Well my 530i is starting to develop the 40-60 mph shimmy on braking (usually when going downhill). Since my research here and on bimmerforums.com seems to indicate that thrust arms at a minimum need to be replaced, I've been doing a lot of shopping both on eBay, local vendors and at the major websites - bmaparts, autohausaz, pelican parts, bavauto etc.

Some vendors offer an M5 upgrade, so I'm wondering what the differences between the stock 530i suspension and the M5 suspension might be. I haven't been able to find many differences other than aluminum vs steel.