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Old 09-19-2009, 10:41 PM
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bluebee bluebee is offline
Seek to understand,^Value
Location: San Jose, California
Join Date: Mar 2008
Posts: 25,236
Mein Auto: 02 BMW 525i M54 auto 130K
I had no idea my shocks were bad.

My symptoms are simple:
a) Violent shudder when ABS is activated on low-speed bumps (
b) 75,000 miles on the original Sachs 2002 525i non-sport suspension (which otherwise seems fine for me so far)
c) That's it (I do realize the Beisan Systems DIY lists other common symptoms)

What I would need (or anyone in this situation) would be to know:

1. How to definitively TEST for bad shocks & struts (aka dampers) on an E39:
- Front-wheel violent ABS shudder (this in and of itself is a definitive test, but only for the front wheels I think)
- Three-bounce test (this might not be definitive)
- Wallow while driving test (also might not be definitive)
- Leak test (this, like the ABS shudder test, is definitive)
- Uneven tire wear (this one seems really nebulous)
- ?others?

Likewise, what are the suggested tests, while you're under the car, for related suspension components:
- A test for whether the suspension springs are also bad or not
- A test for whether the RSM (rear shock mount) is bad or not
- A test for something in the suspension called a "thrust arm"
- A test for something in the suspension called a "control arm"
- A test for something in the suspension called a "sway bar"
- A test for something in the suspension called "thrust arm bushings"
- A test for something in the suspension called "control arm bushings"
- A test for something in the suspension called a "CAB"
- A test for something called a "strut guide"
- A test for something called a "protection cap"
- A test for something called "end links"
- The classic test for front wheel bearing play versus suspension parts (tire iron lever)
- Perhaps a test for ball joints (I'm not sure if they are suspension components or not)?
- Any other related suspension tests needed?

And, what do perform afterward:
- Alignment
- What else after a shock job?

2. Which shocks (for an E39 I6 non-sport suspension) to purchase & where to get 'em:
- Bilstein Heavy Duty - $$$ (see the many threads on Koni vs Bilstein)
- OEM Sachs Standard- $ (the shock the BMW designed and engineers tested in the car)

Note: If you have a sport suspension (i.e., shorter stiffer springs), additional options are:
- Bilstein Sport
- OEM Sachs Sport (
- Koni Sport (aka Koni Yellow) - $$ (assumes you have sport springs or plan on buying matching Eibach springs)
- Koni FSD - $$ (this is a "kit" of both shocks and Eibach springs)

Note: Apparently only the ricers would consider any other shocks (e.g., monroe, etc.).

Note: I did see in the threads the "opinion" that the "Boge/Sachs are garbage" and that they only last 30 to 50K miles. However, just as in brake pads, rotors, and tire selection, the evidence must be logically overwhelming to sway me from what the BMW engineers recommended and stand by legally as OEM for the non-sport suspension. I am not an engineer and I would never presume to be able to select the proper suspension system components taking into account all the tradeoffs properly. So I generally go with OE or OEM (unless there is actual concrete unassailable evidence to the contrary).

I do realize people drive differently. They have different abilities to choose suspension components. For them, saying "I like brand x" is fine, but, it's not a scientifically valid test. Basically, IMHO, the specifications either prove out one shock over the OEMs or they don't (including cost considerations). And no, sorry to break it to anyone, but, a supposed "lifetime warranty" is not a scientific test by any stretch of the imagination. Besides, I've NEVER returned an automotive part under warranty in my life ... so this is merely a marketing gimmick to me.

Likewise with the cool-yellow color or supposed chic coolness of the brand name - none of which in and of itself means anything to me. Also, I'm not likely gonna "lower my ride" or "stiffen my ride" under any circumstances other than a "real good reason" - it would just be silly to do so w/o knowing what I'm doing. All I want to do is fix my little blue BMW the right way, that's all! That simply means bringing it back to OEM condition. If I'm gonna change something, I'd need a mechanical engineering degree to figure out what that would be and I don't have that so whom am I fooling.

3. Where best to get the shocks and struts: (especially for OEM replacements)
??? ??? ???

4. The DIY for replacing shocks in an E39

See the list of DIYs below bearing in mind other suspension components might need to be tested (even more DIYs). Whew.

Here's my first attempt (so far) for the E39 to find the best DIYs:
- E39 DIY: 1998 BMW 528i COMPLETE FRONT SUSPENSION OVERHAUL (Note: Added afterward to help others find the really good DIYs!)
- E39 Beisan Systems Rear Shocks Writeup & Front Struts Writeup
- E39 Rear Suspension install

In addition to those best two, here are some really good ones:
- E39 Koni sport shock strut install
- E39 My e39 Koni FSD install and thoughts (Sachs owners especially need to see post #19)
- E39 Sport suspension in a non-sport
- E39 How to replace your thrust arms
- E39 H&R Install photos
- E39 ?let us know if you know of a good DIY not listed here?

And, here are some good ones found for other BMW models:
- E36 Rear Shock Mount DIY (E36 RSM DIY, E46 RSM DIY)
- E46 Installing Bilstein struts and shocks
- E46 Installing springs DIY

And, of course, advice on how to get any "very" special tools needed (i.e., defined only as tools you'd likely rent and not purchase outright):
- Two spring compressors
- ??? what else that we wouldn't already have or that costs more than $100 to purchase ???

Last edited by bluebee; 09-24-2009 at 02:17 PM. Reason: I will edit as needed so new information for newbies is added back
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