Bilstein has me confused

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G03rt2
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Bilstein has me confused

Post by G03rt2 »

It goes together just fine without the collar/sleeve and rubber piece. So my question is: what is the rubber piece? An external bump stop? Is it supposed to just slide up and down on the shaft? The picture shows the old parts and the new parts side by side. Any help is appreciated... Again..
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tschultz
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Re: Bilstein has me confused

Post by tschultz »

It looks like your new perch is on upside down. Also that rubber looks like a newer version of the bump stop-- I haven't bought new ones in about 3-4 years, but I know the naming convention changed lately.
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Brucey
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Re: Bilstein has me confused

Post by Brucey »

the perch is indeed on upside down and will never work like that.

You appear to have some extraneous parts and in addition you appear to have not enough parts to make a working shock absorber.

You need all the parts in this diagram

http://2009.bmwfans.info/parts/catalog/ ... ing_strut/

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and none of the ones that are not. For a standard ride height 82- 635CSi all the pns are correct apart from those for the springs and shock absorber.

In particular you need #11 'damper' which is your bump stop. Without this your protection tube will have nothing to mount on.

If you have lowering springs there which drop the car more than 3/4" I think you should have # 11 from here
http://2009.bmwfans.info/parts/catalog/ ... ing_strut/

instead, i.e.
33 52 2 225 023 (for M635CSi)
rather than
33 52 1 124 573 (for standard 635CSi, most E28 etc)

if you use -573 in a lowered car (as indeed BMW did in E28 M535i) then you will get a rather jiggly rear suspension action.

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duracel79
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Re: Bilstein has me confused

Post by duracel79 »

The large rubber and washers appear to be the one used on Early E9/2002 rear shock mounts.

Items 9/10/11 here:
http://2009.bmwfans.info/parts/catalog/ ... h_parts-2/
G03rt2
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Re: Bilstein has me confused

Post by G03rt2 »

Thanks for all the replies. Especially pointing out that the perch is upside down, cupping upward just seemed like the proper way to do it, but it makes sense to have the chamfer on the inside. I should mention this is for an e12 based car. The "bump stop" metal collar and existing dust boot are probably going to get left out of the equation. I'll take pictures and post them when I get home, but the existing dust boot is pointless with the new setup, and the bump stop they supplied will never work unless it's supposed to freely float on the shaft.
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Brucey
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Re: Bilstein has me confused

Post by Brucey »

E12 parts are similar; you can find a similar illustration on the ETK.

My advice is do not under any circumstance leave off the BMW bumpstop and the protection tube!

The bumpstop goes at the top of the shock shaft and the protection tube mounts on the lower edge of the bumpstop. The upper part of the shock absorber body slides within the protection tube.

Without these parts fitted the car will handle like crap ( the bump stop is working in most corners) and water will pool around the shock shaft where it enters the body and will cause the shock absorber to fail.

This is how E12 shocks should look (without the springs fitted)

Image

No idea what the crappy little rubber cone part is for; if it is a bumpstop it looks as if it will stop the BMW bumpstop from working properly. BMWs have been fitted with identical bilsteins for about 40 years without that part fitted.

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G03rt2
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Re: Bilstein has me confused

Post by G03rt2 »

Brucey,

That's an interesting and very helpful picture. All that was left of my bump stop was that small piece of brittle rubber. Which explains why the boot/cover was floating around the bottom of the shock and seemed useless to me. Now that I see how it's supposed to go together it makes more sense. I don't think I'll be able to use the oem bump stop since I am using HD shocks. (Yes, I know to use the sports with lowering springs but HD is all that was left). I'm going to look for an alternative bump stop that is shorter.

And again, thank you for that picture
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Re: Bilstein has me confused

Post by Brucey »

if the protection tube is the same pn between E12 and E28 then you could use the shorter M635CSi bump stop pn I detailed above.

BTW the shock body is exactly the same length between HD (B6) and sports B8 shocks, it is the shock shaft which is a different length. This means that you just need a shorter bump stop, shorter by the amount of lowering (roughly), thus the M635CSI bumpstop should be fine.

If you use lowering springs with HD shocks there are two risks

1) that you won't be able to adjust the ride height correctly (then again there is some overlap between the perch positions on both types of shock, so you might get lucky). The cure for this is to machine fresh grooves into the shock body or (easier) obtain or modify the perches to give the height you want.

2) that the springs will dislocate when the suspension is on full droop. If the springs are slack when the shocks are out of the car, you are definitely in the poop. There is a small rubber top out buffer inside the shock, so when the shocks are in the car, they often extend another 1/4" or so when the car has the weight off the wheels. This being the case, it is a good idea if the springs are compressed at least 1/4" or so when they are mounted in the assembled shocks (at the setting to give the correct ride height, obviously).

FWIW the OEM bumpstops are made of polyurethane foam and they last 5-10 years before they crumble and need to be replaced. It looks as if you could shorten the long standard bumpstops, but if you cut the top off they are no longer sung on the shaft, and if you cut the bottom off you lose the grooves that locate the protection tube. I suppose you could recut the latter if necessary.

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G03rt2
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Re: Bilstein has me confused

Post by G03rt2 »

Just an update. I wish I would have taken pictures since this is going to be hard to explain. I wanted to finish the project so I went to the local auto parts store, had them bring out a few bump stops and purchased the one that I thought would work best. It's now "floating" on the shaft since there is nothing to secure it to. I then put the large washer on that was provided by Bilstein and put the dust cover on over that, and it actually fits so the cover stops at the very top of the cover, so the cover covers about 2/3's of the shaft.

With the new lowering springs everything rubs since I have oversized tires on this car. (New tires & rims on the way). So I haven't been able to put it through it's paces and see if anything bottoms out or if the bump stops will get snagged.
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Brucey
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Re: Bilstein has me confused

Post by Brucey »

If you want the OEM protector sleeve arrangement to work, you really you need to buy the OEM BMW bump stops, not random stuff from the local parts store.

But having said that you can make bump stops a tighter fit on the shaft by winding tape round the shaft in some cases.

You can also shorten the OEM bumpstops at the bottom, and recut the groove to locate the protector sleeve.

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G03rt2
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Re: Bilstein has me confused

Post by G03rt2 »

I really just wanted something there for the added protection, and since I would have to cut the oem ones (which would make them unable to hold up the dust boot), I chose to go random. I like the idea of "clamping" it on with tape though and I also like the idea of cutting a groove in it for the dust boot. Since the tires don't fit I haven't had a chance to really test the setup, but when I do, I'll put it through it's paces and give everything a look over to see where the long term issues might arise.
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Brucey
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Re: Bilstein has me confused

Post by Brucey »

G03rt2 wrote: Wed Mar 21, 2018 7:41 pm I really just wanted something there for the added protection, and since I would have to cut the oem ones (which would make them unable to hold up the dust boot),
Perhaps you have misunderstood what I said before; if necessary you can trim the bottom of the OEM bumpstop and recut the groove that supports the dust boot without great difficulty. The top of the bumpstop is intended to be a tight fit on the shock shaft; you cannot trim the top without making the bump stop loose on the shaft.

The idea of using tape is to make the shock shaft slightly larger in diameter so that a slightly slack bump stop becomes snug again on the shock shaft. This works on most E24 rear bilsteins because the topmost inch or so of shock shaft never goes inside the shock body.

If you want a setup that is plug and play, just buy the OEM parts that I listed for M635CSi and get the (E28 type) protection tubes that fit those too. The bump stop will be the correct length for lowered suspension and the protection tube will fit correctly.

Without labouring the point (again....) the bump stops are an integral part of the suspension setup on an E24; they start to affect the suspension in all kinds of normal driving situations, not just on full bump. If you fit something else then not only are you likely to leave the protection tube flapping up and down uselessly, but you will have a car that almost certainly handles badly too.

Bump stop too short, too soft, or missing = understeer when you are trying hard (not what you bought a rear wheel drive car for....) and nasty bottoming behaviour

Bump stop too long or too stiff = nasty jiggly ride and too much oversteer

Bump stop has abrupt change in stiffness (as most aftermarket ones do) = abrupt transition from understeer to oversteer

I would advise anyone with an E24 to go for a drive in a car with standard suspension settings (including recently fitted standard bump stops) before they try and 'improve' the suspension on their own car. The chances are excellent that the handling was bloody awful before because your standard parts were old and knackered, rather than BMW didn't know how to make a car that went round corners..... :roll:

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zinnocoupe
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Re: Bilstein has me confused

Post by zinnocoupe »

As always Brucey, very informative posting here. And great pics. I’ll be doing this in the near future on my 77 e12 and this has been agreat help. Cheers
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