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I have a Campagnolo 11 speed Athena setup. I am enjoying a noisy creak which I suspect is located in my chainring bolts. I have replaced all of them, except the one that screws the chainring to the crank. That one is stuck. I tried to unfasten it, but I messed up the bolt. My hex key can not grip it now.

Do you have any ideas on how to solve this?

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    Screw extractor (aka easy out). – mattnz Aug 3 '15 at 21:16
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    A little late now, but first clean the crud out of the recess in the bolt head, then use a tight-fitting wrench inserted all the way in. (Throw away hex wrenches with worn tips.) If it's recalcitrant, soak with penetrating oil for several hours before trying again. And use a manual impact driver (the type you hit with a hammer) if it's still stiff. But if the bolt is already completely rounded out then this is no longer possible. – Daniel R Hicks Aug 4 '15 at 2:03
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I would underscore taking it to a trusted local shop to remove the bunged screw.

But I would also suggest that if you've tightened the other four that your creak is NOT coming from the chain rings but probably from either your pedal, your cleat or your shoe. Also if you haven't lubed the chain for awhile you can try that as well.

A creak from the chainrings will almost always be heard when pedaling on both sides. This will also be the case with the crank bolt as well if it isn't properly torqued.

In one case it was the right LEVER that wasn't tight enough. In another the front derailleur. But shoes and cleats are the most common.

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You could try using a brand new hex key, some brands may be slightly larger than others. You could see if a slightly larger non metric hex key, or hex key bit can be hammered into the recess. For example, a 7/32" hex key is about 5.6mm. I believe some nicer metric hex key sets come with 5.5 mm sized keys.

If you can buy or borrow a dremel tool, you might be able to cut a slot in the head of the frozen bolt that you can fit a plain tip screw driver into.

Another alternative is to drill out the bolt and use an easy out.

Before trying to get it out, I'd put the cranks in an oven and put it on 150 to 200 degrees. Aluminum has a coefficient of thermal expansion much greater than steel, and so this will make the bolt a slightly looser fit in the hole.

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Personally, considering the cost of a replacement crank and/or chainwheel, I'd probably take the bicycle to a trusted local bike store and pay them to fix my mistake. If you make it worse, that's false economy.

You could slot it with a Dremel, but before I did that I'd try a Torx bit first. Sometimes it is possible to force a Torx bit into a stripped Allen/hex-headed screw, and if the bit is short enough you might be able to force it in using a clamp of appropriate size. Unless you protect the area around the bolt and have some solid Dremel skilz, I'd say the chance of marring the chainwheel and/or crank is pretty high if you go the Dremel route.

Heating the bolt with a butane torch lighter or propane torch could help, but I would not put the whole crank into the oven. You might try penetrating oil, followed by some heat, followed by some more penetrating oil, etc. Be careful not to overdo it; I would start slowly, and go slowly. I should note, I'm not a metallurgist, but I would think that too much heat is as bad as not enough.

Too, I've never tried this, but it might give you some ideas.

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