cracked subframe

[Trawler]

It amazing me that some people think the BMW repair is a better option than welding in plates and stop drilling the cracks. BMW put the same Sh1te back in that broke in the 1st place, and as what's happening in the op's case in should just about last 10years so they don't really give a sh1t after that!! Also some of the people who work at BMW main dealers I would'nt let work on my kids push bike never mind a csl.
OP take it to Redish or there's others who can fix it properly (there's more options than just plates)

If I remember correctly NZ_M3 a few years back posted a good write up why plates do not work. The foam injection was also discussed.

[Chad]

Personally with high expectations regarding service histories etc on the Csl, buyers would expect repairs to be done buy BMW, any other repairs could possibly knock valves, But nothing wrong with useing polyfilla :thumbs:

[GregorFuk]

Personally with high expectations regarding service histories etc on the Csl, buyers would expect repairs to be done buy BMW, any other repairs could possibly knock valves, But nothing wrong with useing polyfilla :thumbs:

Great to have faith in BMW.

[Mike RT4]

It amazing me that some people think the BMW repair is a better option than welding in plates and stop drilling the cracks. BMW put the same Sh1te back in that broke in the 1st place, and as what's happening in the op's case in should just about last 10years so they don't really give a sh1t after that!! Also some of the people who work at BMW main dealers I would'nt let work on my kids push bike never mind a csl.
OP take it to Redish or there's others who can fix it properly (there's more options than just plates)

The BMW repair IS better than the welding of plates (IF the injection of the resin isn't carried out as well)....

If you look at any repair that has been done with just plates and you understood why it cracked in the first place, you would also understand why just welding plates on is even more of a disaster than the original problem....

[Chad]

Great to have faith in BMW.

BMW are good for somethings. If csl wasn't what it is ,and just a £7k e46 m3 I'd have no problems with tin foil and polyfilla repair, as I do 99 percent of my own maintenance anyway :thumbs:

[GregorFuk]

BMW are good for somethings. If csl wasn't what it is ,and just a £7k e46 m3 I'd have no problems with tin foil and polyfilla repair, as I do 99 percent of my own maintenance anyway :thumbs:

A little harsh

https://youtu.be/09mqQRcAPds

[select]

The BMW repair IS better than the welding of plates (IF the injection of the resin isn't carried out as well)....

If you look at any repair that has been done with just plates and you understood why it cracked in the first place, you would also understand why just welding plates on is even more of a disaster than the original problem....

How come? As said earlier, BMW just replaces the cracked subframe with a new one while the issue remains. Its a fact that new cracks developed after BMW replaced the subframe. On the other hand i have not seen one subframe fail after its been reinforced with good plates and got uprated bushings.

I would like to hear your opinion on what you think is the issue, why the subframe cracks.

[Chad]

For a bit of fun let's put it to a vote. BMW new floor pan. Verses welding plates. My vote goes to BMW fix. But I'm not against welding plates for cheaper fix. :thumbs:

[select]

My Point is, a new floor pan from BMW is no fix at all.

[Trawler]

If anyone is interested

https://nam3forum.com/forums/forum/csl-register/general/csl-technical-area/524206-subframe-poll

[select]

Yes, thats exactly what happens if you stay with stock bushings.

To use his analogy.

Using the BMW repair = Simply Replacing the coke can with a new one., it just delays the "cracking process" which will inevitably happen.

The point is, to drill and weld the cracks that are there and they will be on nearly all csl with 60.000 miles. Even 316i have this problem, so its not only affecting cars which are driven hard. And reinforce the structure with the plates, whichs point is, to distribute the induced load via a bigger area. But the key thing is, to replace the squishy stock bushings with delrin or even solid ones, to stop the load from even ocurring. Like BMW did with from factory with M3 GTS and F8X M4.

See this video of an Camaro, which has the same issues.

https://www.youtube.com/watch?v=6yOz--DIuIc

[Mike RT4]

My Point is, a new floor pan from BMW is no fix at all.

YES IT IS. BMW don't just replace the floor plan, do your research :blalalala:.

If you JUST weld plates to the "coke can" floor plan (as you have pointed out) - it WILL just crack around the welds of the plates and rip out the ENTIRE floor section around the plates :bigcry:.

The BMW repair replaces the entire floor section with a new item, but the key part to their repair is to fill the void with a special resin that links the two floor parts together to create a honey-comb effect (which makes the boot floor and sub frame mount much stronger than the sum of their parts - in the same way it does for composite sheets).

The main problem is the holes for the subframe bolts are just too big and allow a yawing motion that causes the cracks. Spoon actually do some "Rigid Collars" for the E46 M3 that effectively plug the holes and allow the precise location of the bolts which will prevent the yawing motion. I don't really understand why more people haven't fitted these.

Here is a video that shows them on another car, but the principle is the same :

https://www.youtube.com/watch?v=zWyUD6UXfog

I would hasten to add that MOST legitimate repairers understand this and weld the plates in conjunction with the resin injection. If they do NOT, then walk away!

[select]

I know they inject foam too. Funny enough they didnt until they were faced with lawsuits they started to inject foam.

Still its a Bandaid.. as it doesnt fix the issue. It merely strengthens the chassis to be able to withstand it. For what amount of time? Nobody knows, i decided for myself that i didnt want my csl to be a testbed for BMW, so i used what is proven to fix the issue.

Regarding the rigid collars i think i have read about that solution in the past.
But its not very widespread this.

[MisterCorn]

Yes, thats exactly what happens if you stay with stock bushings.

To use his analogy.

Using the BMW repair = Simply Replacing the coke can with a new one., it just delays the "cracking process" which will inevitably happen.

The point is, to drill and weld the cracks that are there and they will be on nearly all csl with 60.000 miles. Even 316i have this problem, so its not only affecting cars which are driven hard. And reinforce the structure with the plates, whichs point is, to distribute the induced load via a bigger area. But the key thing is, to replace the squishy stock bushings with delrin or even solid ones, to stop the load from even ocurring. Like BMW did with from factory with M3 GTS and F8X M4.

See this video of an Camaro, which has the same issues.
https://www.youtube.com/watch?v=6yOz--DIuIc

I would have assumed that the bolts provided a clamping force, and that the subframe was held in place by this force. Is this suggesting that there is actual yaw movement on the subframe when it is mounted in the car? Seems unlikely to me. I have read about these for the NSX but the word from those that know was that they were not needed and that the hole sizes were like they are for production tolerances.

MC

[Mike RT4]

I know they inject foam too. Funny enough they didnt until they were faced with lawsuits they started to inject foam.

Still its a Bandaid.. as it doesnt fix the issue. It merely strengthens the chassis to be able to withstand it. For what amount of time? Nobody knows, i decided for myself that i didnt want my csl to be a testbed for BMW, so i used what is proven to fix the issue.

Regarding the rigid collars i think i have read about that solution in the past.
But its not very widespread this.

The correct permanent fix would be the BMW repair and the installation of the Rigid Collars.

Welding of plates will NOT fix the issue any more than doing just the BMW repair, it is the exact same band-aid. The yawing motion of the bolts (more prevalent in SMG equipped cars due to the shockloading the automated gear changes in the faster modes transfer to the diff and hence the subframe mounts) is the issue and so you have to remove this. Obviously anything else that helps lesson this movement is going to increase the amount of time it takes to re-occur, but not prevent it (so still a band-aid).