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Go Back   E46Fanatics > Tuning & Tech > Suspension & Braking

Suspension & Braking
Have some questions about suspension or brake setups for your E46 BMW? Get all your answers here!

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Old 04-19-2013, 12:57 PM   #1
katu
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Koni FSD & Eibach Prokit *Bump Stops!?*

I purchased the Koni FSD & Eibach Pro-kit damper/spring set and need some clarification when it comes to the bump stops.

I have already installed the front end parts (struts/springs/endlinks/reinforcement plates) and I ordered the following bump stops to replace the old ones:

http://www.oembimmerparts.com/produc...92-46-8e46.htm - Part#31306757046 (for the sport suspension).

I was planning to install the rear end parts next week and I noticed the rear Koni shocks already come with the bump stops (the fronts did not), so I e-mailed Koni to see if they recommended using these or going OEM.

My response from Koni:

"Yes you will need to install bump stops on the front dampers, in many cases the OE stops can be used, but will need trimmed due to the fact you are lowering the vehicle. Also the black dust cover stays on the rear shocks as well, and already have the necessary bumpstops installed."

Since I have already installed the front end parts the underlined part of the e-mail concerns me. I would need to redo everything in order to cut the new bump stops I had installed. From memory, I believe the new bump stops were almost identical in height to the old bump stops I took out.

After inquiring further with regards to recommended bump stop height, I was told I would need to contact Eibach. This is fine and I will contact them but I was curious if anyone who has installed Koni FSD / Eibach Pro-Kit springs has run across this issue. What was the result?
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Old 04-19-2013, 01:12 PM   #2
Alex323Ci
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when you cut the bump stops down its just to make them shorter when lowering. so you don't hit them as soon. if you're going the same basic height then your previous ones are likely the same length. It's more for when going lower and having a tall suspension. when you trim the bump stop its when you cut a ring off allowing more travel.
old bump stops often deteriorate and crumple over time. aways nice to replace if you have opportunity.
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Old 04-19-2013, 01:13 PM   #3
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*sorry I have not used your combo and have no first hand account of what to expect.
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Old 04-19-2013, 01:26 PM   #4
katu
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Quote:
Originally Posted by Alex323Ci View Post
when you cut the bump stops down its just to make them shorter when lowering. so you don't hit them as soon. if you're going the same basic height then your previous ones are likely the same length. It's more for when going lower and having a tall suspension. when you trim the bump stop its when you cut a ring off allowing more travel.
old bump stops often deteriorate and crumple over time. aways nice to replace if you have opportunity.
Thanks for your reply. I do understand the idea behind cutting the bump stops, but I guess my real question boils down to performance. Is my current (non-cut) bump stop going to limit travel and hurt performance when I autocross the car?

With the front end already done it would be a pain in the ass to redo everything just to cut the new bump stops I have already installed. I await a response from Eibach for more info...
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Old 04-19-2013, 01:45 PM   #5
jdstrickland
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I put H&R Sports and Koni shocks/struts on my E36 with the OEM bump stops, and no worries. I don't know how low your setup takes you, but the H&Rs dropped my car about a 1.5 inches. The bump stops just prevent metal on metal contact, and they are really very soft compared to other bump stops that I have seen used on other cars, so if they are long by an inch there should be no real problem.

If you understood the implication of the longer stops on the shorter springs, then an avoidance strategy would make sense -- shorten the bump stops for the short springs -- but I see no reason to take the car apart just to shorten the bump stops since you already have them installed.
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Old 04-25-2013, 08:25 PM   #6
katu
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After trying to get a hold of Eibach for almost a week I finally have an answer verified by their R&D department.

You do *NOT* need to cut/trim the front or rear bump stops. All is well now.

FYI This is regarding the Koni FSD (2100 4006) and Eibach Pro Kit (2067.140).
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Old 04-26-2013, 01:03 PM   #7
TT330i
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As a side note, I'm pretty sure the OE bump stops for sport suspension are shorter than the non-sport, so non-sport OE bump stops may still need to be trimmed
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Old 04-27-2013, 06:33 PM   #8
drumsauce
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I have this set up (fsd/eibach pro kit) and from my research, and as you have learned from Eibach, you do not need to cut the bumpstops. My understanding of the e46 suspension is that is uses the bumpstops as part of the spring rate. Even m3's stock only have about 1/2" travel before they contact the bumpstops...so basically the bumpstops are used to increase the spring rate. This is much different from many other car manufacturers in which they use the bumpstop as a last resort to protect bottoming out. This is a great set-up. Enjoy!
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