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E46 M3 (2001-2006) Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006.


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Old Thu, Mar-02-2017, 12:52:29 AM   #21
AussieE46M3
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Default Re: Ordered AKG solid subframe mounts and they emailed me back......

Hi JO3M3,

You're pretty much on the money there. With repair plates I couldn't imagine stock bushings would be as critical as without.
Still technically reasonable force on a small area however, with increased material thickness and the multi layer affect as well as not directly atop heated affected zones I would not be concerned.

They sure are WyattH the reasoning for that is as I said earlier. I linked a picture to emphasise the difference. Couldn't ever see that having the issues we do.

Quote:
You'll notice on newer BMW's the subframe mounts are as wide and long as possible and directly mounted to the chassis rails unlike the E46. by increasing the perpendicular distance from the applied moment centre the force at the mount point is reduced. (T=F*d).
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Old Thu, Mar-02-2017, 12:58:17 AM   #22
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Default Re: Ordered AKG solid subframe mounts and they emailed me back......

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Originally Posted by J05M3 View Post
After thinking about this a bit, if I were to use say the redish plates in addition to your or Vince's solution, then the surface area gain of solid subframe bushings would be negated because the load is already spread over a larger area on the RACP because of the plates. In that case it would be best to stick with OEM sub bushings because the pressure pts or load is no longer felt on the racp at the normal factory locations but rather the plates and their new distributed locations. This way, the overall force on the RACP would be dampened by oem rubber and the whole surface area argument of sold subframe bushings is null. Does this line up with what you are saying?
This is, and has always been, precisely my line of thinking and is exactly what I did.

Contrary to popular belief, I've never thought the OEM bushings were the problem. Rather, the thin metal and poor load path are the true issue(s). The front OEM bushings' lips only highlight the underlying problem.

Further, logic tells us that while a solid bushing will indeed spread the load at the mounting point, it will also dramatically increase the spikes in load and so this just seems..... well.... like a bad idea to me. You might gain localized strength but compromise the overall structure more. Just conjecture, of course, but food for thought.

Surely with a Vincebar/bolt-through fronts this is probably a moot point, though. But the flip side of that is that once properly reinforced, why go solid at all? Why not enjoy the smooth and quiet OEM bushings that are built like tanks and last forever?
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Old Thu, Mar-02-2017, 01:00:15 AM   #23
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Default Re: Ordered AKG solid subframe mounts and they emailed me back......

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Originally Posted by J05M3 View Post
Again this is contrary to what some, of what I consider experts on RACP damage, recommend. One of the most common cracks of the RACP originates from a pressure point caused by contact with the OE subframe bushing. Solid subframe or even poly subframe bushings help to alleviate this pressure because of the contact surface area with the RACP is greater and not concentrated over a spot weld where that crack originates.

Edit: Didn't realize you are the other new subframe mount solution person until I looked at your name after posting. What you are saying is different then what Vince is saying unless I am missing something
Think of it this way... it doesn't f*cking matter. The problem isn't bushings pushing *against* the chassis of the car, it's the bolt/ bushing pulling the carrier inside the chassis *out* of the car.

The more direct and violent that force is (hammer vs rubber mallet), the harder it will be on the car. 95A is going to be plenty on a street car, anyhow
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Old Thu, Mar-02-2017, 01:06:05 AM   #24
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Default Re: Ordered AKG solid subframe mounts and they emailed me back......

Hi Eric,

you're correct. Both the chassis and bushings were designed by BMW. You'd think they would be more compatible. The mounts should have been locally thicker to avoid distortion and any joining welds not been beneath them.

Even with bracing like my own kit or Vince's I still would not recommend solid bushings. The rears may be capable however, a bolt going through the front mount would help with tensile (down) but not compressive forces (up) that are applied through the bushing to chassis interface, not the restraining bolt.

A roll cage above the mounts could absorb the compressive loads an distribute them through the triangulated structure to all the other structural pickups however, a small sheet and chamfered tube I believe, could not.
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Old Thu, Mar-02-2017, 01:30:01 AM   #25
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Default Re: Ordered AKG solid subframe mounts and they emailed me back......

Quote:
Originally Posted by EricSMG View Post
This is, and has always been, precisely my line of thinking and is exactly what I did.

Contrary to popular belief, I've never thought the OEM bushings were the problem. Rather, the thin metal and poor load path are the true issue(s). The front OEM bushings' lips only highlight the underlying problem.

Further, logic tells us that while a solid bushing will indeed spread the load at the mounting point, it will also dramatically increase the spikes in load and so this just seems..... well.... like a bad idea to me. You might gain localized strength but compromise the overall structure more. Just conjecture, of course, but food for thought.

Surely with a Vincebar/bolt-through fronts this is probably a moot point, though. But the flip side of that is that once properly reinforced, why go solid at all? Why not enjoy the smooth and quiet OEM bushings that are built like tanks and last forever?
I had originally wanted to stick with OEM, until people started telling me to go solid. Though, solid just didn't make sense in a logical way. OEM comforts my hyper analytical mind, solid never did.
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Old Thu, Mar-02-2017, 01:33:18 AM   #26
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Default Re: Ordered AKG solid subframe mounts and they emailed me back......

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Originally Posted by Drewster View Post
Think of it this way... it doesn't f*cking matter. The problem isn't bushings pushing *against* the chassis of the car, it's the bolt/ bushing pulling the carrier inside the chassis *out* of the car.

The more direct and violent that force is (hammer vs rubber mallet), the harder it will be on the car. 95A is going to be plenty on a street car, anyhow
I disagree and believe it f'ing matters when you are discussing something that still seems to contain multiple points of view on what many consider to be a contribution to the solution. I am not the type of person to just move on after one explanation. I always need to know why.
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Old Thu, Mar-02-2017, 01:39:52 AM   #27
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Default Re: Ordered AKG solid subframe mounts and they emailed me back......

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Originally Posted by J05M3 View Post
I disagree and believe it f'ing matters when you are discussing something that still seems to contain multiple points of view on what many consider to be a contribution to the solution. I am not the type of person to just move on after one explanation. I always need to know why.
I'm not saying don't ask/ debate it to your heart's content, I'm saying it doesn't f*cking matter how your subframe mounts "distribute" force.. because the area of the mount has nothing to do with the carrier trying to rip *out* of the chassis
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Old Thu, Mar-02-2017, 01:40:46 AM   #28
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Default Re: Ordered AKG solid subframe mounts and they emailed me back......

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Originally Posted by J05M3 View Post
I had originally wanted to stick with OEM, until people started telling me to go solid. Though, solid just didn't make sense in a logical way. OEM comforts my hyper analytical mind, solid never did.
Solid mounts have never been a consideration for me as I refuse to believe that comfort isn't notably decreased. Might I be wrong? Of course! But in this case ignorance truly is bliss as the OE bushings are fab-u-lous from a road-car point of view and I see nothing to gain by going aftermarket.

BUT - comfort aside, solid does seem counterproductive in that some give is important in some places.

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Originally Posted by Drewster View Post
I'm not saying don't ask/ debate it to your heart's content, I'm saying it doesn't f*cking matter how your subframe mounts "distribute" force.. because the area of the mount has nothing to do with the carrier trying to rip *out* of the chassis
Exactly! The main problem is pulling away and no bushing is going to matter here.
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Old Thu, Mar-02-2017, 01:41:34 AM   #29
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Default Re: Ordered AKG solid subframe mounts and they emailed me back......

I thought I had it all figured out. I even ordered solid. AKG emails and says they don't recommend it and now this thread. Now I feel like going 95a
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Old Thu, Mar-02-2017, 01:44:07 AM   #30
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Default Re: Ordered AKG solid subframe mounts and they emailed me back......

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Originally Posted by Drewster View Post
I'm not saying don't ask/ debate it to your heart's content, I'm saying it doesn't f*cking matter how your subframe mounts "distribute" force.. because the area of the mount has nothing to do with the carrier trying to rip *out* of the chassis
Isn't that a separate part of the issue though. Yes the RACP wants to rip out because of the forces applied to it, but there is also cracking that happens directly where the front oe bushings makes contact with a spot weld. Two different symptoms of the same problem.
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Discussing Ordered AKG solid subframe mounts and they emailed me back...... in the E46 M3 (2001-2006) Forum - Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006. at BMW M3 Forum.com (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)