Front Caliper Carrier Bolts
 

So I went to do my front brakes a few weeks ago and for the life of me, couldn't get the caliper carrier bolts off. I tried some heat, lots of penetrating fluid, breaker bar, impact gun...split a Craftsman 16mm socket in the process, and eventually gave up. The one bolt I was working on actually started to round off just a bit, so I went ahead and ordered some replacement bolts just in case...part number 34116767217 (via RealOEM).

I'm going to take another stab at it tomorrow, but just realized that the new bolts are actually 18mm, not 16. Part number on the package is correct. Did they change at some point? Did I get the wrong bolts? RealOEM doesn't list the head size. Measurements do seem to be correct (M12-1.5x41). I just don't want to pull everything apart, possibly destroying the current bolts that are in there, only to find out I have the wrong bolts. I don't have a bolt to compare to since I have yet to get them out. Any input anyone has on this would be greatly appreciated. Thanks!

heat the bolt to break the loctite down (and any corrosion).

Sure you're loosening them and not tightening them? Since most people loosen them facing from the front of the hub and not the back of the hub, the old saying of righty tighty, left loosey is wrong. If you face the hub you will be spinning the breaker bar clockwise.

Definitely loosening them. Those buggers are ON THERE. Going to try more heat and a longer breaker bar today. Yes, I'm replacing the rotors as well.

This still doesn't really address my concern over the change in head size for the bolts. I guess if the specs measure out like they're supposed to, and they do, I won't worry too much about it.

Make sure you use only a 6 point sockets. As long as the bolts are the same length, hardness, thread and diameter it shouldn't matter.
If you are concerned drop by BMW dealer and check with them.

Update: Yesterday I went to do the brakes again, this time starting with the passenger side, which I didn't try last time before I got discouraged. Both carrier bolts came right off with a quick zip from the impact gun, and FWIW, the new bolts with the 18mm head were a direct fit. Exactly the same as the 16mm bolt I pulled out, other than the change in head size. Had the passenger side pads and rotors changed out in a half hour. Back over to the driver's side...

Bottom carrier bolt came out using a breaker bar and a 4ft pipe on the end...but that top one is fudged, for sure. Tried breaker bar and pipe, but 6pt 16mm impact socket just slips off eventually as the head was slightly rounded off when I tried to get it off the first time. Tried heating it (I only have a MAP gas torch), no luck. Went at it with the impact and that sucker didn't budge. Now the head is fairly rounded off and the impact socket is even slightly damaged (still usable, but noticeably damaged).

Anyone have any other ideas how I can get this damn bolt out? I thought about grinding off the head, but it's actually threaded into the caliper carrier itself, which is in between the bearing carrier and the rotor, so I'd still have to figure out how to back the bolt out of the caliper carrier in order to remove it. If the head wasn't rounded, I could maybe get it with the breaker bar/4ft pipe combination (only tried the breaker bar last time, before the bolt head started to round), so I'm thinking of trying one of those turbo sockets to see if I can break it loose with the pipe. I'm certainly open to any other ideas.

Try something like the "Bolt-Grip" socket sets... Amazon.com: Irwin Industrial Tools 54019 Metric Bolt Extractor Set, 9-Piece: Home Improvement

I've used these with success. I would use a 1/2 drive with a pipe as well

Or dremel the bolt head off.