lots of info at the bottom. please read (everyone).
Originally Posted by
az3579
Don't worry about it.
why?
Originally Posted by
Dual
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.
Originally Posted by
fw_fw
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.
Originally Posted by
sillieidiot
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.
Originally Posted by
toddztoyz
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
2004 330i ZHP
2005 330iT ZHP
2010 328iT M Sport