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Suspension & Braking
Have some questions about suspension or brake setups for your E46 BMW? Get all your answers here!

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Old 09-17-2013, 11:09 PM   #1
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Exclamation So, you wanna service the rear trailing arm? Definitive Trailing Arm Guide

Definitive Trailing Arm Guide

This thread will guide you on how to properly service your rear trailing arm.

BMW has been using the rear trailing arm for decades. Its design coupled with careful suspension tuning has been one of key ingredients to BMW's dynamic driving qualities.

The BMW rear trailing arm serves for the backbone of the rear suspension/wheel/wheel bearing/brakes and is designed to provide toe-out under heavy acceleration and toe-in during heavy braking. These characteristics is to stablize the vehicle.

The rear trailing arm bushings AKA "RTAB" (as pictured in blue) helps deflect vibration and harshness while absorbing shock mid-corner which could otherwise upset the vehicle's stability.

These bushings fail quickly and often because they are high-load items and a lot of work is asked of them. Typical life expectancy is anywhere from 35,000 to 70,000 miles. The effectiveness of these parts are not an "on/off" switch and their performance degrades over time as the rubber deteriorates. You may not feel that you need new RTABs if you have slowly become used to their gradual decline in performance. Common signs of failure of the RTAB includes rear-end wandering often tmes under acceleration or braking or in more severe cases, clunking noises.

The other two components pictured are the rear trailing arm bushing and/or balljoint. These items are (as pictured in red and green). These are also serviceable items but do not wear as quickly as the rear trailing arm bushing.

Note that non-M models come with a bushing at the lower location and balljoint at the upper location.

///M3 models come with balljoints at both upper and lower locations for improved feel and control.

This dual-balljoint setup can be applied to non-M models using ///M3 parts. (Thanks to CPOSK)

Rear trailing arm bushing:





Replace these at 60,000+ miles. Personally, I recommend replacing them every 20,000 miles.

M3 Rear Trailing Arm Bushing Part number (upgrade): 33326770817 (Two per vehicle)

Comments and Concerns Addressed:

Q) When should you change your Rear Trailing Arm Bushing?

A) If they are original or you don't know. If you get rear-end wandering or the rear end is unstable during acceleration or braking.

Q) But what about polyurethane?

A) I don't recommend it. On a street-driven vehicle, this bushing should be rubber. Polyurethane is not ideal for multi-axis movement and not meant for this location. I would avoid this type of bushing here.

Q) But, Mango... what about pre-load?

A) There are documented ways to do this but I've found the easiest way is to mark the position of the rear trailing arm carrier in relation to the arm after the arm is dropped. Simply re-torque the carrier after installation of the new bushing after it is aligned with the mark you made. I found on several vehicles the trailing arm bracket lined up perfectly with a line cast into the control arm. The goal is to have zero load on the bushing at rest.

Q) What tools do I need?

A) For the RTAB, the MIS RTAB tool. For the upper and lower balljoint/bushing, you need a special press for them. These can be found on Amazon and eBay such as here.

Q) What brands do you recommend, Mango?

A) I recommend Lemforder for all three locations. Personally, I am using OEM M3 parts for all three parts.

Tips:

Some people use "limiters" which are essentially plastic shims that go on either side of the rear trailing arm bushing. These spacers limit trailing arm movement within the pocket and can extend the life of the bushing.

Limiters

Before dropping the trailing arm, disconnect the brake line from the trailing arm via a 10mm bolt. This is important.

Use a large hose clamp to compress the split bushing before pressing it into the trailing arm. Press into the trailing arm on the side of the trailing arm with a beveled edge.

Torque carrier to trailing arm bushing center bolt @ 81 ft-lbs and bushing bracket to body @ 57 ft-lbs

Trailing Arm Bushing (lower and upper)



As mentioned above, this is a rubber mount. This can be upgraded to ///M3 balljoints.

Rubber mount part number (2 per car on non-M models): 33326771828



M3 balljoint part number (2 per car on non-M models and 4 per car on M3 models): 33326775551



These are torqued to around 78 ft-lbs (99% sure) if someone can find the official spec, I'd appreciate it.

Tips:

Remove rotor and set caliper aside. Mark your camber position before removing your camber bolts.

An alignment is recommended when servicing any of the above items.
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Last edited by Mango; 10-02-2013 at 02:36 PM. Reason: Auto-save 1380742560
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Old 09-17-2013, 11:30 PM   #2
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Re: So, you wanna service the rear trailing arm? Definitive Trailing Arm Guide

Awesome write-up! Thanks!
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Old 09-18-2013, 01:43 AM   #3
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Planning on buying this tool as the MIS tool is expensive to buy in the UK after shipping http://www.ebay.co.uk/itm/BMW-3-Seri...item3f28862c28
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Old 09-18-2013, 01:43 AM   #4
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Very nice Mango. Does the car feel different after replacing the trailing arm ball joints?
Did you forget or chose not to comment on the RTAB limiters?
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Old 09-18-2013, 05:06 AM   #5
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Old 09-18-2013, 09:31 AM   #6
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Quote:
Originally Posted by Megalocnus View Post
Very nice Mango. Does the car feel different after replacing the trailing arm ball joints?
Did you forget or chose not to comment on the RTAB limiters?
Oh yeah. Limiters. Yeah I supposed I could add those. It feels slightly more direct with slightly more noise in the back. I've gotten used to it now. Basically it will feel similar to an M3 with M3 RTABs. I believe the M3 shares all other rear control arm bushings
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Old 09-18-2013, 12:33 PM   #7
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Thanks Mango. I've got the RTAB's on my list.

Quote:
"The other two components as pictured are the trailing arm balljoint and trailing arm bushing. These are also serviceable items but do not wear as quickly as the rear trailing arm bushing."
what mileage to you consider these to be completely shot? I think this is what you consider to be the Stage 3 job in your suspension write up right?
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Old 09-18-2013, 12:34 PM   #8
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Thanks Mango. I've got the RTAB's on my list.



what mileage to you consider these to be completely shot? I think this is what you consider to be the Stage 3 job in your suspension write up right?
I would say around 40,000-60,000 miles of use, they are "completely" shot for use in their intended purpose
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Old 09-18-2013, 12:46 PM   #9
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that means mine are probably shot considering I just turned 87k this morning. what are the alternatives on tools for this job? (other than paying someone else to do it). Does Harbor Freight have a cheap option? Do places rent that kit?

I've seen a variety of options for the RTAB tool, but even to buy it isn't too big a hit on the wallet. That other bushing set is a bit steep.

What other fancy tools are needed just to get to the point of using that bushing tool set?

Quote:
These require tons of labor and special tools. These are for the pickiest of picky. You'll need an E36/E46 rear axle service kit which can be found on eBay
I might be out of my league with the stage 3 suspension refresh. How compromised is the car if this one is overlooked?
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Old 09-18-2013, 05:51 PM   #10
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got this on my list

OK, great write up, thanks !! OK, do you have to remove the whole arm from the car to replace JUST the RTAB with the M3 part ??? I know I will need the special tool. thanks .....
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Old 09-18-2013, 05:52 PM   #11
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Also ...

Sorry .... what do you think of having the reinforcement plates that you weld onto the rear camber arm to strengthen them ????
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Old 09-18-2013, 06:07 PM   #12
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I've lightly glanced at DIY's for the RTAB's, you don't have to remove the whole arm from what I can tell.
http://forum.e46fanatics.com/showthread.php?t=678004
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Old 09-18-2013, 06:11 PM   #13
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Quote:
Originally Posted by Brad W View Post
that means mine are probably shot considering I just turned 87k this morning. what are the alternatives on tools for this job? (other than paying someone else to do it). Does Harbor Freight have a cheap option? Do places rent that kit?

I've seen a variety of options for the RTAB tool, but even to buy it isn't too big a hit on the wallet. That other bushing set is a bit steep.

What other fancy tools are needed just to get to the point of using that bushing tool set?



I might be out of my league with the stage 3 suspension refresh. How compromised is the car if this one is overlooked?
No good or cheap alternatives. Some people have gotten by making their own tools. I tried. Snapped the tool twice. You need solid blunt precision machined tools for this job.

Quote:
Originally Posted by doubleda View Post
OK, great write up, thanks !! OK, do you have to remove the whole arm from the car to replace JUST the RTAB with the M3 part ??? I know I will need the special tool. thanks .....
You don't need to remove the trailing arm to replace the bushing, no. As long as you use the correct tool.

Quote:
Originally Posted by doubleda View Post
Sorry .... what do you think of having the reinforcement plates that you weld onto the rear camber arm to strengthen them ????
Fine for track use. But for street use there is an increased risk as you could overload your subframe/chassis causing permanent damage from a simple curb strike. The stock arm is designed to deflect under impact.

Quote:
Originally Posted by Brad W View Post
I've lightly glanced at DIY's for the RTAB's, you don't have to remove the whole arm from what I can tell.
http://forum.e46fanatics.com/showthread.php?t=678004
Correct
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Old 09-18-2013, 09:48 PM   #14
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Re: So, you wanna service the rear trailing arm? Definitive Trailing Arm Guide

I am getting ready to do this on my sedan, thinking of going to the m3 setup, anything else i should do?

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Old 09-18-2013, 10:45 PM   #15
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Hmmm... well I'd do the double balljoint upgrade as well but that's going to require more tools.
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Old 09-18-2013, 10:51 PM   #16
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Even though people sometimes poke fun at Mango, I will say that he is a wealth of information and this writeup is a great example. Nice job
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Old 09-18-2013, 11:17 PM   #17
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Re: So, you wanna service the rear trailing arm? Definitive Trailing Arm Guide

Quote:
Originally Posted by Mango View Post
Hmmm... well I'd do the double balljoint upgrade as well but that's going to require more tools.
I want to do this so bad!!!!!
I just dont want to go through another alignment. Ive pissed all my shops off around here with how picky I am.

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Old 09-19-2013, 01:29 AM   #18
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I want to do this so bad!!!!!
I just dont want to go through another alignment. Ive pissed all my shops off around here with how picky I am.

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If your trailing arm bushing (lower) is in good condition, you can get by with the M3 balljoint upgrade without an alignment.
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Old 09-19-2013, 04:45 AM   #19
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Try to add methods for determining excessive wear and a DIY replacement procedure complete with lot's of pictures.

In it's current form, it's an incomplete piece, low on critical information with too much editorial. For example, I really don't care if you want to change yours ever 20,000 miles. I'd rather you explain the criteria for deciding when to change them out, with inspection procedures and example pictures. That information is completely missing.

Also, you might want to mention your recommendation for performing an alignment early in your post rather than sneaking it in on the last line of your post. It's a key consideration when deciding whether to tackle these tasks DIY vs. paying a shop to do it. Include web links to the very best additional DIY resources that exist.

Last edited by Solidjake; 09-19-2013 at 07:00 AM.
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Old 09-19-2013, 07:52 AM   #20
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In it's current form, it's an incomplete piece...with too much editorial.
+1. For example, what is the reason to choose the balljoint type bushing from the M3 vs the standard one?
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