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Discussion Starter #1
For those desperate with the two M8 bolts holding the disk to the final drive as I was, the two cobalt drill bits in the image will do the work fairly easy.

The worse nightmare: you want to replace the rear brake disk and have removed the rear wheel, now you want to remove the two M8 countersunk 5mm-hex bolts holding the rotor with the rear drive together. As the repair manual tells you, you heat the bolt well above 100C/212F to melt the Loctite thread lock, then you put in a 5mm hex and because some idiot before used an impact drive on them, no matter how careful and how good the quality of your 5mm hex is, the damn thing doesn't come out. The hex gets rounded, the hex key starts to slip. Then you try to knock in a larger torx (T35), yank on it, and break it (like I did). You ponder whether to use one of those screw removal kits from Amazon/TV, whatever. Stop right there.

After giving it a better thought, I decided to drill into the bolts. The attached image has all information you need if you're in the same situation. The drill machine I used is the M18 Hole Hawg Right Angle Drill from Milwaukee with the top handle removed. When fastening the drill bits in the chuck, push them all the way in, ignore the triangular profile on them. They may wobble a bit, but you're holding the machine in the hand anyway. Most important, the setup fits between the exhaust and the disk. Clean all grease from the bolts if any.
Start with the 3/16" cobalt drill bit and drill into the hex hole about 8mm / 5/16" deep. Then use the 5/16" cobalt drill bit and drill slowly until the crown/head of the bolt comes off. Use enough pressure on the drill and go easy. Both bolt crowns/heads can be remove like that. The disk can now be removed.
After that, use the torch to heat up the stubs one at a time using a new pair of channellock pliers 10"-12" long, grab the stubs with the side and NOT the tip of the channellock(!) right next to the rotor, apply all the power possible (w/o the channellock slipping) and start spinning counter-clockwise. The stubs will start rotating. Eventually the stubs will come out.
Try not to drill too deep with the 3/16" bit, so the stub has enough meat to not fold under the channellock pressure.
That's how I resolved my 2005 LT's "cowbell".
Good luck!
 

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Wrencher Extraordinaire
2005 K1200LT
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It is really silly that BMW put encapsulated thread locker on those bolts and only a 5 mm Allen. I have had to use a cold chisel on them and drilled them a few times over the years on many bikes I have worked on. They really only serve the purpose of holding the disc in place when the wheel is removed and did not need to be that "stuck" on.
 

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Discussion Starter #3
I know. Is a sobering experience when you encounter those two bolts. I thought I want to kick a butt for that. The abs ring went off easier.
 

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Good Job !, and that is a nice drill motor you got :wave
 

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One of mine was stubborn. Even with heat I rounded out the hex. Cut a slit in the head and used a impact flat drive bit and it came right out.
 

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Discussion Starter #6
One of mine was stubborn. Even with heat I rounded out the hex. Cut a slit in the head and used a impact flat drive bit and it came right out.
Glad to hear. The two bolts can be really nasty. I broke a T35 torx in one no matter how much heat I used on it.
 

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Discussion Starter #7
Good Job !, and that is a nice drill motor you got :wave
Thanks! Totally recommend this procedure if anything else fails. It saves the final drive parts and even the old disc didn't get any damage. But most important, it works if nothing else worked.
After that, one has to really heat up that ABS cog ring (well above 200C/390F) to get it to move even a bit. Freezing the new disk (I used a nice EBC) and heating the ring properly above said temp makes the ring slide on the new disk effortlessly.
 

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For those desperate with the two M8 bolts holding the disk to the final drive as I was, the two cobalt drill bits in the image will do the work fairly easy.

The worse nightmare: you want to replace the rear brake disk and have removed the rear wheel, now you want to remove the two M8 countersunk 5mm-hex bolts holding the rotor with the rear drive together. As the repair manual tells you, you heat the bolt well above 100C/212F to melt the Loctite thread lock, then you put in a 5mm hex and because some idiot before used an impact drive on them, no matter how careful and how good the quality of your 5mm hex is, the damn thing doesn't come out. The hex gets rounded, the hex key starts to slip. Then you try to knock in a larger torx (T35), yank on it, and break it (like I did). You ponder whether to use one of those screw removal kits from Amazon/TV, whatever. Stop right there.

After giving it a better thought, I decided to drill into the bolts. The attached image has all information you need if you're in the same situation. The drill machine I used is the M18 Hole Hawg Right Angle Drill from Milwaukee with the top handle removed. When fastening the drill bits in the chuck, push them all the way in, ignore the triangular profile on them. They may wobble a bit, but you're holding the machine in the hand anyway. Most important, the setup fits between the exhaust and the disk. Clean all grease from the bolts if any.
Start with the 3/16" cobalt drill bit and drill into the hex hole about 8mm / 5/16" deep. Then use the 5/16" cobalt drill bit and drill slowly until the crown/head of the bolt comes off. Use enough pressure on the drill and go easy. Both bolt crowns/heads can be remove like that. The disk can now be removed.
After that, use the torch to heat up the stubs one at a time using a new pair of channellock pliers 10"-12" long, grab the stubs with the side and NOT the tip of the channellock(!) right next to the rotor, apply all the power possible (w/o the channellock slipping) and start spinning counter-clockwise. The stubs will start rotating. Eventually the stubs will come out.
Try not to drill too deep with the 3/16" bit, so the stub has enough meat to not fold under the channellock pressure.
That's how I resolved my 2005 LT's "cowbell".
Good luck!
BMW is a big fan of red thread locker. 212F doesn’t make a dent in that stuff. You need to be closer to the 500F that Loctite states. When I replaced my rear disk, I heated those bolts up to over 400F and the screws came out pretty easily. Anything less than 400F and you will struggle.

Loctite Threadlocker Red 271 from Loctite Adhesives
 
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Discussion Starter #9
BMW is a big fan of red thread locker. 212F doesn’t make a dent in that stuff. You need to be closer to the 500F that Loctite states. When I replaced my rear disk, I heated those bolts up to over 400F and the screws came out pretty easily. Anything less than 400F and you will struggle.
In the repair manual they specify Loctite 243 for the front brake disk to wheel "(clean thread + Loctite 243)" and (interestingly) none for the rear wheel: "Brake disc to rear wheel drive (clean thread + new screws)......................... 21 Nm" although the previous paragraph instructs that "Screws are secured with thread-locking compound. Heat the screws (arrows) securing the brake disc to approx. 100 °C (212 °F) to remove and remove the brake disc."
(page 34.9)

The new OEM screws ordered came with blue Loctite on them which is 242 or 243 (both blue, and removable). Kill me if I know what the heck they concocted here, maybe they missed to specify the thread lock in the manual, maybe they knew the OEM screws come with Loctite on them, but knowing what I know about German and Austrian mechanics, they are paranoid about screws that hold two important things together and will add Loctite on top of Loctite and tie them with a zip-tie if they can then cast everything in carbonite and coat it with diamond if possible just to make sure. Have a good friend of that particular tribe that used to drive me crazy everytime he would add a few more zip-ties on something that I already zip-tied like more than perfectly. He was never satisfied. Once I measured the distances between zip-ties on a cable tree and placed them equidistantly even around corners at specified distance, he came and instinctively added a few more zip-ties. That's how they are. :-D
 

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So tie me to a tree if I'm just not getting why the heck(ll) we need locktite on these two screws in the first place since the wheel studs are doing the trick of holding things together. Now if the studs, heaven forbid, should come loose and you see your rear wheel rolling down the road ahead of you, well then I wish I would have put locktite on those screws so I could protect the disc from coming off as well.
 
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I've drilled many of the tapered heads off & then removed the threaded stud with vice grips. I just lightly hand tighten the bolts with a 5mm hex t-handle.
 

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So tie me to a tree if I'm just not getting why the heck(ll) we need locktite on these two screws in the first place since the wheel studs are doing the trick of holding things together. Now if the studs, heaven forbid, should come loose and you see your rear wheel rolling down the road ahead of you, well then I wish I would have put locktite on those screws so I could protect the disc from coming off as well.
Yep, Bavarian engineers know that skating on the rear brake disk is safer with those two screws held in place by Loctite.
 

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So tie me to a tree if I'm just not getting why the heck(ll) we need locktite on these two screws in the first place since the wheel studs are doing the trick of holding things together. Now if the studs, heaven forbid, should come loose and you see your rear wheel rolling down the road ahead of you, well then I wish I would have put locktite on those screws so I could protect the disc from coming off as well.
As an engineer myself, I am generally quite impressed by BMW engineering, but every now and then they do things that just leave me scratching my head and this is one of them. I also can see no reason to apply thread locker to those screws.

I also see no reason to design an air filter that requires fuel tank removal to change. I also see no reason not to use Dzus style fasteners on most tupperware. That would greatly decrease the removal time for the bodywork on fully faired bikes and keeps all fasteners captive which is great when doing a roadside repair in the rain and mud. However, it seems only aviation engineers know how to use Dzus.
 

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ok so what is the general consensus about the rotor replacement? do it at home or pay the shop to do it? I am only reading bad things on this thread. anybody got any good stories about rear rotor replacement?
 

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you wont hear good stories that's kinda the point the bad stories are to help others with maybe the same problem, I changed mine back in the day and never experienced any difficulty at all, whats the worst that can happen if you do it yourself, that's all you need to work out. if the dealer stuffs up the bolts they are still going to charge extra for the repair.
 

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you wont hear good stories that's kinda the point the bad stories are to help others with maybe the same problem, I changed mine back in the day and never experienced any difficulty at all, whats the worst that can happen if you do it yourself, that's all you need to work out. if the dealer stuffs up the bolts they are still going to charge extra for the repair.
I changed mine and it was pretty straightforward. I can’t recall if I posted my experience here or not, but I don’t recall having any significant issues. The main thing is to heat up the bolts to loosen the threadlocker.
 

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I had no real trouble beyond the usual experience replacing mine. I had to drill the sensor ring screws out of the old one but then it was going in the trash when done so I had no reservations about it. Heating the ring allowed fairly easy removal for transfer to the new rotor. If you have to drill out the 2 center retaining screws after stripping the head out, use the largest drill possible to take the top off and not remove the screw portion protruding from the hub as you can grab that with vise grips as you heat the hub to break the loctite and then remove them. Just don't melt the big seal in the process.
 
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