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Thread: E46 Trailing Arm Pocket failure story

  1. #1
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    E46 Trailing Arm Pocket failure story

    I came across this article: http://www.foxsports.com/motor/story...ir-flip-052617

    The author reports that the cause of the accident was a rear trailing arm pocket failure. The RTAB pocket failure appears to have been somewhat common on E36 cars, hence all the RTAB pocket reinforcement kits that are out there for the E36. I see nothing addressing the RTAB pocket for the E46. Is it because this kind of failure is non-existent on the E46 or because it is not possible to reinforce this area of the vehicle?

    If this type of failure is rare/non-existent what could have caused the pocket failure in the article? Perhaps worn RTAB bushings causing excessive movement in the pocket or rust leading to the pocket area giving way?

    Scary. I would like to understand the issue more.

    Mark

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    There's a pretty good chance that trailing arm ripping out of the chassis was as a RESULT of the accident as opposed to the cause.

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    Quote Originally Posted by jakermac View Post
    There's a pretty good chance that trailing arm ripping out of the chassis was as a RESULT of the accident as opposed to the cause.
    Watch the video.

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    Since when do people make gofundme's to finance their hobbies? If you can't afford to fix your shit, don't race it.

    Hey guys, I need a new TV, who wants to chip in?!

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    Quote Originally Posted by TXBDan View Post
    Since when do people make gofundme's to finance their hobbies? If you can't afford to fix your shit, don't race it.

    Hey guys, I need a new TV, who wants to chip in?!
    LOL, I'm glad I wasn't the only one thinking that ...
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    I know the internet leads to some careless comments but some of the responses are embarrassing.

    Quote Originally Posted by jakermac View Post
    There's a pretty good chance that trailing arm ripping out of the chassis was as a RESULT of the accident as opposed to the cause.
    If you watched the video which he didn't have to post, you'd see that isn't the case. The pocket failed like it does on the E36s. In a pretty spectacular, scary way I might add.

    Anyone who knows the racer in that vid knows he's a class act and fast as hell. I happen to race against him when life doesn't get in the way and I can actually make an event. Don't get distracted with the gofund me anything. He's doing everyone a big ass public service by volunteering info that could have cost him his life.

    The whole point of the video was that investing in safety is our number 1 priority with this hobby. Skimp someplace on the car but not on safety. That's the only reason he walked away to tell the tale. A lot of drivers, pro and amateur, have lost their lives helping accelerate the safety innovations we have today.

    Hans, Halo's, Helmets, Fire suppression, proper roll cage design/install etc, etc, etc. made this walk away scenario a reality. That racer credits the technology to it but is also emphasizing to be very rigorous with chassis inspections, nut and bolt checks, cracked wheel checks etc.

    BTW, I'd offer all the spare parts I have to help someone get back on track when needed. Most everyone I know at a track event would do/has done the same for me or someone else. Asking for help after a massively expensive incident like that isn't out the question.

    Especially when you're still motivated and trying to finish out a competitive season. Yep, all of us know the risk and go in eyes wide open knowing we could leave with nothing except our shoes when an incident happens.

    It doesn't make the pain any less when it actually happens. Focus on the pain free, zero impact to your wallet lesson conveyed so we can all stay safe.
    Last edited by Maynor; 05-29-2017 at 12:16 AM. Reason: Pro/Amatuer comments
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    I dunno, there's a trend of people setting up GoFundMe's so they can do another round of modding on their car. That's unseemly and I personnally think is beyond lame.

    I'd offer up spare parts for a fellow racer but I'm not giving him money to finish a season. Asking those around you to contribute to your amateur hobby isn't right.
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    90% of the same issues with the E36 carried over to the new E46 at the time....for some reason BMW didn't learn.

    Actually that guy is smart doing a "GoFundMe" since people are stupid and will pay up (this happens on Ebay too). Apparently there are people sending money to Elvis Presley who still think he's alive.

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    The racer is someone local to my region and I've never met him personally we have overlapping friends (no surprise there as racing is a small world).

    One piece of data that is often left out of the discussion on this incident is (as far as I have been told) this chassis has been a race car for over a decade. I think people forget that chassis age-out and should be retired. I suspect that was the root cause of this failure.

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    Quote Originally Posted by Maynor View Post
    I know the internet leads to some careless comments but some of the responses are embarrassing.



    If you watched the video which he didn't have to post, you'd see that isn't the case. The pocket failed like it does on the E36s. In a pretty spectacular, scary way I might add.

    Anyone who knows the racer in that vid knows he's a class act and fast as hell. I happen to race against him when life doesn't get in the way and I can actually make an event. Don't get distracted with the gofund me anything. He's doing everyone a big ass public service by volunteering info that could have cost him his life.

    The whole point of the video was that investing in safety is our number 1 priority with this hobby. Skimp someplace on the car but not on safety. That's the only reason he walked away to tell the tale. A lot of drivers, pro and amateur, have lost their lives helping accelerate the safety innovations we have today.

    Hans, Halo's, Helmets, Fire suppression, proper roll cage design/install etc, etc, etc. made this walk away scenario a reality. That racer credits the technology to it but is also emphasizing to be very rigorous with chassis inspections, nut and bolt checks, cracked wheel checks etc.

    BTW, I'd offer all the spare parts I have to help someone get back on track when needed. Most everyone I know at a track event would do/has done the same for me or someone else. Asking for help after a massively expensive incident like that isn't out the question.

    Especially when you're still motivated and trying to finish out a competitive season. Yep, all of us know the risk and go in eyes wide open knowing we could leave with nothing except our shoes when an incident happens.

    It doesn't make the pain any less when it actually happens. Focus on the pain free, zero impact to your wallet lesson conveyed so we can all stay safe.
    I'm 100% glad he's ok and also glad he posted the video as a PSA on race car inspection and maintenance. That said, there are no heroics here that distinguish this from any other failure related crash that happens every weekend across the country. Asking others to help pay his way through an expensive and completely unnecessary hobby is selfish. How privileged must somebody be to think that their own entertainment is so important that other people should pay for it. Sorry, but this guy needs a healthy dose of reality. We're spending stupid money on a stupid hobby that benefits no one but ourselves. The least we can do is pay for it.

  11. #11
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    Thanks for posting the link, good information.

    I'll stay off the GoFundMe stuff - you're right, the pocket failure should be the focus of this thread - and the fact that he walked away is awesome.

    Not trying to get on anyone here - just saying thanks for posting. I recently had body damage on my car but it was much lower speed and no lives were in danger - so it's a little raw for me.
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    The driver is a good friend of mine and I was about 10 cars back in that qualifying session where the failure occurred. And I helped rip the car apart yesterday so the chassis can be scrapped.

    The first data point to add in is that this car was sold new as a Body In White to TCKline as a (very built) 325i/M54 car. It's been a racecar since day one, and had an annual tech sticker from the year 2000 on the cage. 17 years of racing, bumping things, jumping curbs, probably being crashed a few times before his ownership, etc will definitely weaken a chassis.

    As we pulled it apart, it was interesting to see what and how other things were reinforced. The cage was very, very well built and tied into the shock towers, with nice welds and gusseting. It speaks volumes of the cage builder that this car rolled its way down to Oak Tree (watch the video, it got airborne at roughly 93 mph) and that the driver was able to give me and the other drivers a big thumbs-up as we crept past the incident under full-course yellow, then walk himself into the ambulance and be otherwise fine.

    Second point: safety safety safety. Don't cheap out. Do it right.

    I know I and many others appreciate him being so public about this crash and the failure point. It's not something that's been seen on the E46 chassis much/at all but important for others to know about and check/reinforce. As for the GoFundMe, I don't necessarily see it as him asking other racers to fund his car, but rather a central point for family/friends who may buy a birthday gift or something similar to see that this would be the preferred "gift idea" of 2017 instead of a new blender or whatever. If you've met him, he's a fast driver and class act in the paddock. Always willing to help others out and give away parts in his trailer if it will help you finish your weekend.
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    Quote Originally Posted by dmw16 View Post
    The racer is someone local to my region and I've never met him personally we have overlapping friends (no surprise there as racing is a small world).

    One piece of data that is often left out of the discussion on this incident is (as far as I have been told) this chassis has been a race car for over a decade. I think people forget that chassis age-out and should be retired. I suspect that was the root cause of this failure.
    Plenty of 20+ year old cars out there ... even much older than that. If properly built and inspected, and disassembled every couple years for refresh there is no reason to retire a good race car. Our 1999 DTC motorsport chassis e46 is surely not going to be retired anytime soon because it's getting on 17 years of racing. But it surely is take apart to bare chassis and cleaned up and inspected.
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    Is it common practice to pick up the subframe mounting points on E36 / E46 chassis with the cage?

    I ask because I don't know.

    We do it on E30s because thats what the factory did in the Gruppe A cars, but not sure if that practice carried forward to the E36 & E46 chassis.
    I seem to see lots of club / DE E36-46 cars with just rear bars to the rear wheel wells or sometimes triangulated to the shock towers.

    If not triangulated to the rear subframe points, possible correlation to failures (which it seems we hear a lot about rear subframe tearing on E36s)
    Last edited by jimmypet; 05-30-2017 at 02:55 PM.
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    Quote Originally Posted by jimmypet View Post
    Is it common practice to pick up the subframe mounting points on E36 / E46 chassis with the cage?

    I ask because I don't know.

    We do it on E30s because thats what the factory did in the Gruppe A cars, but not sure if that practice carried forward to the E36 & E46 chassis.
    I seem to see lots of club / DE E36-46 cars with just rear bars to the rear wheel wells or sometimes triangulated to the shock towers.

    If not triangulated to the rear subframe points, possible correlation to failures (which it seems we hear a lot about rear subframe tearing on E36s)
    Yes, most well built e36 and e46 cages, if the rules allow, will have the cage tied into the rear subframe. Doesn't help the RTABs though, never seen those tied in.
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    Quote Originally Posted by ScotcH View Post
    Yes, most well built e36 and e46 cages, if the rules allow, will have the cage tied into the rear subframe. Doesn't help the RTABs though, never seen those tied in.
    So what failed on the video car was not somewhere that could be tied into the cage?
    Again asking,,, because I don't know.

    I assumed it was a situation that a subframe attach ripped out of the chassis.
    Is that not what happened here?
    jimmy p.


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    Quote Originally Posted by jimmypet View Post
    So what failed on the video car was not somewhere that could be tied into the cage?
    Again asking,,, because I don't know.

    I assumed it was a situation that a subframe attach ripped out of the chassis.
    Is that not what happened here?
    Correct, that is not what failed.

    The failure was the entire "cup" that the rear trailing arm bolts to. It is not a part of the subframe assembly - you must unbolt the two trailing arms from these locations before you can take the whole subframe down from the rear of the car. The cup appears to be spot welded to the chassis from BMW, and those spot welds failed, allowing the trailing arm to rip out of the chassis while still "bolted in" where it belonged.
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    Quite interesting. FYI, RealOem shows the RTA cup exactly the same for the E36 and E46. The failure mode on the E36 is the 3 bungs for the cup bolts are welded to the car insufficiently, and welded to chassis metal that's insufficient (for the stresses of the track).

    Here's the chassis of my E36 cleaned up prior to welding RTA reinforcements. The cup bolts into this pocket to the 3 bungs.

    Last edited by aeronaut; 05-31-2017 at 01:26 AM.

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    Jake -- You were there for the tear down. I am assuming that the failed spot welds are not visible from underneath the car even with the trailing arm removed, right?

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    Quote Originally Posted by OCRentAPopo View Post
    Jake -- You were there for the tear down. I am assuming that the failed spot welds are not visible from underneath the car even with the trailing arm removed, right?
    I honestly didn't even look. We were there from 10 AM to 6 PM just stripping every last thing off of the car and I didn't work on the rear subframe area at all. He does still have the shell, so it'd be worth asking before he disposes of it.
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    Sorry to bring back this thread but I'm looking for more info on RTAB reinforcement specifically for the e46 chassis and this thread is more recent than the other one I found from 2010 here: https://www.bimmerforums.com/forum/s...Bucket-Warning

    In the aforementioned thread the seemingly very seasoned e46 driver "CP Louie" says the e46 only needs the edge welded, thus no reinforcement plate necessary, can anyone else back this up? To my knowledge there is currently only one kit made for the e46 (VAC) while all others are for the e36, and I'm not sure how long VAC's has even been out as it seemed in May 2017 member "markn91387" stated above there was not a kit available.

    I'm relatively new to the e46 platform as i acquired mine in May 2017, thanks for any input and advice!

  22. #22
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    We've tracked and beaten the crap out of our e46s for years. No issues. The BMW Motorsport chassis only has them welded around the bung. Our in-house build was the same. Neither ever had any issues.
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  23. #23
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    I have welded up a bunch of e36 rtabs. You connect the plate to the threaded bosses and then plate to the chassi. The failure with the e36 is the threaded bosses crack at the welds and break free from the pocket. The failure on all of the e46s that I have seen on the internet is the whole pocket breaks loose from the chassi. The small spot welds are what fail, stitch welding the pocket along the perimeter is all that is needed in my opinion. I looked really close at that area on the last sub frame job i did. Adding a plate in there doesn't help spread the load out much wider then whats already there compared to the e36.

  24. #24
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    Quote Originally Posted by eye145 View Post
    I have welded up a bunch of e36 rtabs. You connect the plate to the threaded bosses and then plate to the chassi. The failure with the e36 is the threaded bosses crack at the welds and break free from the pocket. The failure on all of the e46s that I have seen on the internet is the whole pocket breaks loose from the chassi. The small spot welds are what fail, stitch welding the pocket along the perimeter is all that is needed in my opinion. I looked really close at that area on the last sub frame job i did. Adding a plate in there doesn't help spread the load out much wider then whats already there compared to the e36.
    Oh yeah ... forgot about also welding around the pocket itself
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