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Author Topic: Ahead stem possible stripped thread  (Read 697 times)

bryn

Ahead stem possible stripped thread
« on: 15 September, 2016, 05:39:14 pm »
I have a black Thorn branded Ahead-type stem.  The two horizontal bolts which clamp the stem to the steerer both have their heads on the same side - most other stems I have seen have one on each side.

Unfortunately somebody overtightened one of the bolts when the bars were turned during transportation and the thread appears to be stripped. Out of curiosity I reversed the bolt and found that it engages with the thread on what was originally its head side and appears to do a good job clamping up.

What puzzles me is how did this exert any  clamping action originally if both sides were threaded; surely turning the bolt would have done nothing to bring the two sides closer together?  I'm obviously  missing something here.

And any thoughts about whether I can safely continue to ride with the bolt reversed?  It seems to clamp firmly, and I  don't throw the bike around when I'm riding :) It has been suggested that I could try running a tap through the damaged thread, but I suspect there wouldn't be enough metal to work with.

Bryn
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Torslanda

  • Professional Gobshite
  • Just a tart for retro kit . . .
    • John's Bikes
Re: Ahead stem possible stripped thread
« Reply #1 on: 16 September, 2016, 02:28:24 pm »
For the cost involved versus safety, just change it.
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VELOMANCER

Quote from: trekker12 on 16 July, 2016, 08:54:33 am
Well that's the more blunt way of putting it but as usual he's dead right.

PaulF

  • "World's Scariest Barman"
  • It's only impossible if you stop to think about it
Re: Ahead stem possible stripped thread
« Reply #2 on: 16 September, 2016, 03:34:57 pm »
Quote from: Torslanda on 16 September, 2016, 02:28:24 pm
For the cost involved versus safety, just change it.

This. Stems are cheap, dental work less so.
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Brucey

Re: Ahead stem possible stripped thread
« Reply #3 on: 16 September, 2016, 05:31:13 pm »
There are any number of ways you could make the stem OK to use, but most of them won't be full strength, and/or they will leave jaggy bits on what ought to be a rounded part of the stem. These jaggy bits may cause nasty gouges in an 'off'.

If the thread is stripped and you want to make a good repair, you could use a helicoil thread insert in the stem, if the wall thickness of the housing is enough. Such a repair may be stronger than the original construction if it is done well.

BTW if the part has been overtightened the lug which normally accepts the screw head may have deformed. You should check it carefully for cracks. If it is cocked at an angle, it may appear to 'have a thread in it' now, from where the bolt has kissed it. Under no circumstances should you rely on this engagement.

cheers
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