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Discussion Starter · #1 ·
I'm in the process of installing Bilstein sports with my H&R sport springs. I just completed the driver's side and noticed that the bilstein piston is a few inches longer than the stock Sachs-Boge strut. As a result, the spring does not seat snug between the spring perches with the bilstein strut. There's quite a bit of looseness with the spring at full uncompressed length.

Has this been everyone else's experience? I double checked the part number on the bilstein struts and H&R springs to confirm they are the appropriate part for the car. If the Bilstein sport's piston length is so much longer than the stock Sachs shock, I can't imagine how the Bilstein HD's would sit. Of course, with the strut assembly installed and the weight of the car compressing the assembly, the spring will sit snug and compress between the spring perches.
 

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Contact H&R. I've never seen a properly assembled strut where the spring was not fully seated on the perches.
 

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Der Ursprüngliche....Albo
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This sounds like you have a defective strut. I did not have this problem with my Sport Struts that I installed a couple of weeks ago. I didn't note the difference in strut length, but it was certainly not longer than the stock one.
 

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Discussion Starter · #4 ·
Interesting, it sure sounds like these struts came without an internal stop of some sort, allowing the piston to extend several inches longer than the stock units. And what are the odds of me getting 2 identical defective front struts?
 

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Interesting, it sure sounds like these struts came without an internal stop of some sort, allowing the piston to extend several inches longer than the stock units. And what are the odds of me getting 2 identical defective front struts?
Call Bilstein USA and talk to them directly. Describe the situation. Also ask them what is the length of the strut when fully extended so that you can compare. Measure your strut so you have an exact reference.

Old Bilstein are known to have had longer piston.

mw
 

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Discussion Starter · #6 ·
I talked to Bilstein, H&R, and Turner Motorsports (where i bought the shocks) regarding my issue.

The Bilstein representative did not seem very knowledgeable and gave me generic answers to my questions. When asked about why the Bilstein strut was longer than the stock Sachs sport strut he said "Bilstein has a reason for designing everything the way they do and tests every strut for fit and finish, etc

The H&R representative seemed more concerned about the increase length of the Bilstein sport strut piston and stated that he himself has the e39 with the same H&R spring and Bilstein sport strut setup. He felt that the springs should seat snug between the perches, at least by his experience and that the piston length shouldn't have been longer than the stock shock. He recommended contacting Bilstein to confirm the appropriate part number. We confirmed that I had the correct springs.

The Turner Motorsport representative seemed most knowledgeable and said that it was normal for the Bilstein sport shock to be longer than the stock Sachs strut. In fact, said that ironically the Sport piston length was longer than the HD because the internal bump stop was shorter. The looseness of the spring between the perches didn't seem to bother him either since it shouldn't be an issue unless the car was getting airborne for 5 secs with a sideways load to dislodge the spring.

I have completed the shock installation at all four corners (rears were extremely tedious!). The rear fender - wheel gap is nearly nonexistent while the front seems to have a 1.5" tire - fender gap giving the car an almost "raised front appearance". The Turner Motorsport rep said that that was probably normal and likely an illusion because of the design of the front fender arches being higher than the rears. To properly assess ride height, a different reference point on the subframe needed to be used, not fender arch.

Functionally, the shocks are working fine with the springs. The floatiness is gone, responsiveness improved, and no more bottoming out over speed bumps. The ride is firm and controlled, not harsh at all. The ride is perhaps comparable to evenly slightly better than my 330i with the Koni FSD's except on larger bumps. Cornering is sharp and flat.
 

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Wish I saw this over the weekend before I installed my sport shocks but I did not notice any difference in lenght with the oem shocks, but I did notice that they were much heavier...and rides a lot firmer, luv it!
 

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Is it possible that the Bilstein Sport is the same geometry as the BMW Standard but with different shock valving? And if so, does Bilstein HD also have the same dimensions and yet another different valving? It could be as simple as cost efficiency from Bilstein to have one strut body but different internal valving depending on application. The sport or standard springs will set the ride height.

I had incompatibility issues between OEM springs (coil spring broke) and struts on my Volvo last summer which caused the front end to look ridiculous. I did not want to go through the same procedure with my E39 so I decided to just buy the Sachs-Boge OEM sport struts for my sport-package E39.
http://granlund.homelinux.net/~granlund/img_3737.jpg
 

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Just in case you ar not aware of it; shock absorber gas spring constant and damping has to be (reasonably) matched to the coil spring constant. Otherwise you can end up with quite interesting and uncomfortable ride behavior.

If you are going to use H&R race springs, I would recommend either Bilstein or Sachs sport struts all around.
 

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Grandlun:

It's not the Gas inside the damper that is used to match the spring constant...it's the VALVING. THe gas' job is to prevent the hydraulic fluid from foaming (aeration) in most twin tube shocks, but in the monotube shock (bilstein) the gas as well as the increase in pressure plays a dual role, which isn't related to spring rate.

The Turner Motorsport representative seemed most knowledgeable and said that it was normal for the Bilstein sport shock to be longer than the stock Sachs strut. In fact, said that ironically the Sport piston length was longer than the HD because the internal bump stop was shorter. The looseness of the spring between the perches didn't seem to bother him either since it shouldn't be an issue unless the car was getting airborne for 5 secs with a sideways load to dislodge the spring
Cliff's note: A SPRING MUST SEAT PROPERLY INBETWEEN A DAMPER'S PERCH MOUNTS. NO EXCEPTIONS!!!!

This---> to have a spring that is allowed to FALL OUT of the spring perches, whether it be on the car or prior to installation, is NOT an acceptable outcome.

YOu must understand this, because if you have a working knowledge of the critical orientation of the spring, spring pad, and strut perch,
----> NOT IN GENERAL, but IN PARTICULAR, the E39, a loose spring, even at the time of install, can change the proper orientation of an e39 spring to strut, and the end result is you could have a car that sags too high, and/or the strut may stick and bind up during compression/ rebound because the spring isn't colinear with the stroke of the damper. If you look at the lower spring perch on the strut, it's not even circular...it's elliptical, with a cutout to orient the precise placement of the spring pad, which precisely positions the coil spring, a PROGRESSIVE rate spring where the size changes from one end to another, so there's a reason behind all of these particulars. Don't casually dismiss this.

Bump stop myth:
It really doesn't matter whether the bump stop is shorter or not, because that is NOT what a bump stop is designed for....it's designed to absorb forces only in the compression direction. The entire issue with a shock being too long is 100% in the opposite direction, ie rebound in the extension direction. The way to exact the right distance for a damper to fully extend is to use a "TRAVEL LIMIT" spacer, this is a spacer that is installed between the top of the shock body and the base of the moving shaft, and its function, aptly called, is to limit the amount of extension for a damper device. A damper that is too long for the overall length of the intended spring is easily corrected by simply making the proper length travel limiter.
 

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Older than old school
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Cliff's note: A SPRING MUST SEAT PROPERLY INBETWEEN A DAMPER'S PERCH MOUNTS. NO EXCEPTIONS!!!!

This---> to have a spring that is allowed to FALL OUT of the spring perches, whether it be on the car or prior to installation, is NOT an acceptable outcome.
You know, I've wondered about this. If the aftermarket springs are shorter than the factory springs, allowing the car to sit lower, how could they fit as snugly as the factory springs on full extension? You have two different spring lengths trying to cover the same distance when the suspension is fully extended. How does that work? Is the wheel travel limited by the length of the shock extension?
 

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But it's worth reading twice. ;)

:thumbup:

mw
Haahaa! I took your advice:

The way to exact the right distance for a damper to fully extend is to use a "TRAVEL LIMIT" spacer, this is a spacer that is installed between the top of the shock body and the base of the moving shaft, and its function, aptly called, is to limit the amount of extension for a damper device. A damper that is too long for the overall length of the intended spring is easily corrected by simply making the proper length travel limiter.
 

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.

If you are going to use H&R race springs, I would recommend either Bilstein or Sachs sport struts all around.
Yes, Bilstein Sports w/H&R race springs
 

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You know, I've wondered about this. If the aftermarket springs are shorter than the factory springs, allowing the car to sit lower, how could they fit as snugly as the factory springs on full extension? You have two different spring lengths trying to cover the same distance when the suspension is fully extended. How does that work? Is the wheel travel limited by the length of the shock extension?
Factory springs are supposed to be in a compressed state when the strut is fully extended. One can obviously not mount lower (shorter) springs in those struts than that they still are in a compressed state.

Otherwise shorter struts (lower spring perch) must be fitted with appropriate springs that can extend the strut completely without falling out. Adjustable coil-overs accomplish this with the lower spring perch altering ride height.
 

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No, use sport shocks that are valved for the shorter and firmer springs. You can also take a look at Koni since they are selling with a rebate right now.

I would never use regular shocks/struts with shorter springs.
 
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