Seatpost Binding Bolt

[paulsc]

I hope this doesn't come across as a rant but I am really disappointed in the seat post binding bolt set up.  It is ugly and the welds seem really inadequate.  The bolt actually bends slightly when it is tightened and if you look at the design, it has to.  I wished Thorn would have just used a separate clamp which is what I am having done to my Sherpa next week.  I found a local builder who is going to remove the current binding bolt set up and I will install a clamp like a Salsa.  At least if I ever have a seat post slipping problem, I will feel more confident in tightening the bolt.  Now I worry the a weld is going to break or the bolt will.  Perhaps the welds on my bike were done on a Friday before a long weekend.  The system on the new Nomad is much better since it has a reinforcing collar and it looks great.   Considering how well thought out the Sherpa is, I really think this part of the bike could have been done better. 

I am sure this must be blasphemy to you Sherpa lovers, but hey, I am one too .

[jags]

can't say mine look's bad quiet neat actually and i never had a problem with the post slipping.
ah you must have got a dud i would say you would have endless troble with that particular bike better change it quick..
only pulling your leg  enjoy your sherpa it's a fantastic bike.

[malcon]

My XTC seems a similar setup and I have just snapped the bolt leaving the thread in place. Took some careful work with a hacksaw on the remnants to remove because of the way it deformed at the point of the break.

[paulsc]

Malcom,
Thanks for confirming my thoughts but I am sorry yours broke.  The switch ended up costing $25 including the seat bolt clamp.  Rattle can paint job provided by yours truly.  Here are the before and after pics:

[sloe]

Yep, same problem here and it's a RavenTour of 2007 if that's relevant. Seat post gradually slipped and I kept adjusting till the bolt snapped from fatigue. Cycled home like a BMX-er, would have been a right royal pita on tour.

My solution was to bulk out the seatpost with a bit of drinks can - greased with coppper grease - and that means the bolt doesn't flex so much. Also fitted an overlong bolt to enable cutting a slot. In my toolkit I've addded a wee bit of junior hacksaw blade, a wee screwdriver and a spare bolt.

I like your solution, paulsc. Except it makes the seat easy to steal, no?

[pdamm]

I have the same problem on my Raven Tour bought in 2006.  My solution is to carry a few spare seat post bolts and I have filed out where the head of the bolt sits so it doesn’t bend as much when it is tightened.  My seat post doesn’t slip but every time I take the seat out and put it back again I get nervous doing up the bolt.

Peter

[ians]

... and on my Raven Sport Tour.  Snapped the bolt.  I too carry a spare bolt - which is a ridiculous thing to have to do when you think about it.

ian

[kwkirby01]

I like your solution, paulsc. Except it makes the seat easy to steal, no?

Why would it make it any easier to steal? Kevin

[sloe]

I'm assuming that's a quick-release clamp, but maybe not?

[paulsc]

It is the non-QR version so it requires an allen.  I do feel more confident about this set up and it was the only significant flaw in it's design.  I hope Andy or Robin notice the replies and make some simple and inexpensive changes to their frames.

[blair]

A less expensive option is just to use an external nut, rather than the thread in the braze-on.
This can be retro-fitted by drilling out the thread in the existing fitting.
If the bolt breaks, replacement is trivial.

Ideally, you would use a nut that allows some lateral rotation, i.e. a cylinder drilled & threaded at right-angles to its axis.
This eliminates the stress raiser caused by bending of the bolt that is part of the problem.
Steel mountain bikes with QR seat-clamps sometimes use this setup.
Even a plain external nut will reduce the stress, as there will be a bit more compliance in the system.

Probably worth upgrading to a high quality stainless bolt, too.

[geocycle]

This seems a common problem.  I was riding with some guys on a charity run last year and one had his seatpost bolt break.  He was riding a Ribble.  We managed to call at some agricultural machine shop and botch it with an external bolt as described by Blair.  Before that he did 5 miles without sitting down and had some 60 to go so had lost all interest in preserving the threads on his frame.  There do seem to be a lot of cases reported on different bikes out in googleland. Maybe it is something that needs looking at by either using stronger higher grade bolts or some sort of shim to keep the sides parallel?

[john28july]

Hello
I have not yet had trouble of this nature although I have occasionally been worried about it. Inasmuch that I check the seatpost every ride and regularly regrease the post and bolt.
My own view on this 'problem' is that either the seatposts are not the perfect sixe or the person tightening the bolt is to blame for overdoing the tightness. I cannot for the life of me understand why in this day and age a simple fitting such as this cannot have extra strong bolts.
John.

[stutho]

I have to admit that I too have managed  to snap the seat binding bolt - indeed I have snapped two  The first was the standard part from SJSC and the second was a security bolt that I used as a replacement (it failed very quickly).  Both bolts went while they were being adjusted - has anyone lost a bolt while there were riding?

However I am also non too fond of "non-integrated" seat clamps.  I find them painful to adjust - or not up to the job.  So if I was given the option tomorrow to change I am unsure If I would take it. 

For the record:
My bolts were adjusted to 15NM on a pre-set driver  (not sure what the manual states so this might be high). 
I always use coppa slip grease on my bolts.
Bike has now seen more than 16000 Miles. Both bolts failed (it was in quick succession) about 8000 miles ago.
This was on my RST - My wife's RT has never snapped a bolt



 

[Tito]

Never had this problem, probably because I immediately installed a Pitlock - it took 20 seconds, and did not require any retro-fitting drilling.