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2001 E46 330i RTAB question

2K views 8 replies 5 participants last post by  Paddy2bsure 
#1 ·
Having replaced literally everything there is to replace on the front suspension & steering, I'm finally happy with the way the car drives! But... striving for perfection, I'm going to tackle the Rear Trailing Arm Bushes (RTAB's) soon as they're still 2000-vintage. I've been doing some research...

I can powerflex them, but seemingly these will then only allow rotation of the Trailing Arm about the bush, and cannot pivot vertically to allow for suspension movement, which may cause premature wear of other suspension components. This site is worth a read!

I could put a like for like bush in there, and it would probably last another 128,000 miles like the original ones have!

Or I could follow the Vorschlag recommendadtion of putting OEM M3/Z4M ones in there which are more durable/stiff than the standard ones, but more flexible than the Powerflex ones in allowing some pivoting to accomodate the rest of the suspension movement.

Installation-wise, they're much of a muchness, as the new BMW bushes are split to allow compression for installation (see this month's Car Mechanics for one they did on an E36 Compact).

Any comments welcome :thumbsup
 
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#2 ·
I don't really understand what they are talking about in their explanation about the bush binding. Do they mean the bush will bind as the trailing arm pivots up and down with the suspension? The Powerflex bushes i fitted to my car can rotate freely on the inner bush so there is no binding as the arm moves up and down, unlike the standard bush where the rubber is bonded to the inner bush.
If they are talking about lateral movement then i have to ask why they are fitting spacers to limit this?
I'd be very interested to learn more about this if any suspension techs can explain this for the hard of thinking (me!).

Jim.
 
#3 ·
Good find Paddy - there's food for thought!

I understand some poly bushes are bonded to the steel and would cause this 'bind' in the vertical pivoting of the suspension, however I don't think powerflex bond their bushes so would not suffer from binding??
But would prefer to use OEM if possible, especially if its an 'improoved' solution.
 
#4 ·
Read a similar post on another forum and my E46 M3 driving mate also read like info on his M forum, our conclusion was to machine limiting kits from aluminium and fit them when the OEM RTAB's were replaced.

Mine have been in now for a month and I can't tell any difference, though having a 4 pot sludger and putting the rear suspension under that much pressure seldom go hand in hand.

My mate with the M3 is having OEM RTAB's & limiting kit fitted this week so I'll ask him if he feels the limiting kit offers any significant improvement :thumbsup
 
#5 ·
Thanks for the comments above guys.

The thing about the pivoting action (as I understand it) is that the trailing arm, when fitted with the Powerflex bushes, can literally only rotate around the bush. The angle of it can't change vertically even though the rear suspension does change angle vertically (picture the car with no load, then fully loaded). The normal flexible OEM bush can accommodate those changes, but the powerflex one, as it's so stiff, can't.

I can see the attraction of the nylon cups either side of the OEM bush - you get factory ride comfort, but the bush movement is limited to control geometry better.

At the moment I'm leaning towards the M3/Z4M bushes, they're £40 the pair, and will undoubtedly last the remainder of my cars life. Hopefully!
 
#6 ·
Mate I'm doing mine ATM and it took the piss right outa me! Just cudnt loosen the bolts at all finally got the 3 holding the rear trailing arm onto the car (after actually snapping a draper extension bar) then got angry and rounded a bolt of so hammerd a 11/16th on and finally got it then fought with the other two after alot of wd40 finally got it so then tried undoing my brake hose to no avail and tried to get the bush of the arm and couldent becouse the bush makes it really hard! Nightmare! (but I was doing all this in the pitch black with a head torch!) so good luck :p I just hope I can get the bush out tonight!!!!!
 
#9 ·
I know the E36 M3 & E36 M3 Evo differ (the latter having the same part number as the E46 M3 & Z4M), but I also know that BMW have upgraded these bushes to the newer split type bush, and (I believe) made them more hard-wearing too.

Hmmm...
 
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