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General E46 Forum
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Old 06-29-2009, 01:03 PM   #1
akita328
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How safe is the car after repaired subframe?

I've been reading up a lot on the E46 subframe cracking and repairing/reinforcing on the web, especially after I got a letter on the class action suit (that's how I found out.. argh. how ignorance is bliss..). And found many scary-looking videos, photos, and repair process on the web and learned a lot. I also looked for any discussion on how safe the car is *after* the repair has been made on a cracked subframe, but couldn't find any. All the topic is to replace or reinforce (as a preventative measure or to fix very bad failures), but none on the condition of the car after the repair has been made.

I'm no mechanic, but a materials engineer, and to me, a fatigued metal that has cracked once spells danger of future failures. One can always find micro-fractures that is not visible to the eye, that can develop or has developed after the repair and fail in the future. and usually after a crash, a "cracked frame" usually prompts people to sell their car after repair, due to safety implications... I understand subframe isn't exactly as vital as the frame itself, but how safe is the car with a faulty subframe that was fixed by welding cracks together or putting new plates on? I just don't know enough about cars and how they are put together to get a sense of what type of failure this is, and whether how detrimental it is to the change in the overall reliability of the car for long term (I intend to keep this car for a very long time)

So I was wondering, after repairing subframes (just cracks or ones that has totally separated), what are your thoughts on how safe the car is to drive long term after the repair has been made. Do we still have to keep looking at it so that new cracks don't appear? Or after once the repair is made, it's considered "good as new" and can go my merry way?

I was hoping to get the opinions of what people on this forum think of how stable the repaired subframe is for the car...

Linda
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..and I think I have a cracked subframe.. will have to get it checked...
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Old 06-30-2009, 10:30 PM   #2
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Old 06-30-2009, 10:34 PM   #3
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It better be or else they're gonna have one hell of a lawsuit on their hands...again...
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Old 06-30-2009, 10:59 PM   #4
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i hope it will be fine
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Old 06-30-2009, 11:07 PM   #5
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Its just as safe after it's been fixed. Had mine fixed two years ago and it's still solid as a rock today.
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Old 06-30-2009, 11:39 PM   #6
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I think as engineers, we tend to over-analyze. Sure what's a few more sleepless nights...but you have a brought up a good pt. If we repair/strength certain section of the frame, will there be other weaker links? The force has to travel to the weakest link and stress out that link. Unfortunately, until we have the actual CAD files and perform a full blown FEA subjected to theoretical road disturbances, we may never know. But one thing is for sure: look to what E46 racers have experienced on the track. Cos what they do on the track is essentially an "accelerated" wear and tear program for street/daily drivers. Case in pt: Turner Motorsports. If you see they have an reinforcement kit, then yes, they did that for their E46 race chassis.

The key here to this subframe issue, IMO, is how it is being repaired. Yes we have heard so much as "a repaired piece will never be like before". But I believe under a watchful and experienced welder, a damaged subframe can be repaired and reinforced to take on further road harshness. Which is why I am very hesitant to bring the car in and perhaps have one of their techs work on the subframe. Because

1. BMW techs aren't trained to be welders.
2. I doubt BMW NA will pay them to go through a welding course. Even if they do, they have no previous experiences.
3. I just don't trust dealers.
4. BMW NA is just doing to get us off their back.

If any, I have already secured an appt with a welder who has race experiences and has worked on race cars.

If I were you, I'd find a well known welder in your area. Get it done once and get it done right. That is of course if you do indeed to keep the E46 around for a long time.
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Old 07-01-2009, 07:54 AM   #7
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I received my class action proposed settlement letter a couple days ago also. I didn't read it thoroughly because I was already aware of this issue and recently inspected my car for this damage and didn't find any. IIRC, however, the letter said that BMW would reimburse customers for any out of pocket expense already incurred due to subframe failure OR be able to bring it to a dealer for inspection/repair.

So read the proposal again, but I don't think you have to bring it to a dealer if you have another place that you think would do a better job.
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Old 07-01-2009, 08:23 AM   #8
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If the crack is longer that 25mm (iirc) BMW replace the boot floor.. At least, thats what i was told and thats what they did with mine.... actually, forward front half of boot floor, and its a new panel, spot welded ( i assume) in place. I would not have been happy with just having the crack welded up tbh.
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Old 07-01-2009, 08:31 AM   #9
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don't you have to sign onto that class action lawsuit to get the repair covered?
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Old 07-01-2009, 08:32 AM   #10
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If you're a materials engineer then I wouldn't think you'd need our opinions
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Old 07-01-2009, 09:08 AM   #11
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The cracking and failure happens to the driverside first. There are rare instances that it happens on both sides but even mine just the driverside(read about why) if you re-inforce the driverside only you will be fine. I put my plates in around 100k miles due to creaking noises. The passenger side was fine and there were no signs of creaking and andything negative for an extra 60k miles.
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Old 07-01-2009, 09:58 AM   #12
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Safer than before it's repaired

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Old 07-01-2009, 10:48 AM   #13
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I had both rear driver and front passenger mounts torn out , welded both in myself (drilling a couple of holes and just filling them up).

It's the WELDS that gives , not the material in itself , once the welds give the mount drop down on the chassis which then "tears".

Welding up the taers and securing the mount better than the first time is in my opinion stronger than the OEM construction.

I welded the mounts all the way around to really secure then , then i welded a steel plate about inch thick on top of the welds and drilled some holes down to the mount and then filled it again.

And to add further protection i installed the TMS reinforcement plates
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Old 07-01-2009, 02:36 PM   #14
akita328
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Originally Posted by phrozen06 View Post
If you're a materials engineer then I wouldn't think you'd need our opinions
well, materials engineer part will say get the part replaced, not repaired.. but then there are always other mechanical engineering considerations that I have no clue (how integral this sub frame is to structural integrity, weakness is only at the mount point and nowhere else, etc) that having other minor stress cracks will have no consequence... and stuff like that, I'd figured the E46Fanatics folks would have a better sense.

if done correctly, the weld should be stronger than the original material... so then the question is, the weld might hold, but what about the surrounding area?

replacing the sub frame if the crack is greater than 25mm sounds like a good thing... although many of the photos I've seen looks as if the cracks/tears are far larger than 25mm!

as for paying third party repairs, I'm not sure if BMW will pay if we go and get it repaired after the settlement... (only if done prior to the settlement, and since the issue isn't "settled" yet, it's a risk to go elsewhere and assume BMW will pay). It's not clear on the law suit claim on that regard. Some of the quotes i've read on the web has been anywhere from $500 to $4500 (few people reporting the high-end quote has opted to get rid of the car...). Number of people have said that the BMW dealer has referred them to a body shop for repair. One would assume they would refer to a reputable body shop, but...
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Old 07-02-2009, 01:37 AM   #15
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Originally Posted by Mr Paddle.Shift View Post
1. BMW techs aren't trained to be welders.
2. I doubt BMW NA will pay them to go through a welding course. Even if they do, they have no previous experiences.
3. I just don't trust dealers.
4. BMW NA is just doing to get us off their back.
BMW techs are not the ones who perform subframe repairs. BMW sources out the repair job to a BMW approved body shop with professional welders.
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Old 07-02-2009, 11:54 AM   #16
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Originally Posted by MachRc View Post
The cracking and failure happens to the driverside first. There are rare instances that it happens on both sides but even mine just the driverside(read about why) if you re-inforce the driverside only you will be fine. I put my plates in around 100k miles due to creaking noises. The passenger side was fine and there were no signs of creaking and andything negative for an extra 60k miles.
.
You said creaking noises...I am experiencing some as well maybe some people could shed some light on whether its the frame or not...

I live in a house and when I pull out of the driveway and go over the curb, i tend to start to turn the wheel to back out so one rear wheel will dip down from the elevated curb onto the street first and then the other side. so for that one second where the two wheel are at an angle and not horizontal, it creaks. Then when it levels out, no creaking noise.

Also the same thing happens when I am parked and put the gear into reverse or drive. When I hold my brake with a lot of force...no squeak. If I'm not pressing with all my might, it squeaks everytime I put it in gear or go over a bumop
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Old 07-02-2009, 12:26 PM   #17
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its quite easy to get over the anxious murderous do-I-have-a-subframe-damage thoughts for the average guy in the garage. Just jack up the car by the rear jackpoint on the driver side..slip in a old rim under the driverside for safety when using the factory jack..please..just in case, throws some tires or something.. really quickly make yourself under the car from the left side behind the rear driverside wheel of the exhuast and look for the circualr piece as shown in the picture you'll find it..



and use a flashlight to check the surrounding..very easy..




and no more fear of subframe, just crappy steptronics.
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Old 07-02-2009, 12:39 PM   #18
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It should be safer than leaving the rips.
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Old 07-02-2009, 12:53 PM   #19
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You said creaking noises...I am experiencing some as well maybe some people could shed some light on whether its the frame or not...

I live in a house and when I pull out of the driveway and go over the curb, i tend to start to turn the wheel to back out so one rear wheel will dip down from the elevated curb onto the street first and then the other side. so for that one second where the two wheel are at an angle and not horizontal, it creaks. Then when it levels out, no creaking noise.

Also the same thing happens when I am parked and put the gear into reverse or drive. When I hold my brake with a lot of force...no squeak. If I'm not pressing with all my might, it squeaks everytime I put it in gear or go over a bumop
anyone got any ideas about my squeaking noises? is this a subframe issue?
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Old 07-02-2009, 12:55 PM   #20
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Just go check!^ what is asking here going to do? take 10 minutes of your life..
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