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E39 (1997 - 2003)
The BMW 5-Series (E39 chassis) was introduced in the United States as a 1997 model year car and lasted until the 2004 when the E60 chassis was released. The United States saw several variations including the 525i, 528i, 530i and 540i. -- View the E39 Wiki

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  #1  
Old 04-12-2012, 06:52 PM
Mikes530 Mikes530 is offline
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Tightening thrust arm bolts

There seems to be agreement by members of this site that you have to put the standard load on the car before re-torquing the thrust arm (upper control arm) bushing bolts. Bentley says the same. Seemed reasonable to me because there must be some rotational movement at the bushings.

Talking with an experienced BMW tech and a good BMW indie separately both said the same thing - there's no real need to put weight on the suspension when doing the thrust arm bushings. The only time that it's essential to add weight is when doing an alignment.

Are the techs wrong or is the amount of rotational movement at the bushings so small as to make no difference?
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  #2  
Old 04-12-2012, 07:09 PM
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Fudman Fudman is offline
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I won't say your tech is wrong. Several folks on this forum have failed to load the bushing before torquing and it resulted in premature bushing failure. Noone has had a bushing failure after preloading the bushing. So you make the call.
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Old 04-12-2012, 07:45 PM
edjack edjack is offline
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The load referred to in the TIS, as far as I can determine, is to put the car down on its tires, and then tighten the nuts.

An alternative, probably not useful to you at this point, is to measure the distance from the edge of the fender lip to the upper edge of the wheel, before the repair, with the car on its suspension. Then, after the replacement, when the car is on stands, put a floor jack under each front tire, and jack up until the measurement is achieved. Then crawl under and tighten the nuts. Do it for each side.

This is the alternative Mike Miller Method when a lift is not available.
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  #4  
Old 04-13-2012, 03:58 AM
TechWrench TechWrench is offline
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Wouldn't putting the front end up on a set of ramps acomplish the same thing? There would be a load on the suspension, but you could still get underneath vehicle to make final torque tightening of bolts.
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  #5  
Old 04-13-2012, 04:07 AM
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gtxragtop gtxragtop is offline
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Quote:
Originally Posted by TechWrench View Post
Wouldn't putting the front end up on a set of ramps acomplish the same thing? There would be a load on the suspension, but you could still get underneath vehicle to make final torque tightening of bolts.
Yes, with front and rear raised to the same height. IF you raise the front only to gain access, the pre-loading will not be correct since you have altered the weight distribution.

I'm 6'-2" and not a petite guy. Even with my M-sport suspension I was able to tighten up the bolts laying on the ground. I then jacked up the car to finish torquing the bolts to the proper spec. The proper procedure is to roll the car back and forth on the wheels, and then tighten. The tech that told you this was not required on a E-39 is WRONG
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  #6  
Old 04-13-2012, 06:20 AM
cn90 cn90 is offline
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Quote:
Originally Posted by Mikes530 View Post
...Talking with an experienced BMW tech and a good BMW indie separately both said the same thing - there's no real need to put weight on the suspension when doing the thrust arm bushings. The only time that it's essential to add weight is when doing an alignment.
a- Car on the lift: no good, the bushings need to be preloaded.

b- Car on ramps w/o extra loads on front seats (150lbs/each front seat).

c- Car on ramps w extra loads on front seats (150lbs/each front seat).

Th proper answer is "c".
However, if you have nobody around, I think "b" is fine too.
I use "b" and it has been 3 years, zero problems.
In fact, Honda and Volvo technical procedures call for "b".

BMW engineers are just a bit more paranoid than Honda/Volvo.

IMHO, either b or c is fine.
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  #7  
Old 04-13-2012, 04:14 PM
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Topaz540i Topaz540i is offline
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The car needs to be on the ground unless you are running polyurethane bushings.
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  #8  
Old 04-14-2012, 03:45 AM
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gtxragtop gtxragtop is offline
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Quote:
Originally Posted by cn90 View Post
a- Car on the lift: no good, the bushings need to be preloaded.

b- Car on ramps w/o extra loads on front seats (150lbs/each front seat).

c- Car on ramps w extra loads on front seats (150lbs/each front seat).

Th proper answer is "c".
However, if you have nobody around, I think "b" is fine too.
I use "b" and it has been 3 years, zero problems.
In fact, Honda and Volvo technical procedures call for "b".

BMW engineers are just a bit more paranoid than Honda/Volvo.

IMHO, either b or c is fine.
Actually, I've been mistaken also. CN90 is more correct than my last post. The TIS for the E39 states " Tighten to 110NM in normal position". Normal position is weighted as per alignment specs. I should have referenced the document before claiming I had the answer. Sorry.
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Last edited by gtxragtop; 04-14-2012 at 04:06 AM.
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  #9  
Old 04-14-2012, 12:24 PM
4thBMW 4thBMW is offline
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Thrust arm bushing preload

This subject is all detailed in Bentley's....All four wheels on flat level surface; 150 lbs. in each ft. seats; 150 lbs in middle of back sat and full tank of fuel. That's what the book says for stock bushings for final torque down. If you are doing this work you should have the book. BMW's need to be doneby the book, unless you find a good short cut...then tell us. Good luck.
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  #10  
Old 04-15-2012, 08:50 AM
Mikes530 Mikes530 is offline
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Quote:
Originally Posted by 4thBMW View Post
This subject is all detailed in Bentley's....
Yes, I mentioned this in my original post.

CN90 - The techs I spoke with were using your option "b" (no extra weight on the car) so you're confirming this if you've been fine for 3 yrs. Thanks.

Appreciate all the responses.
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  #11  
Old 04-15-2012, 12:26 PM
cn90 cn90 is offline
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Quote:
Originally Posted by 4thBMW View Post
This subject is all detailed in Bentley's....All four wheels on flat level surface; 150 lbs. in each ft. seats; 150 lbs in middle of back sat and full tank of fuel. That's what the book says for stock bushings for final torque down. If you are doing this work you should have the book. BMW's need to be doneby the book, unless you find a good short cut...then tell us. Good luck.
As I mentioned above, BMW TIS should be followed, however, one should keep in mind that not everything BMW says makes sense. In other words, there is more than 1 way to do things.

Doing it BMW way (option "c" above), is fine while driving but not when the car is parked.

The majority of car makers out there (Volvo, VW, Honda etc.) do not specify extra weights.
So these car makers go for Option "b".

The bottom line is: the difference in bushing actual load between "b" and "c" is negligible.
I did an angle measurement and it was virtually nothing significant (measure the fender-to-wheel distance with and without extra weights, the difference is less than 1 inch! I posted info in forum in another thread.

So either "b" and "c" is fine.
Just take your pick.


PS: The more cars you fix, the more perspectives you get from fixing different brands.

Last edited by cn90; 04-15-2012 at 12:28 PM.
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