Thrust arm bush another BMW poor design?

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07-24-2005, 11:59 AM
Gene in NC

Thrust arm bush another BMW poor design?

Seems to me that thrust arm bush is another BMW design failure. Why should the rubber be in shear from the up/down motion of the front suspension. Rubber doesn't tolerate that load well. Well advised to tighten bolt with full chasis load. Clever diversion.

Isn't the thrust there primarily to absorb braking loads? At least is is properly named, or renamed. There are springs and shocks to absorb and control the up/down loads.

Why can't we have a urethane or whatever bush with a zerk to solve the shredded bush problem? Do I recall that someone was selling same for e30?

On the other hand, maybe the old adage applies. If a masochist desires punishment, only a sadist would say no. BMW loyalists can continue the BMW has no warts, see no evil approach but I get d tired of perpetuating their apparent design failures.
07-24-2005, 12:07 PM
brodee

It is a poor design. These cars have a few areas like that. But I can tell you from all the cars I've owned (somewhere around 20) these cars have far less of these design issues than others out there. There is no perfect car, but from what I've driven these come pretty damn close.

Deal with a few bad issues or get a different car if it bothers you so much. For me I will replace the bushings every now and then and go away smiling.
07-24-2005, 12:38 PM
TheDuke

I've just got some new 740 bushings with new thrust arms yestarday. Arms are aftermarket. I only wonder how long will they hold....
07-24-2005, 12:41 PM
Jon K

i did the whole 750 bushing thing with new arms + lower control arms + new arms... over $400 in parts... $50 of it was tie rod ends... and then about 2 months thereafter my shimmy was back. So, rather than screw around with rubber/filled bushings, i went with Grunt poly urethane bushings. www.gruntsbushings.com fixed my shimmy completely. so far so good.
07-24-2005, 02:52 PM
Bill R.

I work on a large number of different cars and I would have to

say that typically most of the bmw's that I change the thrust arms on have in excess of 100k miles on them at the time... I hardly consider this a design fault to last this long...The only ones i am seeing early failures in are cars that have either had them installed incorrectly, or used cheesey aftermarket parts or have other modifications that are increasing the load on the bushings. Such as large wheels/tires/ shorter stiffer springs etc that don't allow the other components to absorb as much of the normal punishment and transmit more of it to the bushings...
The failure rate i see is just about the same as i see on mercedes thrust arms and volvo as well. http://www.bimmernut.com/%7Ebillr/im...ted%20copy.jpg

Quote:

Originally Posted by Gene in NC

Seems to me that thrust arm bush is another BMW design failure. Why should the rubber be in shear from the up/down motion of the front suspension. Rubber doesn't tolerate that load well. Well advised to tighten bolt with full chasis load. Clever diversion.

Isn't the thrust there primarily to absorb braking loads? At least is is properly named, or renamed. There are springs and shocks to absorb and control the up/down loads.

Why can't we have a urethane or whatever bush with a zerk to solve the shredded bush problem? Do I recall that someone was selling same for e30?

On the other hand, maybe the old adage applies. If a masochist desires punishment, only a sadist would say no. BMW loyalists can continue the BMW has no warts, see no evil approach but I get d tired of perpetuating their apparent design failures.
07-24-2005, 03:02 PM
shogun

Bravo, Bill!
that is exactly the point.
I do not have any problem with that.
07-24-2005, 03:15 PM
Derek A.

The only poor design element is not being able to service the ball joint independently of the arm. Nothing bad ever really happens to the metal its the ball joint or thebushing that goes south.
07-24-2005, 05:20 PM
Mobius

Quote:

Originally Posted by Bill R.

The failure rate i see is just about the same as i see on mercedes thrust arms and volvo as well.

Seriously. Thrust arm bushes last in excess of 50,000mi when installed correctly - sometimes more than 70,000mi. This is hardly a design flaw, it's perfectly acceptable wear for a rubber suspension part on any car.

If the OP thinks the TA bushing is bad - may he never have the horror of experiencing the downright insane suspension setups on older Mercedes and such. Having only two bushings per wheel in a front suspension that functions as well as it does is design genius.
07-25-2005, 07:44 AM
Gene in NC

100,000 mile life doesn't sound too bad, but Grandma's '89 525 got 60k on the original factory thrust bush and 81k on the 750s. My '94 Chev Sub at 199,475k that has done some real work has all original FE and is still tight. Of course, the Chev has zerks.

Ah, but the zerks are not sophisticated or modern.
07-25-2005, 07:59 AM
Gene in NC

e30 control arm bush from Bavarian Autosport is greasable via hole in the bush that is capped by a screw. Why wouldn't that work on e34?
07-25-2005, 08:05 AM
Gene in NC

Front end shake on BMW is not a new problem. In '69 my '68 2002 had shake from 52 t0 67mph. Trailing control arm had a big fat soft rubber bush at the front attach to frame point. Shimmed it to hard with a stack of non metric washers. No shake and better turn in.
07-25-2005, 02:39 PM
winfred

e38s and e39s do it too it's just a harder to replace and more expensive bushing, you want crap the rear suspension ball joints on the e38/9 suck
07-25-2005, 02:54 PM
Jose

Same goes for the X5, rear bushings die after 100 K.
07-25-2005, 03:02 PM
winfred

id suspect their about the same as the e39 the x5 is based on, that big through bolted ball joint on the bottom and that wimpy upper link with it's ball joint

Quote:

Originally Posted by Jose

Same goes for the X5, rear bushings die after 100 K.
07-25-2005, 04:21 PM
pundit

Don't worry about the thrust arms, what about the E34's clunky wiper mechanism.