Good points. I'm going by what the dealer told me needed replacing last time it was in there to have the trans replaced. And I think I was confusing the thrust arm bushings with the control arm bushings. I've two 2 cars apart at the moment- reinstalling the custom valved Bilstein RSR struts on the 911 along with poly-bronze bushings, and replacing a front hub bearing on the 528. Too many repairs on the brain at the moment.

The interesting thing is that the brake shudder wasn't too noticable all winter, but once the weather got warmer the shake came back so I assume the cold air was effectively raising the durometer stiffness of the bushing's rubber.

For the shudder, I can run locally for days without an issue. And in stop and go on the highway where I'm hitting the brakes frequently even at 50+ there's rarely a shudder. But if I drive for several miles on the highway then hit the brakes, I get the usual 2 or 3 shakes of the wheel then it settles down. And if I hit the brakes right way again there's no shake. And it's worse when I'm pulling the trailer. Last time I had this problem it was the thrust rod bushings. Had them replaced (that was the 3rd replacement) and it fixed the problem.

I'm beginning to wonder if pulling a heavy trailer is contributing to the frequent replacement of these bushings. After all, when accelerating away from a toll booth or pulling long hills, all 4 tires are being driven. When unloaded the burden on the suspension isn't so bad, but with 4500 lbs (now 5800) behind me, the amount of torque being applied to all parts of the drivetrain and suspension is accentuated. And of course the opposite is true when braking even with trailer brakes. So I'm probably tugging on all those bushings far more severely than when not towing. No facts to back this up, just my thoughts.

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'04 E53, 4.4 Sport
'97 E39 528i
'86 911 Carrera, track car
'96 BMW R1100R