+2
smaller would be not good.

 

RedAndBlackMiniS
From the looks of this it seems that this hole is less than optimal. To do this job right now I would seriously think about putting in Helicoil inserts providing you have not exceeded the correct hole size. This would entail drilling out the existing hole size to accomadate the Helicoil, tap the hole to put in the inserts, and then install the helicoils. This would end up being better than new and you could use a stock bolt. If you use the bolt and nut method you describe I believe your trailing arm has some vanes that would have to be ground off to allow a flat surface for the nut to sit on. This will still not be super expensive but would end up being done correctly.
Steve

 

I am planning on continuing to increase the size of the hole, order this part: http://www.fastenal.com/web/products...x?sku=11114441

and then put it through the hole when it fits, grind down the trailing arm a little to make it flush, and then put the nut on and call it a day. Are you all saying this isn't the best option?

 

Could someone point me in the right direction for what helicoil set I would use in case I went that route?

 

If the helicoil is of a tube with threads inside and out, it will probably work well. Stay away from the wound spring type that are sometimes used to repair spark plug holes. Helicoil is a brand name that you should be able to look up.

As for the bolt you selected, as long as it is the same diameter and thread pitch that should also work and you will be able to use the factory torque setting. Use washers under the head and nut and use a nylock nut.

Whichever you go with, I would plan on taking it apart maybe monthly to check that it is not failing.

 

RedandBlackMiniS,

Reading this thread I really feel your pain. I think the best route would be to purchase a new trailing arm for $380, but unfortunately I know you are trying to avoid that expense. Have you tried calling some local salvage yards or shops? Someone may have a used trailing arm they could sell you? The actual trailing arm isn't something that should have wear, so used should be as good as new.

I have been in your situation, ...when I was in high school, I and some buddies put a header on an old Ford Capri I owned. Problem was that we bolted American threaded bolts into a European Capri that had European recieving threads. ...needless to say I had about 8 screws that were a royal PITA to remove. I had to eventually bring it to a shop and pay big money, I think it was about $800 (this was in about '86 or '87) to get all the bolts out and everything re-threaded correctly. To this day I remember that nightmare.

You'll probably remember this one too!!
One way or another this will work out, ...if you can get the funds together purchase a new trailing arm for 100% piece of mind.

 

If you want to go with helicoil, consider using timesert as well.

Remember only one bolt holds that entire suspension and if it snaps going around a bend, you and your car can be history. I was that close so I am now cautious.

Buy a new trailing arm.

 

..I did a quick search on eBay, looks like there are a ton of used trailing arms for the earlier R53 models (doesn't help you I know), but they are all around $75-$100.
This led me to some online used car part sites,
check this one out, they look like they have the part for your 2010 S, yet you need to put your phone number and email address in to get the price.

http://www.uneedapart.com/

I am guessing you can find this part for around $100-$200 used ..and for a part that doesn't have any mechanical/electrical or bearings,etc ..it should be good.

Sucks, but I'd get a new/used trailing arm.

 

The new trailing arm bolt hole is not threaded when factory new. It will self thread when you first Install the factory bolt. When you reinstall the bolt, you have to really careful not to cross thread or weaken the threads.

There is no nut used in the OEM setup.

 

I appreciate everyone's words... really helpful to me, you have no idea!!

I think I've done all I can do... not seeing much progress now and I don't enjoy wasting all day (5 hours a day of just drilling) doing something like this.

So- I decided I would call around to some junkyards and found a place in California that is willing to sell me a used trailing arm for $175... is this a good price, or should I keep searching around?

Seriously, thanks again for the words and the help, you guys are great!

 

not sure if that is a good price, it is about 1/2 of a new one though.

So, just to be sure that a used one will work, Slinger88 mentioned that a new arm is not threaded when new. Will a used one still work like new? ...will a bolt coming out of a used one and then the bolt from RedBlackMini's cooper still seat/seal correctly on the used trailing arm? -you wouldn't want the bolt to back back out if the threading was too loose?

 

Op, good luck to you and hope you find the right solution for your problem. Do tell us what you did.

 

RedAndBlackMiniS
Check out this thread and post #28. You may want to contact this person to see what he has used in the past.

http://www.*********************/for...#axzz2334UUdxR

Good luck, Steve

Edit: It looks as if they will not allow this link. Go to Motoring alliance and do a search for trailing arm and it will come up.

 

He went with a bigger/longer bolt because he got the original out w/o too much damage. His problem was clunking, not a broken bolt. But he did investigate the cost of a new trailing arm.

 

Ended up canceling my order from original scrapyard I went with, and ordered from another seller who included the hub w/ the trailing arm for the same price shipped... I didn't want to have to take the hub off and I needed to replace it as I had a stripped lug hole anyways. So win-win.

 

Dude I wish you would of shot me a PM. I would have tired to help out

I think getting a new arm is the way to go. Make sure you use some Anti-seize before installing bolts in those arms.

 

slinger688
I am not exactly sure what you are refering to here. On Motoring Alliance there is a thread (NAM whould not allow the link)on a broken bolt in the trailing arm. There is some good info in there. One of the posts references putting in Helicoils on his race car because the alluminum trailing arm can only withstand one or two removal/reinstalls without failing. This is understandable because the stock bolt is a self tap design. This would seem to be the logical fix to me.
Steve

 

The person to pm on Post 29 on this thread.

 

slinger688
The post that I refered to was #28 and the poster was "octane". This is on the Motoring Alliance forum under "trailing arm broken bolt".
I refered to this useage of helicoils because it may be the best way to correct this problem, especially if you may need to remove your rear shocks for adjusting such as the Koni yellows. Because they are using a self tapping bolt, and such high torque in this area it a failure waiting to happen in an alluminum trailing arm. This is a much cheaper fix than a new arm and will be better suited if you have to remove and replace your rear shocks several times.
Steve

 

Ok, thought you were referring to this post. I saw those posts on alliance on helicoils. Probably more difficult here because the trailing arm looks pretty mangled here.

 

Update. Been working the past couple days a little at a time and have finally managed to drill it all out (enough for the bolt to fit at least).

Here is why I ended up doing this. I am going back to college is less than a week. I was calling around places to see if they had trailing arm, most did, so I ordered from a guy. He ended up calling me 2 days later saying that the trailing arm wasn't in stock. Refunded money. Called all those places that had it in stock again and none of them had it in stock like they said they did! I got tired of it all, and just decided to go at it. Took the trailing arm off so I could work in the house, and drilled and drilled and drilled. It was the most tedious thing I have EVER done, but it needed to get done because I needed my car for college. I bought an angle grinder and the new bolt (with the nut) is on its way. Hopefully it gets here very soon so I can put everything back where it needs to go and get the car driving.

Here are some pictures:





I'll let you all know how it turns out.

 

Took my angle grinder to it and this is what I have so far. I need to wait until I have my new bolt/nut in but I took one I had laying around and the nut sits flush on the trailing arm.

 

The word is getting out:
https://www.northamericanmotoring.co...rs-beware.html

good luck with yours!