Well, I plan on trying the water injection thing this weekend to get rid of this increasingly annoying piniging in my M50. But in the meantime, I have a new problem to attend to: On the freeway, the 525i has recently developed a low rumble, as though I were driving over a freshly grated road or rougher surface. I drive over these surfaces daily and know they are generally pretty smooth. The rumble usually takes place at 65-70mph and lasts about 10-15 seconds. It's only happened 3 times. First time it occured, I thought either they had done some work on the road or I had developed a flat, but the car handled the same--no pulling to one side or anything like that. I tried taking the car out of gear and letting the engine drop to idle; the rumble went away the first time, but not the most recent time. I don't know if this is a suspension, bearing, or tire issue. Could it be the guibo or center baring? Last time I checked that area, all looked fine.

Also, the parking brake seems weaker in the past couple weeks. I plan on adjusting it this weekend, but wonder if there is a correllation between this and the rumble.....perhaps it catching or engaging when it's not supposed to.

Any thoughts? I can't be the only one who has experienced something like this.

Thanks in advance,
BennyM