The other day I temporarily mounted the 500E OE wheels on my "kitted" 400/500E. While I was driving at a low speed, I began to hear a clicking/scraping sound coming from the left rear wheel/hub. I jacked up the rear of the car(safety stands and front tire blockers in place) turn on the engine, placed the tranny in N and let the wheels turn. I first thought it was the backing plate scrapping. So I first tried pushing / pulling on it while I turned the wheel. Couldn't get a good grip so I removed the wheel and placed a couple of the bolts in the hub to turn. When I did this I no longer heard the noise. Remounted the wheel and the noise came back. So now I'm thinking that it perhaps the emergency brake. Maybe its just slightly depressed but the light isn't on. I first set and then pulled the brake release but the noise was still there. Now I get scientific. I notice that the noise only occurs when the wheel is tight. So I mount the wheel loosely and begin to tighten each lug an even amount.In series, I then tighten lug one the last little bit...spin the wheel and No Noise, I tighten lug 2 the last bit, spin the wheel and no noise, lug 3 then lug 4, but this time I get the noise.Hmmmmmmm. Lug 5, I get the noise. I remove lugs 4 and 5 and replace them with the lugs that I use for OE AMG Aero wheels. The clicking sound is still there. Okay, now I'm thinking, ":Hey, maybe ai screwed something up when I mounted the wheels. So I remove one and but the AMG wheel with its OE lugs back on the car...no noise. Hmmmmmmm. "That's Odd"
Okay last step...I insert the OE lugs for both wheels into their respective wheels and eyeball measure how much stud is pertruding. There is clearly a 1/8 inch difference (longer) in the amount of stud that is sticking through on the OE 500E wheels / lugs as compared to my AMG Aero wheels/lugs. I take one of each of the lugs and place it into the hub and tighten them to where the threads show they normally stop. BINGO!! I get the noise on the OE 500E stud. I remmove the caliper/hub assy, and observe a very small hint of scrapping on the Emer.brake retaining spring. Ah Haa! I fiddle with it a little and move it back. Long story short is, The 500E hubs appear to be just a hint thicker and compensate for a difference in length of the OE 500E studs, or there is perhaps a difference in hub desigh that compensates for the difference in length. Just something to check in case you get this noise when you replace wheel sand tires on your load.