I bought a 5/8" fine thread bolt at a hardware store, and a tap to match. The tap started straight and true in the stripped hole. I then opened up the bottom hole in the shock slightly. It seems like a real hack job the way that I describe it, but it worked out clean. Like one of the postings state, the force is transmitted through the tapered interface between the shock and trailing arm, the bolt is just to keep them together.

My mistake was putting anti-seize on the bolts and then torquing. The torque number is for a dry fit. 120 ft lb is a hell of a lot in cast aluminum.

Mike

 

This is a very good post. I'm taking out my rear coilovers to make some rebound adjustments this winter while its in storage, and this will be the fourth time I have removed that bolt. I have a feeling it's not going to torque to spec when everything is back together. I'm also boring a small hole in my interior to adjust the rebound setting of the KW V2s now. I can't imagine the OH ***** feeling for those that stripped these threads on their daily drivers.

 

Its interesting that I was thinking of this again. I picked up a set of Koni Yellows, and I'm thinking of going away from my 5/8-18 bolt solution that I listed above. The one disadvantage is that the 5/8 bolt is slightly larger than the hole in the bottom of the stock shocks, so those holes had to be reamed slightly (14mm is about .56 inches, 5/8 is .625). By putting a metric 14mm bolt through backwards (head toward the wheel), then you never have to thread into the aluminum again. I'm thinking that is a significant advantage, and is worth grinding a flat spot (or making a tapered washer) for the bolt head against the control arm.

Mike

 

Sorry I didn't take any pictures since this is an old thread, but I figured I'd report in. I've driven about 40,000 miles with the helicoils in place and haven't had any issues! Hope everyone is having the same luck!!

 

When removing my rear shocks I am thinking of replacing the self tapping three lobe bolt with a standard design to help eliminate the possibility of stripping the thread.
Any opinions on this thought? What grade bolt and material would be suitable for this application?
Thanks, Steve

 

Not to answer a question with a question, but what grade bolt is the tri-lobular one that you're removing? Reason I ask, is that you would more than likely want some ductility based on the forces involved. The bolt you're removing (if it is what I think it is), is case hardened. If you go up higher, you may get some strength, but add some brittleness.

Just my 2 cents.

 

Grinch
I was trying not to crawl under the car in the cold garage but you peaked my interest. The lower shock bolt is a grade 10.9 and looks to be plated (probably zink?).
Steve

 

There have been a couple of good posts on here on using a guide to help alignment when drilling and tapping. I have not dissasembled mine yet to see how the spacer fits into the trailing arm but I had a thought about making a guide depending on how the two mate together.
Instead of sacraficing one of your rear shocks one could purchase a set of these shock spacers for $20.
http://www.waymotorworks.com/wmw-rea...k-spacers.html
You could then put it into a drill press and enlarge the hole for the correct size to be drilled for the helicoil. The second one could be drilled and tapped so you have a guide for the tap as well. As long as these spacers could be clamped to the trailing arm to line up it should work well. This would all depend on how the two pieces mate. Anyone who has had this apart care to chime in?
Steve

 

Definitely zinc plated, probably mechanical plating for corrosion resistance. I wouldn't go any higher on grade than 10.9.

 

Can anybody speak to the reasons or mistakes that have been made to cause these to strip? It sounds like a problem that does not happen very much and I have talked with individuals who replace hundreds of customers shocks and stated he has never had this problem.

I am just curious as to what to look out for and be careful with since I am removing my shocks for a second time soon to put the JCW suspension on. First time was for just a rear swaybar install.

 

Mine stripped on the second install, first was for a swaybar, second was to install springs. My car is an 08, and I'm sure that corrosion played a bit of a part as well.

Mike

 

Well, hopefully on a 2012 I won't have the issue... Would it help to support the trailing arm and leave the top mount bolted in while removing and re-installing the strut?

 

Some guys think it is easier to start the bolt in straight with the top mount not installed. I have installed the top first, but either way, make sure that you get the bolt started straight.

Mike

 

ditto, i have just recently heard of this problem... i was planning to swap back and forth between suspension for winter and summer, but maybe that's not such a good idea now.. can someone confirm if this is still the case for 2013's (don't see why it wouldn't be).

also, pics?

 

I think that the issue comes when you try and torque the fastener to the recommended value (105 ft lb, if I remember). The bolt is self locking (not perfectly round), and this can dig into the aluminum of the trailing arm. Repeated removal and reassembly can damage the threads, which then fail when applying the heavy torque.

Mike

 

I'm resurecting this thread as I just went through a "fix" because the shop that did a preemptive fix I had them do, drilled the hole too large for the steel insert that they put in and it came out when I removed the bolt to replace the shock.

Now, the insert that they put in the other side is just fine. These are called "time-serts".

Because the hole was already over sized, I only needed to grind away a bit of the trailing arm. For this I used a 1" hole saw. To keep the hole saw centered I fit some plastic tube together to make a 1/4""x5/8" bushing. Then I used a Dremal to smooth things out. I also used that hole saw to cut a washer out of 1/4" steel plate. The bolt I used was a 9/16" grade 8 5" long course thread bolt and a lock nut. It all went together nicely and torqued it to 90ft-lbs. there is now reason to go higher than this. If the wheels on the the Gen I are torqued to this and that is good enough for them, it is good enough for this.

If any one needs a bolt for this, I have extra that I will sell. I also have a Time-sert kit that I will sell or rent. Just PM me.

 

re bumping this - looking to run it "stock" for as long as possible. I think I will be soon looking at the 3rd time for removing and reinstalling these, I have been using antiseize day one on it, not sure whether that has helped or not. Has held fine so far, and been very careful not to overtighten. I've probably undertightened it every time I've put it in

 

Kyoo
I had the rear shocks in and out of my first MINI a bunch of times and never had any problems. I believe that using the never seize helped, as did being really careful with hand threading in the bolt and not over torquing it. By "not over torquing" I mean I never went above about 100 ft-lbs and was probably a bit less.

Something for you to think about is to replace the self tapping bolt with a regular 14-1.5x100 grade 10.3 (I think the grade is something like that) bolt and a bit of never seize.

 

The proper torque spec of a fastener is based on the fastener size and material. If it is not torqued properly then it could come loose.

A 9/16 grade 8 course threaded bolt should be torque to 115 ft-lbs.

 

There are a lot of factors that go into a "required bolt torque" including the desired clamping force as well as the the expected coefficient of friction, shear strength of the threads and strength of the shank. The value quoted appears to be the max value the bolt can take and not necessarily a value to keep it from loosening; hence Locktight. Case in point, the 14mm wheel bolts are factory spec'ed at 102 ft-lbs.

If this were high strength steel on high strength steel, 115 ft-lbs would likely be fine. The problem is, this bolted joint is not designed to be disassemble and reassembled. And BMW has not given a reasonably well engineered solution for this. It is high strength steel on much weaker aluminum with poorly made threads, which this will have having been cut with a self threaded bolt. In this case the appropriateness of any selected torque value is at best a guess.

If loosening is of concern, then the torque should be checked periodically. In any case "over torquing" has been shown to strip the threads in this case.

 

I was referring to your modified setup which I understand to consist of a grade 8, 9/16" course thread bolt and nut installed in a clearance hole in the trailing arm. This I would torque to the 115 ft-lbs typical for that type of fastener.

The OEM setup is a joke. I don't even know where to begin.

 

I missed the connection to my post. Kind of a duh moment on my part.

You are right, with that I could go higher. I have checked the torque on it and raised it to 100 ft-lbs, which is where I have the other side torqued to. With the insert installed on that side I am uncomfortable going higher. So I am keeping both sides the same and will be checking them periodically.

 

TIP....
Here is a tip for anyone Who has removed the trailing arm bolt to change shock/springs/coilovers and you DON'T want to strip the threads.
#1 NEVER, I SAY NEVER use an impact gun!!!
#2 Thread by hand
#3 patience!

When putting the lower bolt into the trailing arm, leave the two UPPER bolts on the coil/shock assembly loose, say like 3/4 of an inch from the end of its travel.

Use a jack to raise the trailing arm close to the lower shock mount.
Slowly work the bolt through the lower shock mount and into the trailing arm.
The loosened shock assembly will give you the ability to move the shock around and slowly work the bolt into the hole properly. If the two uppers are tight, YOU WILL cross thread it if it is off even slightly.
You should be able to thread it by hand 90% of the way. Once you get it snug by hand then Use a ratchet to snug it tight, don't torque it yet.
Then tighten the upper bolts and tourque them.
Then tourque the lower bolt
NEVER use an impact gun for this.
You will need patience as it is tough to get it lined up properly
Back the bolt out if you feel too much resistance.
You should feel it thread, then It gets tight, thread, then tight, thread, then tight.

If it's already stripped, sorry, at least you have some good support to get it fixed. Hopefully this will help anyone else BEFORE it happens.

 

^ good advice there. For me, I've been using antiseize on my threads and have never had an issue with it lining up 100% perfectly. fits directly in, I gently turn it on with 0 resistance, and do not use a torque wrench. I just get it to 'eh, that's tight enough' and leave it alone. not a strong guy by any means

 

It's OK to torque it to the 103ft/lbs . If you have threaded it lightly and it went in 90%, then ratchet it until snug, then tourque it.

If you have to force it in, you got problems!