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Shock stem machining

Posted by camdenthrasher 
camdenthrasher
Camden Thrasher
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BMW 2002


Shock stem machining
October 24, 2017 04:10PM
Hello guys.

I'm currently building an offroad-y BMW 2002 and made a slight mistake while sourcing some larger/longer Bilstein strut inserts. Tthe upper stem/thread are of 19/18mm diameter but the currently the only camber plates being made for this car accept a 14mm diameter. The camber plates I have will not accept a larger bearing so my only remaining option is to have the stems turned down to the smaller size and have a new thread cut.

Has anyone here done this before, or have cut their own threads into the blank stems that Bilstein sells as part of their Universal Motorsports Strut? I hesitate to just take this to a random machine shop if they aren't super familiar with removing the chrome insert tube from the body and not damaging that chromed surface while it's chucked in a lathe. If someone here has the capability of doing this I'd be interested in talking about it with them.

This snafu is a big hold up right now for getting my coilovers built.
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Pete
Pete Remner
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Re: Shock stem machining
October 24, 2017 07:17PM
Why not use a proper strut top instead of a camber plate? So you might have to alter the strut tower, have to drill 3-4 new holes, so what?



Pete Remner
Cleveland, Ohio

1984 RX-7 (rallycross thing)
1978
Silence is golden, but duct tape is silver.



Edited 1 time(s). Last edit at 10/24/2017 07:18PM by Pete.
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Robert Culbertson
Robert Culbertson
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Re: Shock stem machining
October 24, 2017 08:14PM
^Yup.
19mm is REALLY close to .750in. It'll actually give you a few thou of slip if you used a COM/spherical bearing.

New project, make your own COM bearing top mounts using a steel plate and a spherical bearing cup. Welder required.

But to answer your question, yes they can be machined.
Let the machine shop know that it's a thin chrome-plated tube. Either aluminum soft jaws or brass shim-stock under the steel jaws works well.
Save yourself some $$ and remove the insert yourself.
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camdenthrasher
Camden Thrasher
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BMW 2002


Re: Shock stem machining
October 24, 2017 10:59PM
By
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Robert Culbertson
Robert Culbertson
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Re: Shock stem machining
October 25, 2017 01:45AM
Quote
camdenthrasher
By

Thanks for stopping by!
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camdenthrasher
Camden Thrasher
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BMW 2002


Re: Shock stem machining
October 25, 2017 07:46AM
Ha, I don't know what happened there. Tried to post from my phone but that obviously didn't work.

When you say a "proper" strut top, are you meaning something that's just non adjustable? Of course thats possible, however in any case I still need to correct for the pretty serious positive camber caused when raising the vehicle up about 1.5". I don't have the suspension completely built at the moment, so I'm sure exactly the amount of camber I need to correct for and thus the adjustability of the camber plates was attractive? Or did you have another reason for suggesting this? Im no expert in this field and half the reason for this project was for me to learn so I'd be curious as to your reasoning.

My fabrication capability has been greatly reduced at my current residence (basically none) so for the time being anything I want to have built is going to have to get outsourced and paid for. I figured some simple lathe work would be less cost to me than someone designing and building a full new strut top mount. Maybe I'm wrong about that

A COM-12 bearing would fit this shock stem (At least that's what Bilstein told me after I realized this mistake) but checking the outer dimensions of that spec, I couldn't fit that into the existing camber plates I have, it's just too large.
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Ascona73
Bob Legere
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Re: Shock stem machining
October 25, 2017 03:39PM
A few months back I prepped a set of the 46 mm Bilstein motorsports struts for a friend of mine. They come with a raw, unmachined top pin so they had to be machined regardless. No problem having a local shop do the work, turning them down and threading them.

As it turns out I also had to make my own camber plates and rear top mounts, so I had the pins machined to it a common 3/4" bearing.









Opel is a 4-letter word...
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john vanlandingham
John Vanlandingham
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Re: Shock stem machining
October 26, 2017 11:17AM
Quote
Ascona73
A few months back I prepped a set of the 46 mm Bilstein motorsports struts for a friend of mine. They come with a raw, unmachined top pin so they had to be machined regardless. No problem having a local shop do the work, turning them down and threading them.

As it turns out I also had to make my own camber plates and rear top mounts, so I had the pins machined to it a common 3/4" bearing.

Bob, the struts measure 50mm on the OD.
Bilstein ad department cannot measure.
The internal piston is 46mm dia., but most people don't disassemble them and measure it, so that leave the OD..
Their smooth bodied normal circle track shocks are in virtually the same things--50mm body, 14mm rod and they call them "2 inch body"

2 inches as we all know even without doing the math is 50,8mm.

I have spoken with the service competition shop guys a number of times suggesting that they clear up the confusion they create...ad dept is the answer..
If they can't keep it straight, at least we can try.



John Vanlandingham
Sleezattle, WA, USA

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john vanlandingham
John Vanlandingham
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Re: Shock stem machining
October 26, 2017 11:34AM
Quote
camdenthrasher


When you say a "proper" strut top, are you meaning something that's just non adjustable? Of course thats possible, however in any case I still need to correct for the pretty serious positive camber caused when raising the vehicle up about 1.5". I don't have the suspension completely built at the moment, so I'm sure exactly the amount of camber I need to correct for and thus the adjustability of the camber plates was attractive? Or did you have another reason for suggesting this? Im no expert in this field and half the reason for this project was for me to learn so I'd be curious as to your reasoning.

My fabrication capability has been greatly reduced at my current residence (basically none) so for the time being anything I want to have built is going to have to get outsourced and paid for. I figured some simple lathe work would be less cost to me than someone designing and building a full new strut top mount. Maybe I'm wrong about that

A COM-12 bearing would fit this shock stem (At least that's what Bilstein told me after I realized this mistake) but checking the outer dimensions of that spec, I couldn't fit that into the existing camber plates I have, it's just too large.

The "industry standard"---what I have seen on works cars overseas...for the top bearing is a 22mm ID bearing
22mm is .866"...,
Its always a "high misalignment bearing" looks like this


If we just look at Pegasus for a 7/8"---which is .875" or one red cunt hair bigger, the cost is

Quote

3072-14G
Condition: New

High Misalignment Spherical Brg, 7/8 x 1.75, Grumman Groove

1 to 3: $119.99
4 & up: $110.59
Not In Stock
notify me when available

They way others do it is a upper pin--and upper spring seat to match--a straight 20mm pin yay long and threaded--at top like the fat one on the left


What I do is make a sleeve with a shoulder that is 20mm ID and .875" OD..so when the sleeve is in place, you have the shoulder just like in the piccie



But costing around $100 less per bearing...

That is how to save money and go racing..
Undersized bearings wear out in no time plat..They are penny-wise and pound foolish.

Now let me ask: what travel and damping to you get?
What springs are you thinking...this is for a 2002 thing--with round taillights i assume.

What are you planning in the rear to balance this front?

The final thing, have you gotten any firm prices on machining the tops yet?



John Vanlandingham
Sleezattle, WA, USA

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www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.
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camdenthrasher
Camden Thrasher
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BMW 2002


Re: Shock stem machining
October 26, 2017 10:38PM
Hmm. Tried posting a long response from
My phone but failed again.



Edited 4 time(s). Last edit at 10/26/2017 10:40PM by camdenthrasher.
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john vanlandingham
John Vanlandingham
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Re: Shock stem machining
October 26, 2017 11:58PM
Quote
camdenthrasher
Hmm. Tried posting a long response from
My phone but failed again.

Not sure but you could also use the phone the other way..Instead of typing with it, you "tele-phone" with it..People did that for I dunno over 100 years and it worked pretty good, and really actaully much better than typing and waiting hours or days for a response--which might just be "what do you mean ALBATROSS?"



John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.
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camdenthrasher
Camden Thrasher
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BMW 2002


Re: Shock stem machining
October 30, 2017 08:13AM
Sorry, Haven't had a appropriate time for a phone call.

This won't be a race car, rather something for me to have fun on some trails or out in the desert in my free time. Something like Safari rally style, big(er) tires, a little lift. So....ultimate strength may not be the most critical thing as I'm not going to be in competition, but I also don't want to build something so weak it will definitely fail from general fun-having.

I haven't thought about the damping yet as I like to first get the height right and make sure there aren't any huge flaws in what I have in mind. The guy from Bilstein I spoke gave me a recommendation for a starting point on valving, but off the top of my head I don't recall what it was. The dampers are for a later 5 series and several other BMW varieties. 36mm piston and ~7in of travel. Without severe modifications to the control arms and wheel wells (that may be coming later) that's about all the travel I could hope to utilize, especially with the larger tire size.

Springs, I figured I would initially just start out with the stock rates. I had the front springs tested because the factory literature is incomprehensible to me. 250lbs/in in the front. I haven't tackled the rear yet. It would be a higher rate due in part to the motion ratio of the separate shock/spring setup and I likely will be keeping that design for now.

I've just recieved the shocks and the camber plates in the last week so have yet to get machining quotes from any local places. I still need to get the tool to remove the actual damper part from the yellow housing. I'd like to get a full measurement of the piece so that a shop would know how much would need to stick back into the throat of their lathe.



Edited 1 time(s). Last edit at 10/30/2017 08:14AM by camdenthrasher.
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aj_johnson
A.J. Johnson
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Re: Shock stem machining
3 days ago
Quote
camdenthrasher

Springs, I figured I would initially just start out with the stock rates. I had the front springs tested because the factory literature is incomprehensible to me. 250lbs/in in the front.

There isn't a snowballs chance in hell that the stock front mcpherson strut springs in a bmw 2002 were measured at 250 lbs/in
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john vanlandingham
John Vanlandingham
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Re: Shock stem machining
3 days ago
Quote
camdenthrasher
Sorry, Haven't had a appropriate time for a phone call.

This won't be a race car, rather something for me to have fun on some trails or out in the desert in my free time. Something like Safari rally style, big(er) tires, a little lift. So....ultimate strength may not be the most critical thing as I'm not going to be in competition, but I also don't want to build something so weak it will definitely fail from general fun-having.

I haven't thought about the damping yet as I like to first get the height right and make sure there aren't any huge flaws in what I have in mind. The guy from Bilstein I spoke gave me a recommendation for a starting point on valving, but off the top of my head I don't recall what it was. The dampers are for a later 5 series and several other BMW varieties. 36mm piston and ~7in of travel. Without severe modifications to the control arms and wheel wells (that may be coming later) that's about all the travel I could hope to utilize, especially with the larger tire size.

Springs, I figured I would initially just start out with the stock rates. I had the front springs tested because the factory literature is incomprehensible to me. 250lbs/in in the front. I haven't tackled the rear yet. It would be a higher rate due in part to the motion ratio of the separate shock/spring setup and I likely will be keeping that design for now.

I've just recieved the shocks and the camber plates in the last week so have yet to get machining quotes from any local places. I still need to get the tool to remove the actual damper part from the yellow housing. I'd like to get a full measurement of the piece so that a shop would know how much would need to stick back into the throat of their lathe.

Dear god.
What did the factory literature say?

Some of us speak other languages and numbering systems. Since it is where we learned things and is our business.



John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.
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Philippe Bellefleur
same as above
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Re: Shock stem machining
3 days ago
Like AJ says, 250 lbs/in seems kinda high given that it's a car from the 70's that weights less than modern sports cars that have softer springs than that. If they actually tested at 250 lbs/in, i would suspect upgraded springs were installed.
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