Frozen rear recessed caliper bolt head... suggestions?
as the title says, i've got the recessed brake caliper bolt head frozen pretty well in the rear caliper bolt hole. i was able to unscrew the caliper and i tried threading a bolt through the opposite side and whacking it with a hammer to try and punch it out, but to no avail. it seems well frozen in there. not sure how i would go about drilling as there is no room, since the seat tube is in the way? and it seems drilling from the opposite side won't work since that side of the hold is smaller. you guys know what i'm talking about? any suggestions?
Is this a recessed brake caliper nut or bolt? Sounds like you're talking about the recessed nut that fits on the center of the seat stay tube. If this is correct, then consider the following steps:
1. Use some form of penetrating oil (i.e. Liquid Wrench, etc) and let it sit for awhile (try not to get any on the tire and rim, and be sure to clean the rim before use if you do).
2. If you can, carefully try to twist to the exposed part of the recessed nut with a pair of pliers in order to loosen it.
3. Thread a sturdy bolt through the other side, like you did before, and try tapping it out.
4. If that fails, place a 1/4 inch + thick stack of washers that fit over the outside of the nut (on the seat tube side) and then place a smaller holed washer on top of them. Next thread a suitable bolt through the washers and pull the nut out by tightening the bolt.
Note: I once had to drill out a recessed caliper nut frame hole "by hand" with very short drill bit (due to the lack of clearance between the seat stay tube bridge and seat tube). I used a small pair of vise grips in order to hold on to the drill bit). It was a pain, but it worked. You might, as a last resort, consider doing the same in order to drill-out the nut entirely.
thanks for the tips... its definitely the recessed nut and its sitting super flush against the hole so i think my only resort is #4. i'm not real good at drilling per se, so i would want to leave that as a last resort and prolly in the hands of an expert.
Originally Posted by FMB42
Dremel in a screwdriver slot if you already screwed up the inside hex .
Ya, consider fietsbob's good advice as well. Also, make darn sure that the recessed nut isn't brazed, soldered, or crimped to the frame. If you can twist it then it isn't brazed or soldered, of course. Crimped nuts will sometimes have visible crimping marks on the face of the nut. Btw, why are you removing the nut? If it's because you want to use a slightly larger diameter caliper post, then you might be able to drill the threads out and re-tap it to the size you need (you should be able to do this from the opposite side of the nut "head"). Yet another option would be to use a suitable non-recessed nut. You'd, of course, still need to drill out the recessed nut tho.