Seat clamps that keep coming loose

[Rich Aitch]

I've got a repeating problem with the seat clamps coming loose and tilting the saddle back at an awkward angle.
It happened with the Marin Lite alloy seat pillar which I had before. It would do it with any combination of saddle, bolt, spacers or adjusters, so I figured it was somekind of hairline crack in the pillar that was flexing and releasing the tension in the fastening, so I chucked it and brought a new replacement, only this does it too. I've torqued the bolt up to the maximum that this size of bolt should take but it keeps happening.
I wonder if it is a characteristic of this type of one piece swan-neck pillar, only it never happens with the very similar Chorus seat pillar on my road bike.
Any ideas?

 

[legrandefromage]

the grooved bits in the clamp and post may have lost their bite - you could try a dremel to bring them back to life.

 

[dyna-ti]

Or if it's the bolt loosening off then try a spring washer under the head.

 

[jax13]

as above - with a healthy dose of thread-loc or loctite on the clamp bolt if your certain your not gonna want to shift seat position that often.

its good enough for rifle scope mounts, why not a bike seat!

 

[racer x]

Could be the threads in the clamp at the top where the bolt binds in probably been done up to tight or done up to many times with out grease- The threads could be damaged causing the seatpost & saddle to keep coming lose

Try some medium loctite

 

[mikee]

paint on the seat rails flexing or wearing away ?
i have a viscount saddle that does this , turns out the rails are smaller than other seats

 

[Rich Aitch]

paint on the seat rails flexing or wearing away ?
i have a viscount saddle that does this , turns out the rails are smaller than other seats

Yeah, the measurements have all worn off but just on one side. I've been riding with this new saddle to get used to it before I put it on my Stumpjumper rebuild so it's pretty new, but it doesn't move when it's on my plain Marin seat pillar.