subframe fixes

[monkeycsl]

Hi what do you guys suggest to stop subframe cracks ie powerflex subframe bushes which are larger diameter to spread the load better and the resin injected into the chassis void to stiffen it up.Has anybody done this,pros and cons and costs would be handy.cheers worried because goodwill will be finishing at 10 yrs so not long and i have two to worry about now.Also has anybody had the strengthening kit fitted and what was the cost.

[NZ_M3]

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.

[monkeycsl]

Will be getting the resin injected into my crack then pardon the pun.the bmw bushes have. A raised lip which puts pressure on a small area but the power flex ones are flat so they must help.

[s.mac]

Any links on how to do this Tom?? Sounds like its worth doing

[pinkpanther008]

Monkey, did i hear you say 'two' now thats just greddy! You had yourself some twins or did you chuck in the heavey 32 and got another M-car?

Let me know of any joy you have with the epoxy resin lead?

PP

[Rager54]

Originally Posted by monkeycsl

Will be getting the resin injected into my crack then pardon the pun.the bmw bushes have. A raised lip which puts pressure on a small area but the power flex ones are flat so they must help.

Does anyone know where I can get this done? (No gay jokes please)

[monkeycsl]

http://forum.e46fanatics.com/showthread.php?t=710760 check this link out.Yes pink panther i am greedy and need two sg m3's in my life.R32 for sale so have 3 thirsty mouths to feed and a little one named jessica too.

[s.mac]

Cheers

[NZ_M3]

Originally Posted by monkeycsl

Will be getting the resin injected into my crack then pardon the pun.the bmw bushes have. A raised lip which puts pressure on a small area but the power flex ones are flat so they must help.

If you look at online photos of cracks and really significant failures you will see that the cracks usually develop around the actual bush mounting - often when it tears it also tears an area larger than weld in plates out. The worst one I've seen with welded plates in was on a car where rust proofing failed and it basically dropped the whole floor out of the car - very nasty.

Bear in mind that the subframe bushings are there to act as a damper, so by enlarging the foot print area and going to a harder bushing you are transfering a higher load into the floor, thus eliminating any benefits you might gain out of the larger foot print (if it even helps at all)

Originally Posted by s.mac

Any links on how to do this Tom?? Sounds like its worth doing

Monkeycsl beat me to it ....

Few things to remember about this fix :

1. it is the 'official' BMW recommended repair if the floor cracks are less than 25mm (basically they drill out the end of the crack to stop it spreading, weld the crack itself, and then inject this epoxy).

2. If the floor is replaced by BMW, the secondary repair requires that this epoxy be injected to prevent future tear (I've taken this as to mean that it is considered a secondary preventative fix designed by BMW to prevent this from happening in the future).

3. The epoxy is only injected into the rear two mounting spots - if you want to you can also do the front two mounting points - these can be accessed via the rear seat belt belt clip bolt holes - just make sure you don't squirt too much in those thus making it impossible to reinstall your seatbelt belt clips. Personally I only did the rear two mounting points as this is considered sufficient by BMW.

For the cost of the epoxy and foam, I am of the opinion that it is a worth while preventative maintenance to do on the car - and you don't run into rust issues in the future. It also looks very original after the injection (you are only drilling one hole in the middle of the floor ridge afterall - and a plastic bung is provided with the kit to seal this to make it look factory).

NB - very important to not move the car for at least 24 hours after you've injected the stuff ... leave it for two days if the weather is warm.

[Niel333]

I also need to do this to my car, its got a crack bigger than 25mm but replacing a boot floor in SA is not really an option. I have ordered the turnermotorsport kit and the cavity foam, but my local dealership cant get the structuring foam no 83 420 307 530.... is there a replacement that I can use?