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Reinforced Subframe EPIC Failure

184K views 175 replies 65 participants last post by  79conman 
#1 ·
This subframe is reinforced with the standard HPF reinforcements...**** :banghead:

Car is at VAC Motorsports atm.










 
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#93 ·
Thanks for info! This helps me a lot!

So you first you cut out the top floor, weld the floor, and then the beam to what is a honneyomb structure? For me, it looks like the beam is lying on some sort of ordinary sheetmetal but i understand this is some sort of honneycomb? Or is the honneycomb you are talking about filling the 150 mm gap, and then you remove it so the beam can take its place?

:) After drilling, did you make threads all the way through from the underside? And do you remember aprox. Length and diameter of the bolts?

I can try posting som pictures when its done! :)

And is there anything else in particular i need to look out for?

Thank you again! You really don't understand hos much this helps! :)
 
#94 ·
So you first you cut out the top floor, weld the floor, and then the beam to what is a honneyomb structure? This is correct.

For me, it looks like the beam is lying on some sort of ordinary sheetmetal but i understand this is some sort of honneycomb? Or is the honneycomb you are talking about filling the 150 mm gap, and then you remove it so the beam can take its place? It is ordinary sheet metal. It's just constructed into a honeycomb/box section design between the boot floor and the underside of the car filling the gap as you said. You don't remove it you just weld the brace to it and the boot floor to it.

After drilling, did you make threads all the way through from the underside? And do you remember aprox. Length and diameter of the bolts?
We dropped the bolts in from the boot side. If you look at the brace you can make out the bolt heads. So the subframe underneath gets the nyloc nuts. The reason it's better to do it this way is the bolt head holds on the side of the brace when you drop it in place so you can still drop out your subframe with one person under the car. You don't need a spanner and a person in the boot to remove it. Sorry I don't remember the bolt sizes in length but diameter we did the same as the factory bolt in the floor which by memory is 10 or 12mm. Just check that. Then you don't have to change/drill subframe bushes. It stays factory sizes.

Other than that everything should be good. Definately post up some pictures when you do it. The more info on here the better.

Hope the explanation is ok and I'm not confusing you at all. It's always a bit hard to get all the info across correctly over the internet.
 
#95 · (Edited)
This might help as well.





Also have a look on page 4 of this thread. There is some close up photos to show a bit more detail.
 
#97 ·
No. When I say honeycomb i'm talking about the design of the box section of steel that is found in there. Lets just call it box section then ok. There is nothing to eat in my car ;)
 
#99 ·
I Get it! :) good picture! You say you drop the bolts through. :) That mens the entire load is distributed through the head of the bolt, and into the beam and through it to the points where it connects to the car.

Just thinking, but would it not be stronger if you make threads through the floorsection to distribute the load to an even greater area? Through the beam and the original mountingpoints for the subframe. Without threads all the way i guess assembly and removal is significantly easyer + im sure the beam is significantly stronger than the bolts... However this wil probably be a high hp car someday so i want this to be bulletproof! :)

Maybe I willy make a DIY if I'm pleased with the result :)
 
#100 ·
Yes all the load is through the beam and the bolt and on top of the chassis rails. That is the whole design and that is where you want to load. It is 100x stronger than standard. You get no advantage threading the length of the bolt. Everything is welded together. Nothing is going to move now and the beam and the bolt are manufactured to take a lot more load than this.

And considering my car is a built engine, turboed and I hang it off the launch control at 5000rpm with 18psi boost and side step the clutch I think I've tested the strength for what you want to do to your car ;)
 
#104 ·
lol there wasn't much design to it. Just some lateral thinking and a little bit of engineering knowledge and build it. From the time we found the floor pulling apart to the time we finished the job it was 4 hours. And I did this job and posted it on a public forum 5-6 years ago. So it wouldn't suprise me if it's got around other workshops. Not that I care. That's why I share the info. Helps others out.
 
#109 ·
That's fine in mild steel. Don't even need 40mm wide mine is 60x30mm.
 
#112 ·
I have the HPF kit on order, I'm debating what other than the subframe/diff bushings I should get done at the same time.
My guy that's doing the work said that being honest, he isn't a fabricator, and doesn't want to attempt something like this.
Trying to figure out if/where I should get this done :hmm:
 
#113 ·
I know this is a stupid question, but what should i be looking for while DRIVING the car to be able to tell if the subframe is toast. I got under the car a few weeks ago and there is a hairline crack. And of course it can only get worse... I didnt see anymore but one crack. Although i didnt remove the dif/look in the trunk.

What are tell tale signs? I hear this little rattle going over bumps but it sounds like a heat shield/exhaust hanger or something. It just sounds to thin......looking at this now im worried hahaha
 
#116 ·
Would you suggest getting a reinforcement kit? Or welding something serious in? Whats the average $ amount i can expect to dish out for a QUALITY job?
 
#121 ·
HPF kit is better than any other kit. get theirs.

Cost depends on a lot of things. Its a GOOD idea to replace ball joints and almost anything with wear as long as you have things apart. It a good time to install adjustable rear CAMBER arms if you have coil over suspension.

If you have NA power you can stay with the stock sub frame bushings although it is a good time to RENEW them while you have everything apart. Other choices are AKG RED or BLACK poly sub frame bushings. Never use Poweflex YELLOW poly subframe bushings. They have been shown to not FIT properly and tear. Consider AKG red poly RTABS depending on your needs.

Total cost is a rock bottom of 800usd to over 2k depending on options PLUS the price of the HPF plate kit.

I have heard of group pricing cheaper than this. It so much depends on what shops are available, what part of the country you live in and so on.
My cost was 2k with all new poly sub frame bushings,all new rear ball joints and lots of additional welding beyond the normal plate install...plus the price of the HPF plate kit. I already had RTABS and rear camber arms.
You want to inspect your GUIBO and front differential mount too!
 
#118 ·
Can i just rip out the trunk liner and check everything out? I know i wont be able to see where the mounts are. But its worth a look, no?
 
#120 ·
The pictures on the past pages are a view point from the trunk i thought?
 
#122 ·
The man. Thanks for that dude, project acquired!
 
#125 ·
hello.
I drive a BMW 99, 323i. I've been lurking here occasionally :hi:. Iv been quite surprised how much you guys spend on reinforcement subframes :yikes:.

Thought i will share with some photos from time i have done reinforcement.
Everything was done at garage, exept pressing in new bushings ;), and the price for all in total was 150$ :shhh:.
The plates was not only from bottom of the car , but from inside as well(you can see the shape of the metal plate on one of the photos).
Sorry for my english, its my 3 language. :tsk:.
 

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#137 ·
Over torqueing would only snap the bolt.
Force takes the path of least resistance, and the subframe mounts are subjected to infinite many load changes through its life. When one point starts to go or one bushing starts to fail, load on the remaining points increase.

That it the way the cookie crumbles. Don't hope for the best. Just get in there and fix everything, and don't try do do a minimum.
 
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