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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, May-14-2015, 10:11:05 PM   #21
Amadeus
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Default Re: Subframe: Front vs. Rear mount brace

Quote:
Originally Posted by m3 hal View Post
Yes, the idea is that if you can get most of the load going to the rear mounts (via stiff rear bushings connected to a brace, and a softer bushing up front that will allow the rear to get most of the loading), you don't need to worry about the front because it is now seeing less load that the stock setup, and it doesn't have the ability to deflect as much and push up into the sheet metal. I have not done this to my car, but it sounds good in theory, I think.
Yeah this does sound good. By putting an aluminum bushing in the rear, there will be minimal upward deflection in the front. And the only way you can really get away with putting solid bushings in the rear is if you had a strong brace, which will be there. I think if you combined this with reinforcements in the front, there would be small likelihood of failure.

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Originally Posted by qualicas View Post
I reinforced front and rear subframe mounts. I ran bolts up from the existing threaded inserts through the trunk floor. Then I used a 6 x 6 x 0.75" thick sheet metal and riveted
that to the existing 0.032" thick top sheet metal. I used 3/16 stainless rivets. In the front I had to make welded pockets in the sheet metal so the nuts could hold to flat material.
Underneath I made my own reinforcing plates and epoxied them in place and riveted them as well. Now the forces are being distributed in a much larger area and twisting will be difficult because of the top reinforcing. It does seem few people ever do the front mounts from the top.
Do you have any pictures of this setup? With the direct connection from the bolt up through the trunk floor, where is the upward force now distributed? To the sides of your riveted sheet metal?

Vince, wow thats great! This is exactly what I wanted to see. Did those half cups you welded in interfere with any of the brackets used for the back seat? Do you have any more pics of the front setup?
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Old Thu, May-14-2015, 10:28:35 PM   #22
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Default Re: Subframe: Front vs. Rear mount brace

http://m3forum.net/m3forum/attachmen...2&d=1428640138
Picture of the rears. I did the fronts much like Vince but instead of welding I did a similar large piece of mild steel and riveted it in place. Spreads the load around better. I was frankly shocked to see all this metal is so thin.
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Old Thu, May-14-2015, 11:35:12 PM   #23
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Default Re: Subframe: Front vs. Rear mount brace

If the front points on the subframe push upwards, wouldn't the most important point of reinforcement be between the bushing the the mount plate? It would seem that reinforcing the front points from above (like the bolt through design) would only help for twisting action.

Take this picture for example. How does such damage occur? Is the main source twisting or compression from an upward force?
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Old Fri, May-15-2015, 05:34:42 AM   #24
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Default Re: Subframe: Front vs. Rear mount brace

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Originally Posted by mgp333 View Post
If the front points on the subframe push upwards, wouldn't the most important point of reinforcement be between the bushing the the mount plate? It would seem that reinforcing the front points from above (like the bolt through design) would only help for twisting action.

Take this picture for example. How does such damage occur? Is the main source twisting or compression from an upward force?
The damage is caused by a number of forces, both compressive and tension, in addition to torsional. Once the metal has fatigued through the constant application of these forces it will eventually fail and if left, the image above can occur.

We have never had a repeat failure or indeed initial subframe failure on a vehicle with our plate kit (Redish Motorsport) fitted.

The design process for our kit is well documented, it does an excellent job of preventing or indeed curing this problem.
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Old Fri, May-15-2015, 06:19:25 AM   #25
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Default Re: Subframe: Front vs. Rear mount brace

VinceSE2, nice work
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Old Fri, May-15-2015, 08:37:51 AM   #26
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Default Re: Subframe: Front vs. Rear mount brace

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Originally Posted by bithuizev View Post
The design above gets at the heart of the issue by distributing it directly to the frame rail.

Assuming you are talking about my design of the upper (I do have the Redish plates as well) rear mount, this is exactly my intention.
Without the bar, and its connection to the inner frame rail, much of the load is concentrated to the RACPs connection to the outer frame rail (wheel well), or taking a "detour" thru orher chassie components. The trunk floor for instance.


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Old Fri, May-15-2015, 08:40:32 AM   #27
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Default Re: Subframe: Front vs. Rear mount brace

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Originally Posted by kokgo20 View Post
VinceSE2, nice work

Thanks! I've been working on this design for quite some time.
Inspired by the Mason bars (great product, but i need my boot space) and some of the Redish solutions as well as James' videos and Petes numerous posts and comments.


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Old Fri, May-15-2015, 08:42:10 AM   #28
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Default Re: Subframe: Front vs. Rear mount brace

Quote:
Originally Posted by mgp333 View Post
Yeah this does sound good. By putting an aluminum bushing in the rear, there will be minimal upward deflection in the front. And the only way you can really get away with putting solid bushings in the rear is if you had a strong brace, which will be there. I think if you combined this with reinforcements in the front, there would be small likelihood of failure.







Do you have any pictures of this setup? With the direct connection from the bolt up through the trunk floor, where is the upward force now distributed? To the sides of your riveted sheet metal?



Vince, wow thats great! This is exactly what I wanted to see. Did those half cups you welded in interfere with any of the brackets used for the back seat? Do you have any more pics of the front setup?

Thanks, I'll post some more pictures and explanation later on.


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Old Fri, May-15-2015, 03:47:20 PM   #29
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Default Re: Subframe: Front vs. Rear mount brace

VinceSE2 - I was trying to think of what else one could do to brace the fronts while still preserving the functionality of the rear seats and it seems like your solution is probably the way to go. That in addition to the reinforcement plates underneath. I assume those cups didn't affect anything when you put the seats back in?
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Old Fri, May-15-2015, 04:37:58 PM   #30
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Default Re: Subframe: Front vs. Rear mount brace

While I'm in the midst of this project and haven't installed the back seat yet, i see no reason there would be any space issues.
Basically all I have added is "behind" the sheet metal wall I removed.

The idea is to stabilize the threaded insert such that it does not break loose from the top mounting surface when the tilting/bending force is applied to it.
The bolt going thru the threaded sleeve, and the nut and washer on top is one part of the design. The pipe and its floor (which is welded against the top of the threaded sleeve is another. And finally the pipe itself is welded to the inner skin of the body adding more support against the tilting.
The pipe is a 2" exhaust pipe with 2mm thick walls.
The hole saw is 51 mm OD.

Hera are some more pics:




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Discussing Subframe: Front vs. Rear mount brace 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)