superfast

I have an 02 CL500 for about 4 years now. I'm lucky that the previous owner had the dealer removed/replaced most of the ABC components i.e. new tandem pump, valve blocks, pressured hoses & filters so I have no issue with it. I can leave the car sits for over a month & it's not sagging at all. My only issue w/ the car is I can hear a low, constant thumping/rumble noise (not rattle as car is rock solid) whenever car is driven on bad roads & it's driving me crazy. The previous owner had upgrade the CL w/ staggered 18" CLS wheels & Continental ContiProContact tires. At first, I thought the noise was coming from the tires so I've replaced them w/ another sets of Nitto 555 Extreme ZR tires but the noise still there. I thought about the ABC accumulators as they're part of the suspension so last week, I went ahead & replaced all 4 even though I've found out only 1 of them (front left) was bad after removal. Since the ABC is a closed loop system where the fluid is re-circulating back into the reservoir via the return line, I've only topped it off & didn't do a complete flush nor a rodeo as the fluid is still very clean. Guess what? The noise is still there. Do any CL owners out there ever experienced this type of noise on your cars? Please advice. Thank you very much. John

Btw, Merry Christmas & Happy New Year to you & your family. Have a safe holidays season.