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Just put together this bike which is a VB-r-068, i've tightened it to the point where I can't tighten it anymore yet I can still tilt it and what not. I've greased the threads since I thought that might be the issue. This is steel rails I believe, it is the EC90 "power saddle".

Seat post showing the hole for the clamp (click for larger):

Seat post showing saddle mounting hole

Clamp mechanism parts (click for larger):

Seat clamp parts

View of the clamp holding the seat rail of the mounted saddle (click for larger):

Saddle mounted to the seat post

View of the mounted saddle from behind, showing the clamp (click for larger):

View of mounted saddle from behind, showing the rail attachment

Assembled clamp mechanism (click for larger):

Clamp mechanism assembled

This imgur gallery contains a few more photos.

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  • That just looks like an extremely bad design. Looks like there is nothing which prevents the bolt from turning? Not even serrations? So the same force/torque you use to tighten the bolt can also be used to tilt the clamp.
    – Michael
    Apr 27 at 9:18
  • yes that's correct unless i'm missing something, the round plastic bit literally just turns when i put down slight force which causes the tilt Apr 27 at 9:39
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    Are there any torque values listed on the clamp area, or is any info available from the manufacturer. I would suggest figuring out the max torque and ensure you are using enough. Also, maybe try assembly paste to increase the grip.
    – Kibbee
    Apr 27 at 14:35
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    I'm not familiar with this clamp, but is it possible you're missing a part? Did you get it new or used ?
    – Criggie
    Apr 27 at 20:47

1 Answer 1

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This seems to be a style of clamp that is not specific to the VB-r-068, or even the company that makes them (VeloBuild?). Here is an example sold by Trek:

Exploded view of the Bontrager saddle rail clamp for an Emonda seat post

It appears that the most likely sources of trouble for this part are not having it tightened enough (I've found equivalent parts marked 10-12Nm or 10-15Nm, which is quite a lot) or having some contamination inside the clamp, as this person notes in his review of the VB-r-068:

It seems your best course of action would be to take it apart and thoroughly clean/degrease the contact surfaces, then reassemble it and make sure it's tightened to at least 10Nm. (Source for 10-12Nm, Source for 10-15Nm)

I did stumble across (meaning I can't find it again) someone who claimed they'd purchased a clamp that had the circular wedges too deep for his seatpost, so they made contact in the middle before clamping sufficiently, but that shouldn't be a problem for the clamp that comes with the bike.

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