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One of the four bolts joining the halves of my left front brake caliper is broken. Bizarre but there you go. I thought I was nearing the end of the to-do-list on my current project.

I pulled the caliper and removed the remaining three bolts to split the caliper. After some very careful drilling, cycling heat from an oxy-acetylene torch and cooling from compressed air, and a sharp Easy-Out, success! Managed to get the rusty broken portion out without damaging a single thread in the caliper half. That's a rare but welcome occurrence for me. Usually reaching for an Easy-out precedes by an hour looking for a new part or drilling out to the next larger bolt size.

That's the good news. The bad news is now I have to find a 9mm by 85mm bolt with a 14mm hex head (Not that it's critical. A 13mm or 15mm head would also work). To make things more difficult it's a spec 11.9 with a 1.25 thread pitch. I might be able to find 8.8 but I'm leery using in such a mission-critical application. Same for drilling out and tapping to a more common 10mm. Calipers get hot and I'm worried about differential expansion, if not immediately then over time.

I've checked with my local suppliers and The Google with no luck. Closest I've come is a manufacturer located in China. Minimum order size is 900Kg! Mr. Metric has bolts but not long enough. Fastenal has nuts but no bolts(?).

Also checked for a rebuilt caliper but no luck. Even eBay was fruitless.

Also looking for the square profile o-rings sealing the two halves. I may have luck with a local hydraulics supplier but today is Saturday.

Any ideas?

I have to look but I think I may have one laying around somewhere I can let you have.

Thanks Hefeweizen. That would be great.

I tried Mc-Master-Carr and Bolt Depot to no avail.

I looked at the parts list and there is no M9 but only M10. Please take a look and let me know
http://www.realoem.com/bmw/enUS/showpar ... Id=34_0587

Thanks Hefeweizen. The bolt I'm looking for is one of the four clamping the two halves of the caliper together. The heads are shown in the RealOEM picture as part of the complete caliper assembly but not listed separately. (Brembo calls them "pinch bolts". Unfortunately Brembo uses 8mm)

Just realized I don't have the option of drilling out to the next larger size. 10mm won't clear out the existing threads and 12mm removes an uncomfortable amount of material in a critical area.

Canadiane,

I am not so sure these guys have what you need, as they do not list the lengths, or strength.
You will have to contact them.

http://www.warrenfasteners.com/Hex_Cap_Screws.html

Best,

Just a short update, I have not been able to go into the attic of my garage yet but should be able to do that soon.

Good old Bav Auto has reman front calipers for less than $60 each with a 1-2 day lead time. It's not even worth breaking the old ones apart for that cost. I've used these previously on my 635 and the product is very good. Clean 'em, paint 'em and away you go!

Good Luck,

TGM, thanks for the BavAuto tip. Good Plan B if I can't find a bolt. Calipers were recently rebuilt and, broken bolt aside, in great condition. Your comment about breaking apart crusty calipers otherwise makes BavAuto a no-brainer.

JCS, nothing on the Warren Fasteners website so I messaged them. No response yet. Also no response from ATS "Hot Line". Thought I'd try them given they are the OEM supplier and tout their support for classics. Perhaps my Google translation into German is unintelligible.

Hefeweizen, thanks for keeping me posted. If it turns out you don't have one I now have two options. First is new caliper from BavAuto. Second is to use a 3/8" Grade 8 bolt, cut to length and thread with an M9 x 1.25 die I found at McMaster-Carr. Would need to enlarge hole in caliper to 9.35mm which is no problem. Lot's of material for that.

BTW, McMaster-Carr has an amazing selection of fasteners and website. Even has titanium, ceramic and left hand thread. Also bolts with tension indicators in the head to spot loosened bolts at a glance. Unfortunately no M9 x 1.25 x 85mm.

Bad news , was up in the attic but could not find a bolt with your description. Sorry! I keep looking though

I wonder if you can find an M10 and a 9mm die. :)

Cheers,

Ray

9mm dies are as hard to find as 9mm bolts!

hornhospital wrote: ↑Tue Jan 09, 2018 11:42 pm 9mm dies are as hard to find as 9mm bolts!

https://www.spaldingfasteners.co.uk/pro ... alogue.pdf

Thanks everyone for your input. Problem solved.

My Austrian friend is a BMW purist and calls it a hillbilly hack but here's what I did.

Got lucky and found a 9mm x 1.25 die at a local tool store.
Bought a 3/8" x 5" Grade 8 bolt.
Put the bolt in my drill press.
With the drill running, I used my 5" angle grinder with a flap disc to evenly grind the shaft of the bolt. I only needed to remove 0.35mm so it didn't take long.
Used a mill file to remove material near the underside of the bolt head where the edge of the flap wheel couldn't reach.
Polished the bolt with fine emery cloth.
Removed the bolt from the drill press and cut it to length
Threaded it with the 9mm die.

Voila! A 9mm x 1.25 x 85mm bolt. Total cost including die, $10. Best of all I didn't need to drill out the caliper and If I ever find an OEM bolt it can be easily swapped. Don't even need to remove the wheel!

Tensile strength of Grade 8 is 150,000psi. Grade 11.9 is 160,000psi. My "hillbilly hack" at a measured 9mm is 7% thicker than the OEM at a nominal 9mm but measured 8.4mm. By my calculation the strength of the replacement is, for practical purposes, identical.

BTW, in my search I learned that the head bolts from a 1500cc, 2002-2009 Honda Civic Hybrid has the same 9mm x 1.25 x 85mm dimensions. I presume, being a head bolt, it would have comparable or better tensile strength. Never went looking to find out. One unicorn hunt is enough.