Control arm replacement

bluecoupe30!

bluecoupe30!

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This job is up next. Did a search and found how just trying to replace bushings can be a real challenge. I have 2 new control arms with bushings attached, and wonder what I am in for. Any suggestions regarding technique, pitfalls...what to watch out for? Thanks for any insights. Mike
 
With bushings already installed this job is pretty simple. Remove the very large nut on inner side of arm, nut on tension strut, cut locking wires on mount under strut, remove three bolts there. I put spring tensioners on the spring when they are compressed using the floor jack with wheel removed of course. When installing put it on tension strut first, a bottle jack helps to position inner arm to the long bolt which I do last. Hope I'm not confusing this with the 2002!
 
I was not able to find an OEM LCA but La Jolla let me know that the E12 arm is the same as the E3 and E9 and the OEM E3 andE9 bushings are still available. I built an OEM arm that cost about the same as the aftermarket stuff (o-cap). I have never compressed the springs, just raised the wheel a bit with a jack to separate the arm from the strut housing after removing the three bolts.
 
The regular control arm is 381mm, the 74 version is 402 and NLA. The e12 doesn't list the length but all three versions have different part numbers.
 
I was reading the "Autobooks" Owners Workshop manual on how to dismantle the Control arm. They suggest using a "Kukko" extractor to press the control arm ball joint from the steering arm. I am sure many others work, the one in their sketch looks massive, just wondering what may have worked for others who have successfully completed this job. Thanks, Mike
 
HB Chris said:
The regular control arm is 381mm, the 74 version is 402 and NLA. The e12 doesn't list the length but all three versions have different part numbers.
Click to expand...
Whoops I think you've got them switched around, Chris.
The 381mm length is the earlier version for '68-late 73 cars that shows NLA from BMW, pn 31121104387 & 31121104388 (superceded to 31121104389 & 31121104390)

The OCAP parts are the shortie part numbers

the 402mm length is for late'73-on cars (and the same geometry as E12 & early E24) and still listed as available from BMW 31121112011 & 31121112012
For decades the gurus said the later arms work on earlier cars, change them in pairs only, they add 1 5/8" to the front track...I still wonder about the tension rod having a different angle where it plugs into the giant front bushing on the subframe.

I also don't know if I'd want to reduce the front track on my '74 by using OCAP parts
 
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HB Chris said:
I see no difference from what you are saying dp. And the longer control arms do use a different tension strut.
Click to expand...
Uh..just that the short arms from BMW are NLA, the 402s are whats available (you posted the other way around.)

-shrug-...
 
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This is interesting information. Some time ago i replaced my control arms. On checking the part number with W&N, who supplied them, it turns out they are 381mm for a pre 74 car. Mine is a 1974 model.
Might it be that there is no difference in the length of the stabilizer bars, as if mine were indeed original (and i have no reason to doubt they wouldnt be) there has been no noticeable fitment issue with the shorter wishbones. The parts manual is confusing, and furthermore only lists one wishbone common to all models. Thank you DP for the later part numbers.
 
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The Orange parts book shows one one style wishbone, the shorter 387/388 as of 4/75 which is strange. Only the ETK will have the correct answer, RealOEM will always show what it fits today, not what it was designed to fit originally, big difference.
 
dp said:
Whoops I think you've got them switched around, Chris.
The 381mm length is the earlier version for '68-late 73 cars that shows NLA from BMW, pn 31121104387 & 31121104388 (superceded to 31121104389 & 31121104390)

The OCAP parts are the shortie part numbers

the 402mm length is for late'73-on cars (and the same geometry as E12 & early E24) and still listed as available from BMW 31121112011 & 31121112012
For decades the gurus said the later arms work on earlier cars, change them in pairs only, they add 1 5/8" to the front track...I still wonder about the tension rod having a different angle where it plugs into the giant front bushing on the subframe.

I also don't know if I'd want to reduce the front track on my '74 by using OCAP parts
Click to expand...


Decreasing the length of the control arm would probably result in a camber increase, or positive camber. Conversely, increasing the control arm length would result in negative camber, over and above the norm. The latter situation may not be ideal for tire wear but it might have a benefit in terms of handling.

As has been suggested, the "braking" or track rods are probably sized for each of the two control arm lengths so that if the wrong ones were installed, it might only be accomplished with a fair amount of force and/or by deforming the fore and aft track rod bushings. Since I have no personal experience with this, I would also guess that using the wrong sized or mismatched tracking rods would result in both abnormal tire wear and "squirrely" steering.:(






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Gratuitous pictures.:cool:

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IMG_7264-01.jpg~original


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1972-bmw-3-0si-touring-e3-13_featured.jpg
 
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HB Chris said:
The Orange parts book shows one one style wishbone, the shorter 387/388 as of 4/75 which is strange. Only the ETK will have the correct answer, RealOEM will always show what it fits today, not what it was designed to fit originally, big difference.
Click to expand...
No, RealOEM is where I got the superceded part numbers, you need to know how to look, using YOM (year of manufacture) and looking at ALL the diagrams, BUT there's still no guarantee that any single reference will always provide you with a comprehensive picture. This is why the orange books can be helpful if you also know how to use them based upon their publishing date (thats called "context") ... it is not unlike using a 2800CS/3.0CS blue book for certain tasks, even when knowing it is not exactly corresponding to a 2nd series 3.0CSiL :-)

I regret selling off my multiple sets of orange books before realizing this

Oh, f.w.i.w. I deleted my "-30-" (journalistic notation for that's all I'll say/write) in my earlier post because lloyd, as well as HB Chris made comments that I think need to be emphasized and need to be remembered...the front suspension is a system of (over time) different parts engineered to work together, and changing "a" component in the system can alter things like handling in an unfavorable way if it is not installed with the other components it was designed to work with. The earliest E3's and E9's used a strut tower/knuckle combination that had 8mm lock bolts and used the early short arm with a corresponding geometry torsion rod. When the towers went to 10mm lock bolts, "some" cars came with short control arms and "some" came with the longer ones.
Also parts of the point I'm trying to make: on the cars with longer arms, the knuckle that bolts onto the bottom of the strut tower has a different machined angle on the mating face to keep proper camber with the bigger track...
AND part number references are helpful to a point but Chris points out (in a way) that when part numbers are superceded, sometimes the earlier part numbers are lost....
AND more than that, a superceded part number may have other mating parts that have also been superceded by the modern replacements and often enough there is no easy way to determine if a modern part number has compatability with your car's components....
AND with 45 year old cars, its not easy to tell what pieces have perhaps been changed out over the years...whether correctly or incorrectly.

You may now decide that I am just stating the obvious but this thread shows that, clearly...."we" don't all get the nuance.
 
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