A little lube of some sort, let sit for a while...try again.

Otherwise, drill bits.

This is an option ... you may have to drill into it a bit to get the easy out in far enough. https://www.youtube.com/watch?v=K34RS6M11uw


You could try and pound in a torx bit that is slightly too large, I've had luck with that before as well


I have been an automotive technician for 12 years... I live in Maine, where well.... rust is king.... I have run into this kind of thing more times than numbers I can count to... insert greasy monkey joke here....

Edit: as others have mentioned you can cut a slit into the bolt that you can put a flathead screwdriver into....IF you can do that without cutting too much of the bracket you should use an impact driver with a flathead bit and a hammer to pop it free, then use a flathead to get it out. If its all carbon I wouldn't use the impact driver, instead I would get a flathead socket and use it on a 3/8 ratchet.

If it is aluminum you can try heating it up with a cheapo propane torch, just be super careful not to melt the aluminum... it shouldn't melt with a propane setup no matter how long you hold it there. Once its hot you can let it sit a minute or two THEN put the PB blaster or better yet GM heat valve lubricant to it. The heat will pull it in. Another trick is to put wax to it while its piping hot... the heat will pull the wax in and back the bolt out and free lubricate it a bit.

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"4 wheels move the body, 2 wheels move the soul"

Put some penetrating oil on the bolt. You can start with WD40 if that is all you have around but a specific bolt loosing oil like PB Blaster will work better (available at any hardware store, Home Depot etc). If there is a bolt opening on the bottom of the bar (i.e. the screw pokes out or there is a hole) put some penetrating oil in there too.

Edit - I should have looked at the picture first . . . . After you let it soak with penetrating oil for a bit, using a hammer to tap a Torx bit that barely fits into the bolt might give you enough grip. A Torx bit is more star like than a an Allen and should be able to latch onto what is left. It looks like this and you might already have one laying around without knowing it as they come with a lot of screw driver sets:





If the Torx does not work, you'll have to drill it out. Not as hard as it sounds nor a particularly big deal but if you need an explanation, that is a good sign you should take it to your bike shop ;-)

If the liquid penetrant doesn't work, use a series of progressively larger drill bits to remove the head of the bolt. Then you can get pliers on the remainder of the bolt which should come out much easier once the tension has been released. Another trick is to use a dremel or hacksaw to cut a slot in the top of the remaining bolt so you can fit a flat screwdriver in.

FWIW, I work on my cars in addition to my bikes so I have a lot of experience with stuck bolts. PB Blaster has never failed me. (Well, PB Blaster plus my impact wrench have never failed me . . .).

The number one rule on cars is don't even try to get a bolt off without hitting it with a penetrating oil first. You don't need to do that on a bike but everyone should have a little can of PB Blaster or Liquid Wrench around.

It is important to have your penetrating oil on hand in advance because, if you don't have it, you will try to get that stuck bolt out just one more time before heading to the hardware store. And, every fastener on a bike is so small that it is super easy to strip one out, especially on that "one last try." So spend the $3 on PB Blaster or Liquid Wrench now. It will save you sometime down the road!

Yep. That's exactly what happened. Dammit.

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Another trick from the car world. If you have a welder and know how to use it, place a nut on top of the stripped bolt head and weld the inside of the nut on. The heat will help loosen the stuck bolt and the nut will give you something to grab with a wrench. The tacking process should be minimal enough in both heat and duration to not damage anything else.

pb blaster all over it, let it sit for a day
dry the top off
get a dremel, cut a deep groove for a flat head screw driver (if possible)

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Anyone who works on bikes or cars long enough has this happen. It is actually not that all that hard to fix its just that the next steps require some tools and know how most people don't have. If the steps outlined here don't work, take it to your bike shop and they'll have it out in a couple minutes.

And, at this point no matter what you do you're going to have make a trip to the LBS anyway to get a new bolt since this one is not going back in even if you get it out so you might as well let them deal with the stuck one.

Bikes are easy because you can just put them in the car and go get help. If your car is jacked up and in pieces in the garage, you kind of have to deal with whatever comes up yourself ;-)

For the bolt that is stripped, or any that are on the verge of stripping, get yourself some "valve grinding compound" and dip the wrench before using it. It works wonders. It has a bit of grit in it that will latch onto anything.

Looks like the bolt might be past the point of using valve grinding compound, but for future reference when you feel you are about to strip something.

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marceves.com

Brutal, vicious profanity. Talk about what you did to the bolt's daughter last weekend.