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Stripped stem cap bolt

Old 05-01-18, 01:35 AM
  #1  
lyrictenor1
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Stripped stem cap bolt

Bought a used MTB recently, and didn't notice until I got home that whoever the idiot was that "worked" on the bike obliterated the head of the stem cap bolt. Any ideas on how to extract this? It's sunken into the stem cap (see pics), so please keep that in mind. Thanks!


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Old 05-01-18, 02:11 AM
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Try loosening the stem bolts and see if you can turn the entire cap counterclockwise by hand. The bolt will likely turn with it.
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Old 05-01-18, 03:41 AM
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That's what I'd try.
If that doesn't work, and you have an allen wrench you don't care about too much, you could try hammering one in there.
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Old 05-01-18, 04:28 AM
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maybe the bolt is fused, that's why it got snapped off by the previous owner and mebbe thats why he sold it

squirt some penetrating oil down there before wrenching it off
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Old 05-01-18, 05:50 AM
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An EZ-out type screw extractor should work to remove that bolt. https://www.amazon.com/IRWIN-HANSON-...ding=UTF8&s=hi
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Old 05-01-18, 06:25 AM
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One problem with Ez-Outs is that they are brittle and prone to breaking and if you break one off in your work you have multiplied your problem. I have had good luck with this type of remover, which seems more robust against breakage:https://www.amazon.com/Alden-8430P-G.../dp/B000H6PM32
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Old 05-01-18, 07:09 AM
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Originally Posted by dsbrantjr View Post
One problem with Ez-Outs is that they are brittle and prone to breaking and if you break one off in your work you have multiplied your problem. I have had good luck with this type of remover, which seems more robust against breakage:https://www.amazon.com/Alden-8430P-G.../dp/B000H6PM32
I really enjoy your posts and your wisdom. You have provided me with a great solution to a problem more than once.

Thank you.
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Old 05-01-18, 07:24 AM
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A quick thought:

I prefer the grabits when they fit (which this seems like it will), but a top cap preload screw really is close to a zero tension system... Grab a left hand drill bit (4.5-5mm), and drill from the center. Chances are good it will come out without provocation, but if the head snaps off, remove the top cap, and grab the stump with a pair of vise grips.
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Old 05-01-18, 07:34 AM
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Originally Posted by LesterOfPuppets View Post
That's what I'd try.
If that doesn't work, and you have an allen wrench you don't care about too much, you could try hammering one in there.
If it was my bike I'd try the opposite approach first. Try a brand new Allen wrench. That'll work more often than you'd ever imagine.

Next I'd check the headset real closely because the previous owner didn't like the way it was adjusted and he didn't understand how to fix it.
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Old 05-01-18, 07:45 AM
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There are lots of ways you can try to tackle this, some of which are mentioned above:

Loosening the stem clamp to relieve some tension
Grabit
Left-handed drill bit
New Allen wrench
Slightly upsized Allen wrench -- say maybe 7/32" instead of 5 mm, and maybe ball end
Tight-fitting Torx driver
Sacrificial Allen wrench and epoxy
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Old 05-01-18, 08:27 AM
  #11  
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That a top cap needs only a few NM of torque to properly preload a headset that the OP has one that has been gorillaed suggests the person who last worked with it doesn't understand how to use the top cap properly. I've seen far to many top caps (and their draw bolts) way too tight, especially ironic when the headset is also still loose (as in not loosening the stem's pinch bolts first)

At some point one could use a Dremel with a fiber cut off wheel to either cut a flat blade screwdriver slot in the draw bolt's head. Or when that fails just cut away the whole cap/bolt top. At some point one needs to get the job done and will use the tools they have on hand. Andy
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Old 05-01-18, 09:16 AM
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Back in my shop days, had one come in like this and after numerous failed attempts resorted to removing both binder bolts from the stem, VERY carefully cutting the headset spacer underneath (using the slot in the stem as a guide - only enough to insert a screwdriver and pry the spacer open), providing just enough space to slide the stem and top cap down to expose the sides of the top bolt, which I was then able to extract with pliers. This will relieve the tension on the top bolt, unless it's cross threaded, although you'll sacrifice a spacer in the process.

That would be a last resort, and will only work if there are spacers under the stem and the steer tube isn't flush with the top of the stem. You should be able to check that by sighting in the slot at the back of the stem - if there's no space under the top cap (which can be the case if the steerer is too long or the stack height is too low) this won't work.

Good luck!
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Old 05-01-18, 10:01 AM
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Wow, thanks all for the great ideas! I'll see if I have a chance today to give some of these a go!
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Old 05-01-18, 11:18 AM
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I have yet one more approach, if you have a Dremel tool. You can get cut-off disks with an arbor that fit the Dremel. Use the disk to cut a screwdiver slot across the top of the bolt. Cut the slot wide enough for a big old screwdriver. Use the screwdriver to remove the cap. Then you can replace it. (on edit: I see I'm two posts late: Andy posted the same idea. Oh well, here's a video
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Old 05-01-18, 10:49 PM
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Originally Posted by wschruba View Post
A quick thought:

I prefer the grabits when they fit (which this seems like it will), but a top cap preload screw really is close to a zero tension system... Grab a left hand drill bit (4.5-5mm), and drill from the center. Chances are good it will come out without provocation, but if the head snaps off, remove the top cap, and grab the stump with a pair of vise grips.
+!
I just did this with a stripped cleat bolt, and it came out easily.
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Old 05-04-18, 01:53 AM
  #16  
lyrictenor1
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Originally Posted by Kontact View Post
Try loosening the stem bolts and see if you can turn the entire cap counterclockwise by hand. The bolt will likely turn with it.

This worked a treat! Nice and easy. Thanks!
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Old 05-04-18, 10:14 AM
  #17  
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Originally Posted by lyrictenor1 View Post
This worked a treat! Nice and easy. Thanks!
Nice to not have to buy tools, eh?
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Old 05-04-18, 10:21 AM
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Originally Posted by Kontact View Post
Nice to not have to buy tools, eh?
R U serious?
You ALWAYS NEED new tools.
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