Author Topic: Audax seat-post clamp bolt sheared  (Read 2410 times)

ben n

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Audax seat-post clamp bolt sheared
« on: September 10, 2016, 09:15:19 PM »
Hi
I just spent a couple of cursing and sweaty hours removing sheared bolt from my Audax's seat-post clamp. I have the one where the clamp is welded onto the frame, not a separate collar.
It looks like the faces that the bolt tightens onto on the two halves of the clamp are not parallel to each other, so the bolt is forced to bend when tightened. No wonder it sheared.
Some questions:
Can anyone recommend a collar seat-post clamp that will fit? - probaby not as welded on bits are in the way.
Can anyone recommend a quck release clamp I can lift the QR from and slot into the welded on clamp on the Audax seat-post?
Any other suggestions to avoid this problem? I have a Sherpa with same clamp, am keen to avoid more sweating and cursing!
Hope all the above makes sense, many thanks for any suggestions...
Ben

mickeg

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Re: Audax seat-post clamp bolt sheared
« Reply #1 on: September 10, 2016, 10:49:56 PM »
I bought my Sherpa frame used, the previous owner told me that he had a frame builder cut off the clamp, paint it and then he put on a Salsa brand clamp.  If it was me, I would have spent several careful hours with a hacksaw and file instead of paying someone, but I have pretty good tool skills.  That said, you don't need much skill to use a hacksaw, but you need some skill to make it look nice in the end.  The key is to not be in a hurry and be very very patient.

My nomad has the original clamp, I have not had any reason to change it.  But, I wanted to be able to remove the bolt if it broke, so I cut a slot in the bolt so that I can use a slotted screwdriver in the bolt to remove that half of it if it breaks.

I used to carry a spare seatpost bolt, but I figured out that my stem cap bolt will substitute, so stopped carrying one.

I would not want to come out of a store and find my seatpost and Brooks Conquest has gone walk-about.  Thus, I do not recommend a quick release.  On one tour where I had heard that there may be a few areas where theft could be a concern, I used a thin gauge steel cable between my saddle and a cantilever brake bolt as an extra precaution against saddle loss.

Good luck.

ben n

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Re: Audax seat-post clamp bolt sheared
« Reply #2 on: September 11, 2016, 09:44:06 AM »
Thanks for this. My current plan is just to use a M5 nut and bolt all the way through the brazed-on clamp assembly, so if it snaps I can just replace with another without faffing. The threading in the brazed-on clamp seems dodgy, there is a lot of resistance to a new bolt, presumably as it has been repeatedly tightened and loosened with the bolt at a off-centre angle.

If all else fails it will be hacksaw and Dremel time, but I would rather avoid that if I can!
Cheers
Ben

mickeg

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Re: Audax seat-post clamp bolt sheared
« Reply #3 on: September 11, 2016, 01:51:58 PM »
I have no idea if this would be a good idea or a bad idea, but if you have a M6 tap, you could re-tap the threads.  The reason that it might be a bad idea is that if you cut too much metal out of the clamp, the remaining metal in the threads could shear out of the clamp when you crank down on the bolt.  Without seeing what it looks like, I am inclined to think that this is an option that I would only try as a last resort before cutting off the clamp. 

An M5 bolt might not be strong enough, if you use this option, you might want to carry a spare M5 bolt in case it breaks.  On my Thorns, I store spare M5 bolts in the bottle generator mount on the front fork.

Good luck.

ben n

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Re: Audax seat-post clamp bolt sheared
« Reply #4 on: September 12, 2016, 04:33:53 PM »
Thanks again. In the end I just forced thru an M6 bolt from the wrong side to re-groove threads, and then bolted seatpost back in with M6 bolt from correct side. I have hacksawed a groove into exposed end of bolt for easy removal should it break, and will carry spares. Seems OK, touch wood - the threads bit nicely and I will now be very cautious about over-tightening.

It does seem like not such a great design for seat-post clamp - as evidenced that on newer models of Sherpa and Audax they do not seem to do it any more!
Cheers
B