Page 1 of 3 123 LastLast
Results 1 to 10 of 22

Thread: How concerned should I be about subframe/floorpan cracks and autocrossing?

  1. #1
    Join Date
    Jul 2016
    Location
    Enterprise, Alabama
    Posts
    18

    How concerned should I be about subframe/floorpan cracks and autocrossing?

    I used to autocross a lot growing up. I started out in a 71 Triumph Spitfire and moved up to Formula Fords, then Formula 440, and various street cars. I would really like to get back into it as we have an excellent place to run (has been held in the same place for over 40 years). I have a Convertible ZHP, unfortunately with the 5sp auto and I have been reading up on the weaknesses of the E46 and cracking. I am not looking to get terribly serious, but I will run another set of wheels and tires, and I am upgrading the brakes to stop techs and that will be pretty much it for now. My ZHP sits low enough already as I drag the bottom more than I should so I won't be lowering it.

    With all this being said, if I run her once a month or less frequently, do I need to be alarmed about the structural integrity of my E46? If I get real serious again, I may just buy and E30 or an E36 and gut it to build a autocross/track car.

    Thanks!

    2013 Camaro 2SS The Wife's!
    2015 Silverado RS The Family Truckster!
    2002 Lancer ES The Back-up Plan!
    2006 330CIc ZHP My Daily Driver!

  2. #2
    Join Date
    Jan 1970
    Location
    Branford, CT
    Posts
    15,570
    Don't worry about it.

    Sent from my LG V10 on Tapatalk
    BP
    2005 330i ZHP / 6MT
    Imolarot / Naturbraun



    It's not the car you drive, it's how you drive it.

  3. #3
    Join Date
    Jul 2016
    Location
    Enterprise, Alabama
    Posts
    18
    That's kinda what I was thinking, but I was still a bit concerned as this car means more to me than any other I have!

    Mostly I have seen the issue with M3 cars and ones that have not been properly set up for track!

    Thanks again!

    2013 Camaro 2SS The Wife's!
    2015 Silverado RS The Family Truckster!
    2002 Lancer ES The Back-up Plan!
    2006 330CIc ZHP My Daily Driver!

  4. #4
    Join Date
    Feb 2016
    Location
    Portland, Maine, USA area
    Posts
    833
    In recent month's I've run this question past the three BMW-centric shops I trust most near me. I have some mods, as listed in my sig here. Every one said not to be worried. One guy said he'd seen thousands of E36/46 cars including many racers come through the shop and not one had experienced subframe damage.

    With luck, you'll hear from the other side here. I know there are owners here who got bit by subframe failure and can tell you about their experiences and opinions.
    2006 6MT Coupe, Alpine White Premium, Cold Weather and Xenon packages
    MFactory 3.38 LSD 27mm M3 bar ECS strut brace Koni FSD's


    Other tweaks: see my profile




  5. #5
    Join Date
    Jan 2016
    Location
    Helena, AL
    Posts
    633
    Sometime in 2004 BMW started changing the rear subframe reinforcement by using some structural foam/epoxy inside the rear of our E46s in response to the TSB they issued for the rear subframe failures. With yours being an 06 and an automatic (manual tranny cars are much harder on the rear diff), with the additional floor structure from it being a convertible plus the improved foam reinforced subframe you should be fine.

    Some interesting reading here:

    http://www.zhpmafia.com/forums/showt...tion-technical

    Frank W.

    Present
    2003 BMW 530iA Saphirschwarz Metallic

    Past
    2006 BMW 330ci ZHP 6MT Silbergrau Metallic
    2014 BMW X1 xDrive35i ///M-Sport Mineralgrau Metallic
    2011 BMW 328i 6MT ///M-Sport Alpenweiss
    1999 BMW ///M Roadster Estorilblau Metallic


    plus an assortment of VW, Honda, Mazda, Chevrolet, Nissan, Toyota, and others over the years


  6. #6
    Join Date
    Jun 2012
    Location
    Socal
    Posts
    1,040
    It should be fine since auto-x is like low speed. but I would honestly just reinforce it if i were planning to keep the car forever (which it sounds like you are). i'd at least get the front reinforcement plates cause they are cheap.

    The issue is widespread on all e46 models. It's just more documented with m3s cause they actually have the money to attempt the repair lol Also they tend to push their car around harder to make the failure noticeable. Then we have all these ZHP guys that think their subframe is bulletproof because it's a later model car. If it didn't cost so much to actually check (proper check requires removal of the subframe and taking the sealant off to look at the subframe mounts), there would be way more reports. A lot of people probably have cracks, it's just not so bad that you can hear the clunk yet.

  7. #7
    Join Date
    Feb 2016
    Location
    Portland, Maine, USA area
    Posts
    833
    Quote Originally Posted by fw_fw View Post
    Sometime in 2004 BMW started changing the rear subframe reinforcement by using some structural foam/epoxy inside the rear of our E46s...
    I didn't know that. Very good news. I've found a lot of reasons to be happy to own an '06!

  8. #8
    Join Date
    Jul 2016
    Location
    Enterprise, Alabama
    Posts
    18
    Thanks for all the responses to my question and concerns. Like I said, I just want to go out and play a little bit. If I get real serious again I will buy something more purpose built. The car I have was my dad's and was his pride and joy before he passed away back in June. Riding in this car gives me lots of good memories of the time we spent together so that is why this one means more to me than my other toys!

    2013 Camaro 2SS The Wife's!
    2015 Silverado RS The Family Truckster!
    2002 Lancer ES The Back-up Plan!
    2006 330CIc ZHP My Daily Driver!

  9. #9
    Join Date
    Feb 2014
    Location
    Picton, ON
    Posts
    6,025
    lots of info at the bottom. please read (everyone).


    Quote Originally Posted by az3579 View Post
    Don't worry about it.
    why?


    Quote Originally Posted by Dual View Post
    In recent month's I've run this question past the three BMW-centric shops I trust most near me. I have some mods, as listed in my sig here. Every one said not to be worried. One guy said he'd seen thousands of E36/46 cars including many racers come through the shop and not one had experienced subframe damage.
    the issue is not with the subframe, but with the rear floor cavity. the subframe is where the suspension and diff mount to, and that in turn is mounted to the rear floor of the car. the problem lies in the rear floor cavity. more detail below.

    and, i have to assume out of thousands of E46s, that one guy was not inspecting them thoroughly enough.


    Quote Originally Posted by fw_fw View Post
    Sometime in 2004 BMW started changing the rear subframe reinforcement by using some structural foam/epoxy inside the rear of our E46s in response to the TSB they issued for the rear subframe failures. With yours being an 06 and an automatic (manual tranny cars are much harder on the rear diff), with the additional floor structure from it being a convertible plus the improved foam reinforced subframe you should be fine.

    Some interesting reading here:

    http://www.zhpmafia.com/forums/showt...tion-technical
    to be clear, starting in 10/04 (although rob's car is 9/04 and his has it, so perhaps it was late september?), BMW started putting a plastic 'filler' piece in the rear floor cavity (which is what is described in that link you posted). it is not structural foam, which is what they prescribed for earlier cars.

    the convertible RACP (Rear Axle Carrier Panel), is, i believe, the same as the coupe/sedan/touring, and is susceptible to damage.


    Quote Originally Posted by sillieidiot View Post
    It should be fine since auto-x is like low speed. but I would honestly just reinforce it if i were planning to keep the car forever (which it sounds like you are). i'd at least get the front reinforcement plates cause they are cheap.

    The issue is widespread on all e46 models. It's just more documented with m3s cause they actually have the money to attempt the repair lol Also they tend to push their car around harder to make the failure noticeable. Then we have all these ZHP guys that think their subframe is bulletproof because it's a later model car. If it didn't cost so much to actually check (proper check requires removal of the subframe and taking the sealant off to look at the subframe mounts), there would be way more reports. A lot of people probably have cracks, it's just not so bad that you can hear the clunk yet.
    to the 'low speed' comment - it's not about speed. it's about torque being applied to the RACP. you could drive the car smoothly up to max speed and drive there all day without damaging the RACP.

    you are correct about the rest. i'm sure lots more people have cracks/separation than we've heard about.


    Quote Originally Posted by toddztoyz View Post
    Thanks for all the responses to my question and concerns. Like I said, I just want to go out and play a little bit. If I get real serious again I will buy something more purpose built. The car I have was my dad's and was his pride and joy before he passed away back in June. Riding in this car gives me lots of good memories of the time we spent together so that is why this one means more to me than my other toys!
    you've got an '06, so yours has the factory RACP filler piece. does this make it immune? in my opinion, no, it does not. however it does help.

    the main issues are as follows:

    1. the RACP (Rear Axle Carrier Panel, aka the rear floor of the car) is too weak - the sheet metal is only 0.75mm thick
    2. the subframe mounting points on the RACP are too narrow
    3. the subframe mounting points need to be tied into the rear frame rails


    the early (pre-2000) E46s tore the RACP at the rear left and front right subframe mounting points. post-2000 cars got an updated RACP design (more spot welds), which was stronger, but not strong enough. post 10/04 cars got the plastic filler piece in the RACP, which definitely helps with preventing twisting of the RACP. the RACP can still crack, at the kink in the RACP just inboard of the left rear mount. this is the most common place on the post-2000 E46s. after that, the RACP separates from the chassis in the left rear wheel well.

    how do you fix this 'for good'? in my opinion, 'plates' are not a stand-alone solution. they are a band-aid for the lowest layer of sheet metal only. the spot welds will still pop, and the RACP will still separate from the chassis. you really need to tie the subframe mounting points into the frame rails.

    we are really fortunate to have a solution on the horizon - vince in sweden (on m3forum), an ME, has designed and tested his 'VinceBar' which ties the rear subframe mounting points into the frame rails, and ties the front mounting points of the rear subframe more stoutly into the RACP - in fact all 4 mounting points have a bolt-through design. to me, with this approach, the load path for the subframe twisting goes into the frame rails, not on the RACP alone; this solution makes sense. it also installs totally stealth and does not impact usability of the trunk - and for those of us wanting to keep the car forever, it will provide peace of mind.

    my car is a 6/04 build car, and i did a thorough inspection last november when i had the entire rear end out for a refresh - no cracks. however, i heard some light creaking upon take off in 1st gear last month, which turned out to be a crack developing in the RACP in the typical first-crack spot. i don't have any separation in the left rear wheel well. my 'VinceBar' (and hopefully 'VincePlates' - they are in development) will be en route from sweden in a couple of weeks. he offers a weld-in kit, and an epoxy and rivet-on kit - which is what i'm doing. i'm going to be doing a separate thread from my build thread on this process.

    so, is your car immune? no, but you at least have the factory RACP filler piece. should you keep driving it? yes! should you do regular inspections in the two common areas? absolutely - everyone should.

    peter

    2009 BMW 335i M Sport 6MT

    2015 VW Golf TSI Comfortline 5MT

    2007 BMW X3 3.0si M Sport 6MT

  10. #10
    TIRERACK.com - Revolutionizing Tire Buying
    Vince bar group buy -
    Group buy VinceBar ("subframe" fix) - laser cut components

    https://r.tapatalk.com/shareLink?url...2&share_type=t


    Sent from my iPhone using Tapatalk


    2006 Coupe | Black Sapphire Metallic | Natural Brown | Gruppe M Intake | Corsa TSE3 | Michelin PSS on Apex ARC-8 | Koni Yellows |

Page 1 of 3 123 LastLast

Similar Threads

  1. Replies: 7
    Last Post: 02-12-2016, 12:56 PM
  2. Autocrossing a Steptronic
    By Benno in forum Track and AutoX
    Replies: 4
    Last Post: 07-25-2015, 09:28 PM
  3. Are my subframe bushings bad?
    By HokieZHP in forum Mechanical | Troubleshooting
    Replies: 19
    Last Post: 04-18-2013, 01:58 AM
  4. Autocrossing Wheels
    By M0nk3y in forum Track and AutoX
    Replies: 63
    Last Post: 06-20-2011, 01:58 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •