By using a blow torch on the magura mounts the heat expands the ally . ive used this method on cranks to get them off the bb when the threads go....but what i had to do when the bolt snapped in the mount was get a fine drill bit and drill through the center of the bolt then tap in a verry little allen key heat the magura mounts from the side with the blow torch for roughly 30 seconds if that then turn the allen key hey presto the buggers out..... thats how its done chris x dave