subframe fixes

[Niel333]

I managed to get resin but its coming from Germany and its going to cost me to get it here, do I have to get 2 for just a left side crack or is one enough?

[s.mac]

looks like the suspension could do with cleaning, greasing and springs powder coating :whistle:

Gareth how much do BMW charge to apply the resin to the correct places??
not sure I would DIY

[monkeycsl]

I voluntarily fitted the BMW official epoxy fix into my car - even though mine has no cracks - quite simply because if you've seen the way the rear floor is designed you will realise that having such a large void space in between the sheet metal that forms the rear floor exacerbates torque stress transfer - and overtime it will tear it out.

Personally I am not a fan of welding extra plates into the rear floor (rust proofing is a big issue as there are areas you simply can't get to) - I've seen failures even with the plates in place - this is because it is a band-aid fix versus a load transfer fix.

By filling the void within the floor space transfers the torque load to a much larger area and most importantly above the floor to the secondary sheet metal that forms the ridge carrier - further the epoxy used has a dampening effect as it is not completely solid. It is a proven product used in Formula 3 race car suspension repairs.

I also don't believe in having a larger subframe bushing footprint helps - as this is no different to having a larger washer in between the subrame and the floor.

The problem is more related to the floor having a void thus allowing it to flex more so than the foot print of the mounting.

I can tell you for a fact that having the epoxy in the floor makes a very noticeable difference to the rear floor rigidity - and that's in a car with KW race 2 ways and 14kg/mm springs. I am not the only CSL owner in NZ with this in the floor and all have noted how noticeably different the rear felt post the epoxy install.

I agree with the solid bushes not helping to damp the forces but the bmw bushes appear to have a raised lip around the edge which seems to put excess pressure in a small surface area,why are they not flat to mate upto chassis?Do you think if there is no crack then the resin both sides will stop further cracks appearing?:notworthy:
Also you said you did both sides is it a repeat of first step and do you have to drill a 10 mm hole on offside as there is not one there like on the nearside hope this makes sense cheers.

[NZ_M3]

Christ Duncan that doesn't look too good. The other car I spoke about earlier in the post where the whole floor came apart had exactly the same type of body fractures like yours - are you running solid rear subframe mounts? :bigcry:

Unforunately Duncan, your car is a good illustration of what I have been saying for a while - that the stress cracks aren't isolated to the mounting floor pan itself - i.e. it is to do with the load being carried incorrectly through the body structure, cause premature fatigue fractures (i.e. the void in the bottom floor sheet metal).

I'd get that welded up ASAP before it drops the whole floor out of the car (which it will).


Neil333 - one tube is enough to do both rear mounts - If you are doing the fronts, then you need two.

I agree with the solid bushes not helping to damp the forces but the bmw bushes appear to have a raised lip around the edge which seems to put excess pressure in a small surface area,why are they not flat to mate upto chassis?Do you think if there is no crack then the resin both sides will stop further cracks appearing?:notworthy:
Also you said you did both sides is it a repeat of first step and do you have to drill a 10 mm hole on offside as there is not one there like on the nearside hope this makes sense cheers.

I honestly don't believe the raised lip has anything to do with the fractures - this is not an impact failure where the bushes are moving around so much that they are pulling out of the chassis - but rather a torque load transfer being carried incorrectly through the car causing premature fatigue stress fractures. Like I said, if the lip had anything to do with it, then a quick and easy fix by BMW would have been to simply wack a couple of 3mm washers in between the subframe and the chassis floor - they haven't done that because it is not related to it. Just look at the way Duncan's car is coming apart.


You only drill one hole - in the middle of the floor ridge - the resin is injected into pre-existing holes on the left and right side of that (not the first layer, but the second layer skin - lot of people get this wrong and inject it into the incorrect cavity space).

The link you posted where the guy cut open the sound proofing is incorrect - he was trying to get to the front mounts also - you actually get to those through the front seatbelt mounts - the rear mounts are done through existing holes in the chassis floor (covered by plastic bungs).

[monkeycsl]

Christ Duncan that doesn't look too good. The other car I spoke about earlier in the post where the whole floor came apart had exactly the same type of body fractures like yours - are you running solid rear subframe mounts? :bigcry:

Unforunately Duncan, your car is a good illustration of what I have been saying for a while - that the stress cracks aren't isolated to the mounting floor pan itself - i.e. it is to do with the load being carried incorrectly through the body structure, cause premature fatigue fractures (i.e. the void in the bottom floor sheet metal).

I'd get that welded up ASAP before it drops the whole floor out of the car (which it will).


Neil333 - one tube is enough to do both rear mounts - If you are doing the fronts, then you need two.




I honestly don't believe the raised lip has anything to do with the fractures - this is not an impact failure where the bushes are moving around so much that they are pulling out of the chassis - but rather a torque load transfer being carried incorrectly through the car causing premature fatigue stress fractures. Like I said, if the lip had anything to do with it, then a quick and easy fix by BMW would have been to simply wack a couple of 3mm washers in between the subframe and the chassis floor - they haven't done that because it is not related to it. Just look at the way Duncan's car is coming apart.


You only drill one hole - in the middle of the floor ridge - the resin is injected into pre-existing holes on the left and right side of that (not the first layer, but the second layer skin - lot of people get this wrong and inject it into the incorrect cavity space).

The link you posted where the guy cut open the sound proofing is incorrect - he was trying to get to the front mounts also - you actually get to those through the front seatbelt mounts - the rear mounts are done through existing holes in the chassis floor (covered by plastic bungs).

Thanks for that will do both sides. did you do front part too.I also heard the audi rs4 battery tray gets same treatment with the two part epoxy and its half the cost of the bmw stuff but prob a different type so wont risk it cheers again.

[azrael]

I think BMW should be doing this as a preventative fix. If people do it themselves and get it wrong I'm sure BMW would use that as an excuse.

[DuncanR]

looks like the suspension could do with cleaning, greasing and springs powder coating :whistle:

You are joking mate !!! :birdman:

- are you running solid rear subframe mounts? :bigcry: Just OEM with limiters .. I think.

Unforunately Duncan, your car is a good illustration of what I have been saying for a while - that the stress cracks aren't isolated to the mounting floor pan itself - i.e. it is to do with the load being carried incorrectly through the body structure, cause premature fatigue fractures (i.e. the void in the bottom floor sheet metal).

I'd get that welded up ASAP before it drops the whole floor out of the car (which it will).Good job I sit up front then !:119:

[dave wilkinson]

duncan there not the usual types of cracks you see tbo. possible caused due to your cage/suspension. i'd make sure you swop your suspension over as even if you dealer is on your side. when they take pics and send them to bmw uk the coilovers may just be seen and you'll get rejected.
alot of the bmw dealers are ok with mods ect, the dealer who did mine even fitted a limiter kit before it was kds'd.

[Niel333]

[QUOTE=NZ_M3;n519020]


Neil333 - one tube is enough to do both rear mounts - If you are doing the fronts, then you need two.


Thanks for the info, its much appreciated!

[monkeycsl]

[QUOTE=Niel333;n519025]

Neil333 - one tube is enough to do both rear mounts - If you are doing the fronts, then you need two.


Thanks for the info, its much appreciated!

Im confused now if i want to do both left and right side of car will one tube of epoxy do both or do you need one for the left and one for the right.The bmw instuctions just say to pump the whole lot onto left void as they dont do the right side,just wondering as i need to do two cars and maybe pinkpanthers so dont want to order too many.:whistle:

[monkeycsl]

Ok I have prices £55 for expanding foam enough to do prob 2000 cars £145 each tube of structuring foam so two of these for one car.£345 to do one car.does any one know of alternative or opinion on asking bmw to do it free as its their problem too!:smt064

[alexk]

What is the part number guys ?

[monkeycsl]

cavity foam 83429410694 x1
structuring foam 83420307530 x2 for left and right side.
10mm plug 51711906001
Need to get these but will cost £650 to do both cars

[alexk]

cavity foam 83429410694 x1
structuring foam 83420307530 x2 for left and right side.
10mm plug 51711906001
Need to get these but will cost £650 to do both cars

Thanks.

Ι could sort a deal if more people are interested.

[monkeycsl]

Please do :notworthy: