BM state loud and clear these bolts are not to be removed.
Since I know more than BMW I pressed ahead anyway. The calipers distorted causing the pads to drag on the discs. Result - total loss of confidence in the front brakes and two new calipers.
Expensive mistake, but I wasn't prepared trust my safety and that of my partners to a braking set up I knew to be faulty.
If you do decide to proceed remove and replace the bolts one at a time. Start with the inner bolts [assuming you want to replace all four bolts/caliper] and work out - I didn't. I don't think torque values are given for these bolts since they're not needed.
Do a Google search and you'll soon find someone who'll supply the correct length bolts.
I've already done that, 2 years ago, and I'm still alive. The thing is, I didn't manage to find bolts with a long flat bit, so the ones I've fitted have a longer thread that touches the inner pad (I've filed it down a bit). Looking for a better solution....
I’ll confess, I did it with my old Airhead and my current 1100. I obtained over length S/S bolts and cut them down so they had exactly the same length of shoulder as the originals. They were replaced one at a time and have been fine for 2 years now.
I can’t recommend you do it, if you do the risk is all yours