E46 Fanatics Forum banner
  • Hey everyone! Enter your ride HERE to be a part of this month's Ride of the Month Challenge!
21 - 40 of 44 Posts

·
Registered
2000 323Ci coupe manual
Joined
·
412 Posts
If using a Venn diagram to explain, the variables are date of manufacture (earlier date worse), transmission type (manual worse), and power of engine (stronger worse).
 

·
OEM ///PLUS
2003 M3 6MT Slicktop
Joined
·
23,841 Posts
1) Is my 2005 330Ci vulnerable to the issue, or is it pre-2001 M3s and to a lesser extent 330s?
2) If it is what should I do? I've got the radical, and probably radically expensive option 1), or the slacker-ish option 2). Or a compromise option 3)
ok been explaining this stuff on forums for like 14 years now.
1) yes your year car E46 “could” have an issue. *like all E46s. And yes your year/model is to a much lesser extent. the revisions helped.
i’ve seen it more about abuse and environment than anything at this stage. *exception the early 323/328 RACP is highly susceptible because of the internal thread “block/receptacle” mounting and metal.
2) 3!
i would visually inspect for cracks. but it’s likely you’ll never have an issue needing immediate repairs. 90% here always proclaim they’ll keep their car forever but we see that does not happen often. but if you are it would not hurt to reinforce it. Vince Bar is great design, but more for bullet proofing the car that’s high HP or tracked. if time and money were not a factor that is the one I would suggest. preventively most could just do the BMW expanding epoxy in crevice to secure metal and be fine.
 

·
OEM ///PLUS
2003 M3 6MT Slicktop
Joined
·
23,841 Posts
If using a Venn diagram to explain, the variables are date of manufacture (earlier date worse), transmission type (manual worse), and power of engine (stronger worse).
data shows Transmission doesn’t really matter.
ABUSE matters. RUST matters.
 

·
Registered
Joined
·
30,040 Posts
Chalk it up to a bad design by BMW. Too narrow mounting points causes excessive repeat loading of the floor space. Band-aids/fixes can mitigate/delay damage. Adding more metal/weight/reinforcements (Redish, turner etc) can delay further, likely indefinitely. Just a lot of trouble to go through. The E46 was a continuance of the E36 which was an old design that had issues too. E90 and beyond did not have this issue due to the wide(r) path subframe design that pretty much all RWD cars have today. Sadly the E46 did not copy the E39 design for whatever reason. Maybe packaging, development cost, handling feel. Who knows.

But as said, all E46 cars can experience this.

From what I remember in the old days, someone found evidence BMW added a few more spot welds in revised/newer sheet metal floor vs. the old ones, but kept the same part #. Like a hidden update/change. Though no one really officially confirmed that.
 

·
Registered
2005 BMW 330i
Joined
·
837 Posts
Doesn't bushing age and condition have a lot to do with it?
 

·
Registered
Joined
·
30,040 Posts
Probably not. if anything that might even prolong the failure as shock is less directly transmitted to the steel.

unless the bushing is completely gone and the shock is transmitted too abruptly.

Short answer is it could, but probably not.
 

·
Registered
2005 BMW 330i
Joined
·
837 Posts
Cuz that's what I've been hearing form a bunch of race shops and high end BMW shops that do M3 rear subframe reinforcements on the daily. Is worn out bushings put more strain on the subframe because there's nothing to absorb shock.
 

·
Registered
Joined
·
30,040 Posts
Depends on where on the spectrum the bushing is at in terms of wear. Really that thought exercise is moot as 1) bushings should be replaced anyway on an old performance oriented car and 2) the failure is ultimately inevitable regardless. Just a matter of driving habits + time
 

·
Registered
Joined
·
30,040 Posts
light to moderate worn bushing=soft. think about it, people replace bushings cause response is gone. response means less firm.

less firm means less direct of a load.

bushing completely gone then metal on metal. but then that would be obvious.

edit but yes def replace all bushings anyway. good for the car
 

·
OEM ///PLUS
2003 M3 6MT Slicktop
Joined
·
23,841 Posts
Doesn't bushing age and condition have a lot to do with it?
Yes they absolutely are a contributing factor.
once the bushings get slop they allow impacts that can cause cracking.
 

·
OEM ///PLUS
2003 M3 6MT Slicktop
Joined
·
23,841 Posts
From what I remember in the old days, someone found evidence BMW added a few more spot welds in revised/newer sheet metal floor vs. the old ones, but kept the same part #. Like a hidden update/change. Though no one really officially confirmed that.
oh it’s been confirmed for many years. I posted some of these when my 323Ci panel was completely replaced ten years ago.
the changes/revisions have been mentioned throughout this thread. it’s not just welds.

you’re lucky you don’t have to worry about this issue on another car. I’d probably forget (on purpose) too 😉
 

·
Registered
Joined
·
301 Posts
Solid subframe bushings can help, but in the end you need something like the Vincebar or a X-Brace to completely fix the issue by redirecting the load path.
 

·
OEM ///PLUS
2003 M3 6MT Slicktop
Joined
·
23,841 Posts
Solid subframe bushings can help, but in the end you need something like the Vincebar or a X-Brace to completely fix the issue by redirecting the load path.
you’ll find that even the companies that make solid subframe bushings recommend doing so only if you have at least done underside plates.

solid metal don’t absorb the initial impacts and put more force on the mounting studs/blocks.

the consensus is new/upgraded subframe bushings on stock E46 floor panel. solid if reinforced.
 

·
Registered
Joined
·
301 Posts
you’ll find that even the companies that make solid subframe bushings recommend doing so only if you have at least done underside plates.

solid metal don’t absorb the initial impacts and put more force on the mounting studs/blocks.

the consensus is new/upgraded subframe bushings on stock E46 floor panel. solid if reinforced.
I disagree, solid subframe bushings will spread out the load across all mounting points more evenly, essentially acting as a sort of reinforcement from the bottom. It's been a known fact for almost as long as the issue has persisted now. The solid subframe bushing solution was pioneered by MK Motorsport in Germany way back in the day.

Some people even forego top side reinforcement completely if their RACP is in perfect shape and opt to only do solid subframe bushings. Personally I wouldn't do that, but it is an option that I've seen some track car owners go for.

Obviously you'd still want plates if you have major cracks that need to be patched up. The "band aid" descriptor really does apply. Just like you obviously should stop-drill and weld existing cracks when installing any top-side reinforcement.
 

·
OEM ///PLUS
2003 M3 6MT Slicktop
Joined
·
23,841 Posts
I disagree, solid subframe bushings will spread out the load across all mounting points more evenly, essentially acting as a sort of reinforcement from the bottom.
issue is the stock rubber engineered bushing is made to absorb impact stress(forward/back). like one sees at take off. take this out and those same forces have to go somewhere. on the mounting studs and receiver block.
Read this 4 part series by CMP, it explains everything you need to know: Technical
maybe the quickest way is to quote the very same place you posted earlier. go to “Cons of Solid Bushings”, then go to around the 7th paragraph after he explains the forces that change because of eliminating the rubber engineered bushing. i won’t quote all the paragraphs, you can read and see if you don’t have a different perspective afterwards.

By reducing the dampening of “impulsive forces” you increase the peak stress acting on the chassis thus reducing the fatigue life. Meaning, failure is both more likely to occur and occur sooner.
 

·
Registered
E30M3 Race F10 535 R1150Rt M Coupe
Joined
·
6,789 Posts
Ahhh, just put a Ford 9” solid rear axle in the beast and be done with it! /s

Rust never sleeps.
Ah but I migrated away from leaf springs and Lakewood traction bars decades ago....

"Neil Young", BTW.

I'm in the camp of rubber mounts=less damage. From my side of the service bay (practical assessment/cause-effect) evaluation.
 

·
Registered
Joined
·
301 Posts
issue is the stock rubber engineered bushing is made to absorb impact stress(forward/back). like one sees at take off. take this out and those same forces have to go somewhere. on the mounting studs and receiver block.

maybe the quickest way is to quote the very same place you posted earlier. go to “Cons of Solid Bushings”, then go to around the 7th paragraph after he explains the forces that change because of eliminating the rubber engineered bushing. i won’t quote all the paragraphs, you can read and see if you don’t have a different perspective afterwards.

By reducing the dampening of “impulsive forces” you increase the peak stress acting on the chassis thus reducing the fatigue life. Meaning, failure is both more likely to occur and occur sooner.
I still disagree with their assessment. You can view this video of a subframe with very worn bushings to illustrate my point:


You can see the movement that is basically trying to tear out the subframe bolts. These forces/movements also exists with new rubber bushings, and are a large contributing factor to RACP cracking. Solid subframe bushings essentially eliminate this movement, thereby reducing cracking from metal fatigue.
 
21 - 40 of 44 Posts
Top