Rear Sub-frame Bushing replacement job questions.

[feeshta]

Hello all. So I bought a 2012 135i CPO a few weeks ago, and it has one relatively annoying issue that I'm hoping is due to the poorly designed factory rear sub-frame bushings. It has a weird clunking sensation once warmed up. I have read lots of info on how bad they are in this car, and I agree that the rear end has a distinct squirmy and unpredictable feel about it, so I already went and ordered the M3 rear sub-frame bushings for the car. They are currently sitting on the shelf waiting for the installation tool to arrive, as I have to wait for that to be available.

I'm also thinking of replacing the brake lines with an ECS stainless set while I am at it. I will apparently need to remove the rear brake lines in order to lower the rear sub-frame enough to get to the bushings anyway, so it seemed like a good idea to me.

Does anyone who has done this job or simply replaced the brake lines have any opinions on whether that is a good idea and worth the time?

I did the same job on my 540i in the past, but you did not need to remove the brake lines on that car, as they were plenty long to give you enough play. I will be using a lift and a hydraulic transmission jack to do the job, so I'm pretty sorted on that front. The only problem I had last time was the bushing press tool snapping in two, but hopefully that was a freak occurrence.

So, anyone have any insight to offer?

[tracer bullet]

I'm doubting any normal person, or anyone at all, would notice SS braided rear brake lines. Aside from the factory lines likely being quite good, a lesser % of braking is done in the rear to start with. If you have them already, maybe why not go for it. But I don't think it would be high on may folk's lists.

You might be interested to look around for a thread in this area from a user going very in depth to the different options each company has and how they fit, just for curiosity.

If you do it, you may already know to be darn sure to use the right wrench(es), they are in my experience very soft and easy to strip.

[feeshta]

Originally Posted by tracer bullet

I'm doubting any normal person, or anyone at all, would notice SS braided rear brake lines. Aside from the factory lines likely being quite good, a lesser % of braking is done in the rear to start with. If you have them already, maybe why not go for it. But I don't think it would be high on may folk's lists.

You might be interested to look around for a thread in this area from a user going very in depth to the different options each company has and how they fit, just for curiosity.

If you do it, you may already know to be darn sure to use the right wrench(es), they are in my experience very soft and easy to strip.

I was actually thinking of doing the whole set of 6, rather than just the rears. ECS has all 6 for $129, which is a pretty decent deal. The rears only seemed like a half-arsed solution to me, as you would still have expansion in the other lines affecting pedal feel. Since I am going to have to bleed the brakes anyway, it seemed like a good time to do this.

Stainless lines did make a noticeable improvement on my 540i, but that car had 145K on it when I made the swap and the factory lines might have been pretty whooped. I had major problems getting the old lines off the car in that case though, as the factory hardware was extremely corroded and I actually ended up having to replace the rear steel brake lines because the connections were impossible to get apart without breaking them. That is part of what made me think of doing this now, as the job would likely be much easier now than later, and stainless lines are supposed to last nearly forever.

[fe1rx]

Originally Posted by feeshta

So, anyone have any insight to offer?

I suggest doing some searching regarding brake hoses.

http://www.1addicts.com/forums/showthread.php?t=1083544

http://www.1addicts.com/forums/showthread.php?t=1090379

http://www.1addicts.com/forums/showthread.php?t=1093684

I am happy with the Techna-Fit lines, and there are others that use the correct female end fittings. I can't recommend any line that doesn't have the correct female end fitting. There really is no compelling reason to change the lines from OE, unless they are damaged or have reached some arbitrary age limit. Since your car is only a 2012, if they are undamaged, I wouldn't change them.

[Fume]

I haven't gotten a chance to have a good look at the amount of clearance there is around the subframe so maybe this is an obvious question but is it necessary to take off the exhaust system to get enough room to get the (front set) rear subframe bushings in? If I use the HPA tool and go with M3 bushings, which go in from the top, it seems like I would need a ton of clearance to fit the bushing and the ring on top of the bushing.

[feeshta]

Originally Posted by fe1rx

I suggest doing some searching regarding brake hoses.

http://www.1addicts.com/forums/showthread.php?t=1083544

http://www.1addicts.com/forums/showthread.php?t=1090379

http://www.1addicts.com/forums/showthread.php?t=1093684

I am happy with the Techna-Fit lines, and there are others that use the correct female end fittings. I can't recommend any line that doesn't have the correct female end fitting. There really is no compelling reason to change the lines from OE, unless they are damaged or have reached some arbitrary age limit. Since your car is only a 2012, if they are undamaged, I wouldn't change them.

Thanks for the info, Fe1rx. Personally the main reason for my consideration of this is the issues I had with replacing the rear brake lines on my old 540i, and a desire to avoid such issues down the road with this car. In that case, the connections from the rear soft brake lines to the hard lines was completely fused by corrosion, and it was impossible to get them apart, even with heat, breakfree, etc. The metal had decomposed to the point that it was too soft, and simply rounded off, even with the proper tools.

I guess I could also take the approach of being more proactive with maintenance of these areas. Since I am getting into the car a lot earlier in it's life than the 540i which had 85K miles on it when I bought it, I might be able to keep corrosion from ever reaching that level.

One other quick question for you Sir if you have a moment. I am also considering doing the M3 control arms front and rear, but I had a question about alignment after installation. I know for sure that the front control arms require an alignment after installation, due to the fact that they change the geometry, but I have not been able to find whether or not that is also true of the rear arms. My thinking here revolves around maximizing my productivity. I do my work at a military Automotive Hobby Shop, which means I am limited to a maximum of 8 hours in any given day, and I have to pay for the time. I was thinking that the M3 rear Sub-frame bushings and rear control arms might make for a nice full day at the shop. When I did the RFSBs on my 540i, it took about 3 hours to complete the job. It took about 2 hours or so to do the rear control arms on that car, so it seems like I could knock out both in one day.

I know that when I finally get the chance to do the coilover system, I will need to realign the car, so I was thinking for sure that the front control arms job should be done at the same time, but I was wondering whether it made sense to split up the front and rear control arm jobs or not. Obviously if the installation of the rear arms requires an alignment, it would be easier to do control arms all around at the same time as I do the coilover install, I'm just not sure I can fit that all into one day, as coilovers took about 4 hours on the 540i, and it would be cutting it close to add both control arms jobs to that.

Originally Posted by Fume

I haven't gotten a chance to have a good look at the amount of clearance there is around the subframe so maybe this is an obvious question but is it necessary to take off the exhaust system to get enough room to get the (front set) rear subframe bushings in? If I use the HPA tool and go with M3 bushings, which go in from the top, it seems like I would need a ton of clearance to fit the bushing and the ring on top of the bushing.

I don't remember seeing mention of removing the exhaust in the DIY that is posted somewhere around here, although I'll be darned if I can find it right now. On my 540i, you could simply disconnect the rear exhaust hangers and let the system hang a little. I used a floor jack to hold it up and keep it from hanging on the front connections, but you could probably use some string or a bungee as well. Not 100% sure that the same is true with the 1er, but I'm guessing it might be close.

[feeshta]

Originally Posted by Fume

I haven't gotten a chance to have a good look at the amount of clearance there is around the subframe so maybe this is an obvious question but is it necessary to take off the exhaust system to get enough room to get the (front set) rear subframe bushings in? If I use the HPA tool and go with M3 bushings, which go in from the top, it seems like I would need a ton of clearance to fit the bushing and the ring on top of the bushing.

Found that DIY finally. couldn't find it with an internal search for some reason, but google turned it right up. There is no mention of needing to remove the exhaust, so it seems that should not be a problem.

http://www.1addicts.com/forums/showthread.php?t=671569

[fe1rx]

Originally Posted by feeshta

Thanks for the info, Fe1rx.

One other quick question for you Sir if you have a moment. I am also considering doing the M3 control arms front and rear, but I had a question about alignment after installation.

I don't remember seeing mention of removing the exhaust in the DIY that is posted somewhere around here, although I'll be darned if I can find it right now.

You are welcome.

If you change any of the control arms front or rear you need to do an alignment.

I can confirm that I did not need to remove my exhaust to change the RSFBs.