|
|
|
|
Post Reply |
|
Thread Tools | Search this Thread |
05-15-2015, 09:04 AM | #1 |
Second Lieutenant
58
Rep 244
Posts |
Can anyone explain why the bolts that hold in the RSFBs are smaller than the holes?
Hello all. So yesterday I did the M3 rear subframe bushing swap. I rented the tool, and it went relatively smoothly with the exception of the bolts for the rear exhaust connection stripping out. No matter what I tried, I could not get those bolts to thread back into the captive nut cleanly, and one of them ended up jamming up 3/4 of the way through and snapping off rather than coming back out. I've got to try to get the captive nuts out today.
My question is actually about something else though. During this job, I noticed something rather strange. The bolts that pass through the center of the rear subframe bushings and hold them to the vehicle are much smaller than the actual holes. This is true in both cases, but the M3 rear bushings actually have an even larger hole than the original 135i parts. I don't understand why this would be. Wouldn't that allow possible slop in the entire rear end of the car? I'll post some pictures below to illustrate what I mean. Here is the original bushing with the bolt sitting in it to illustrate the size. And the M3 Bushings for comparison and finally, how the bolts from the exhaust ended up looking. I would swear thes things had damaged threads or something, they came out hard, and absoltely refused to go back in cleanly even after cleaning up both sets of threads with a tap and die set after the initial failure. |
05-15-2015, 10:06 AM | #2 |
Brigadier General
1688
Rep 3,140
Posts
Drives: 2014 M5 6MT
Join Date: Nov 2013
Location: Massachusetts
|
Drill it out and use a regular bolt and nut. Best way. I had to do it.
__________________
2014 M5 6MT
|
Appreciate
1
|
05-15-2015, 10:21 AM | #3 |
First Lieutenant
130
Rep 351
Posts |
The holes in the bushings, as far as I can estimate, are larger for ease of assembly at the factory. The entire rear suspension is loaded as a module into the rear of the vehicle.
If your concerns are alignment related I would not worry, as the forward bushings are located by alignment dowels as shown below. These two dowels squarely locate the subframe to the chassis. Photo borrowed from forum member Freon
__________________
Ohlins Road & Track Coilovers / Apex ARC 8's 245/255-35 MPSS / Wagner Downpipes / Wagner EVOII Intercooler / ER Charge Pipe / Forge DV / PowerFlex RSFB / PowerFlex Differential Bushings / MFactory 3.46 Torsion LSD / MHD Flasher
|
Appreciate
1
|
05-15-2015, 12:17 PM | #4 | |
Second Lieutenant
58
Rep 244
Posts |
Quote:
Quote:
In any case, I am noticing a marked improvement in the car, and all I have been able to do is drive it to the store and back. The wandering feeling is completely gone as far as I can tell, and it takes bumps better. A large portion or the weird secondary vibrations the car had when you hit something like a bridge seam are now gone, and it's now much more of a "one bump" type of situation, where before there was an odd reverberating feeling that was uncomfortable and annoying. |
|
Appreciate
0
|
05-15-2015, 12:38 PM | #5 |
Major General
4338
Rep 6,196
Posts |
The M3 bushings are different because the front ones are pressed in from the top, while the stock bushings were pressed in from underneath.
|
Appreciate
1
|
05-15-2015, 12:43 PM | #6 |
Brigadier General
298
Rep 4,040
Posts
Drives: 130i coupé ;)
Join Date: Nov 2011
Location: Bimmerpost
|
I wonder if aftermarket Poly or Derlin bushes reduce the hole size around the bolt
__________________
128i Sport 6MT converted to Euro 130i spec, 3.73 diff, tuned by evolve ~220 whp 207 wtq(ft-lb) SAE
In-progress: //M front arm, M3 rack, e36M lip Wishlist: Coils, n55 mnts, headers, LSD, e60 finn diff "The 1-series is the last car that BMW engineered before the Germans, as a car-making culture, fell out of love with driving." - R&T 2013 135is |
Appreciate
1
|
05-15-2015, 12:57 PM | #7 | |
Second Lieutenant
58
Rep 244
Posts |
Quote:
Even still, the job of getting them in only took about 3 hours, including time spent on the phone verifying that I did indeed have the correct parts, etc. I spent nearly as much time wrestling with those damned bolts on the exhaust, and had time left over to replace the transmission mounts and install a modified CDV. |
|
Appreciate
0
|
05-15-2015, 01:04 PM | #8 | |
First Lieutenant
130
Rep 351
Posts |
Quote:
I applaud you on how quick you got them installed.
__________________
Ohlins Road & Track Coilovers / Apex ARC 8's 245/255-35 MPSS / Wagner Downpipes / Wagner EVOII Intercooler / ER Charge Pipe / Forge DV / PowerFlex RSFB / PowerFlex Differential Bushings / MFactory 3.46 Torsion LSD / MHD Flasher
|
|
Appreciate
1
|
05-15-2015, 01:07 PM | #9 |
Major General
4338
Rep 6,196
Posts |
Funny. I had the exact same issue with one of my exhaust bolts. One of them was overtightened from the factory and the threads were all pulled when I removed it. Had to repair the threads on the center pipe and got a new exhaust bolt.
|
Appreciate
1
|
05-15-2015, 01:10 PM | #10 |
Second Lieutenant
58
Rep 244
Posts |
I have the advantage of access to a full lift, and I've done the job before on my 540i so I knew basically what to expect. the only real difference was the tool and the fact that the new ones go in from the top in front. The holes in the bushings on my 540i were exactly the same as the size of the bolts though, which is why I was a little confused.
|
Appreciate
0
|
Post Reply |
Bookmarks |
Thread Tools | Search this Thread |
|
|