In Reply to: Do you mean your Bilsteins had design flaw? posted by Dave R. 91 35i, 71 02 on December 15, 2000 at 22:11:30:
I have the same "Thud" sound over bumps & rough roads. Spoke to rep at Bavarian Auto & he sent out new Bilstein Sport struts, he also said the the new struts have a new double valve so it should be better. Will install new struts next week.
My 91 525i has the Bilstein Sport and H&R lowering spring combo and I experienced a similar noise, "thud" sound, you are describing after the suspension components where installed. The noise occured when going over uneven pavement, over bumps, dips, etc. very annoying! Since I did not replace my strut tower mounts I blamed that component and went ahead and changed them. No luck, noise still there. Ultimately my mechanic went nuts trying to locate the problem with no luck. We called Bilstein to verify if we had the right stuff - we did! He checked all other parts like the thrust arms, replaced spring pads, etc. - all ok. So what is it? The last thing we where going to do was to replace the entire strut housing - the parts where ordered - AND as I waited for them the noise stopped, just like that! Maybe the shocks needed a "settling" period, that's my only guess.
As previously mentioned, a stiffer suspension will loosen up other parts. Adding the springs will make the car even tighter and harsher. You may have to troubleshoot several items before finding your problem. Hopefully your "thud" will go away with time as mine did.
‘91 525i 5-sp
I have been told here that the sports Bilstein Shocks should go with the lowered springs. My mechanic told me you can do the upgrade without the lowered springs. I wanted to try the sporty feel and I went with his opinion. Todat the second day I have them on and I am hearing something in the front like something hiting against something else. (on bad roads) (on occasions) Is it becuase these shocks are not the right kind? Is the sports shocks-lowered springs a must, or recommended.