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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > Suspension | Brakes | Chassis > Used shocks behavior



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      11-20-2011, 09:07 PM   #1
DaanBMW
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Used shocks behavior

I was looking at a set of used dampers, and while the struts had the springs on, and I couldn't really tell if they were working, the shocks were worrying to me.

These shocks were Koni yellows, so they should act the same as Bilsteins I'm familiar with (seee below), but they seemed "dead" - meaning that one was slowly push out a mere 1 inch or so after being pushed in all the way, while the other would not push out at all. The rod would not move freely or anything when pushed by hand, so there was dampening in both directions, but I have no idea if that is enough to deem the shocks as working. Also the adjustment seem to work as well as far as I could tell, but obviously this is just a qualitative assessment, since I can't feel how much different the dampening really is but the dampening did stiffen/loosen when turning the pushed-in rod.

The only shocks I ever had were brand-new Bilsteins, and they had a tape over the rod which when removed the rod would be pushed out by the pressurized gas. And when pushed in the rod would push out right away, all the way out of the tube.

So were the Koni dead then ? or is this how dampers are after use, i.e. they don't push out anymore like they do when new ?

Thanks for the input.
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      11-20-2011, 09:30 PM   #2
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Quote:
Originally Posted by DaanBMW View Post
I was looking at a set of used dampers, and while the struts had the springs on, and I couldn't really tell if they were working, the shocks were worrying to me.

[...]
The BMW performance shock and strut (7,000 miles on them) I have here push up slowly to full extension after I push them down. I have no idea whether pushing back is a sign of a happy shock or not.

Bilstein monotubes have significantly more pressure, and it does push the piston out.
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2007 328i ZSP. M3 suspension: custom valved Bilstein shocks, Hyperco race springs, M3 lower control arms front and rear, M3 sway bars, and M3 subframe bushings. E46 front guide supports. Euro tail lights.
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      11-30-2011, 03:25 PM   #3
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Quote:
Originally Posted by DaanBMW View Post
I was looking at a set of used dampers, and while the struts had the springs on, and I couldn't really tell if they were working, the shocks were worrying to me.

These shocks were Koni yellows, so they should act the same as Bilsteins I'm familiar with (seee below), but they seemed "dead" - meaning that one was slowly push out a mere 1 inch or so after being pushed in all the way, while the other would not push out at all. The rod would not move freely or anything when pushed by hand, so there was dampening in both directions, but I have no idea if that is enough to deem the shocks as working. Also the adjustment seem to work as well as far as I could tell, but obviously this is just a qualitative assessment, since I can't feel how much different the dampening really is but the dampening did stiffen/loosen when turning the pushed-in rod.

The only shocks I ever had were brand-new Bilsteins, and they had a tape over the rod which when removed the rod would be pushed out by the pressurized gas. And when pushed in the rod would push out right away, all the way out of the tube.

So were the Koni dead then ? or is this how dampers are after use, i.e. they don't push out anymore like they do when new ?

Thanks for the input.

The brand new Koni yellows I bought for my E36 M3 acted the way you described -- appeared 'dead' compared to other brands of gas-pressurized shocks I had played with in the past. My guess is that a more forceful impact changes how they respond, but since I have no idea how they are designed internally, this is purely speculation.
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      11-30-2011, 03:49 PM   #4
CALWATERBOY
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Quote:
Originally Posted by DaanBMW View Post

So were the Koni dead then ? or is this how dampers are after use, i.e. they don't push out anymore like they do when new ?
Your local suspension guru will be able to bench test shocks and print results w/curves. Have him check shocks & springs to see if good match.

Used yellows....where'd you come across 'em?
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      11-30-2011, 04:53 PM   #5
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Quote:
Originally Posted by SmellyGreek View Post
The brand new Koni yellows I bought for my E36 M3 acted the way you described -- appeared 'dead' compared to other brands of gas-pressurized shocks I had played with in the past. My guess is that a more forceful impact changes how they respond, but since I have no idea how they are designed internally, this is purely speculation.
Really, brand new Konis weren't pushing the piston out ?? Wow, that is some difference to the Bilsteins...

This is very useful info, appreciate the input !
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      11-30-2011, 04:59 PM   #6
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Quote:
Originally Posted by CALWATERBOY View Post
Your local suspension guru will be able to bench test shocks and print results w/curves. Have him check shocks & springs to see if good match.

Used yellows....where'd you come across 'em?
It's not that easy to find a shop that properly test shocks... plus you don't want to spend money for each shock you find used locally... it was a dude selling here in Portland.
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      12-06-2011, 08:37 PM   #7
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Quote:
Originally Posted by SmellyGreek View Post
The brand new Koni yellows I bought for my E36 M3 acted the way you described -- appeared 'dead' compared to other brands of gas-pressurized shocks I had played with in the past. My guess is that a more forceful impact changes how they respond, but since I have no idea how they are designed internally, this is purely speculation.
+1
I think my Koni yellow act like that when I got them brand new.
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