Moon’s larger craters, the offside lower control arm on the E39 met an untimely end. The degree of damage in such a short period of time was truly astounding – six weeks ago, the car was completely stable at 140mph on the German Autobahn, where last week along the M62, I found it borderline scary to drive at half that speed. You can see below just how knackered the ball joint is.

Though hardly excited about the idea of replacing something that otherwise would have had many more miles in it when used on properly maintained road surfaces, I was relieved that it was only the lower control arm that broke. The E39 uses three arms to control the front hub: the lower control arm, a traction arm, and a track rod. The outer two are easy enough to replace, but the traction arm basically requires taking the whole assembly apart. The lower control arm happens to be both the least expensive of the three, and the easiest to replace.


It should take little more than half an hour to replace the arm. First, remove the 22mm nut from the ball joint and separate it from the hub with a ball joint splitter. Then remove the fastener – a 16mm bolt with an 18mm nut – that connects the arm to the subframe. Mount the new arm to the subframe loosely, fasten the ball joint to the hub, and then preload the front suspension and torque down the subframe fastener. As usual with suspension parts, it is a good idea to do both sides at the same time.

A quick test drive confirmed that stability had returned. And while this was all a bit of an annoyance, I’m glad it was not a broken coil or anything worse.

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