Probably due to BMWNA instructing dealers to covertly rotate shock towers and dealers failing to torque the bolts back to correct pressures. I had the same 'thud', which was delayed in sound and feeling when going over certain bumps, but only from the right rear. After SEVERAL complaints, a different dealer found bolts that weren't torqued completely, which they tightened, which solved the problem. Sad to say, but it's disgusting the way the company treats customers.
Last edited by dbs600; 01-12-2013 at 08:42 PM.