Seat Post sag. Which clamp works best?

[kandui]

My seat post is dropping on my carbon frame bike and it's driving me to drink. (I'll keep drinking once the problem is resolved). I had a 34.9 KCNC QR clamp which broke last week when I tried to close it. The bolt sheared off, that's how much tension I try to put on the clamp. I bought a cheap PRO clamp (looks like it's a Shimano product), but that doesn't work.

 

I don't need a QR clamp, I don't adjust my seat post during rides. This is for a Niner Air Carbon.

[patches]

aah, seems you weren't informed that KCNC stands for Kaak, Crap 'n Costly. Seriously. It's mass produced Taiwanese stuff and for some reason us South African's think it's high end top quality stuff.

 

The 2 best seatpost clamps I have had are Hope and Straitline. Neither are cheap, but quality and finish are excellent.

 

Quick question though. Have you got copper slip paste (or whatever it's called) on your seatpost?

 

And is your seatpost carbon or alu?

Edited November 19, 2012 by patches

[rouxtjie]

+1 for the hope....if can swop out the bolt and nut on the kcnc one that isn't made out of fakolaminium.

[_Daemon_]

make small shim out of coke can, and clamp then. Works very well on my thomson post / kcnc qr clamp

[kandui]

aah, seems you weren't informed that KCNC stands for Kaak, Crap 'n Costly. Seriously. It's mass produced Taiwanese stuff and for some reason us South African's think it's high end top quality stuff.

 

The 2 best seatpost clamps I have had are Hope and Straitline. Neither are cheap, but quality and finish are excellent.

 

Quick question though. Have you got copper slip paste (or whatever it's called) on your seatpost?

 

And is your seatpost carbon or alu?

 

I use Copper slip a lot to get the creaks out of my saddle and clamps.

I have Carbon Assembly paste which I can apply to the seat post itself, but I thought a thoroughly clean is better first time around. The copper slip I use for the clamp bolt and the space between the frame and the clamp.

 

Seat post is Alu. Having seen a seized Carbon frame and Carbon post combo, I'll stick to Alu

Edited November 19, 2012 by kandui

[droo]

Carbon assembly paste should sort this out. As far as seizing goes, this will happen with carbon / alu as well, so just make sure you take your seatpost out once a month or so. The carbon assembly paste will help to some degree with this as well, but better safe than pregnant...

[patches]

What diameter is the seatpost?

 

I ask, because I have an carbon frame with a 31.6mm internal seatpost tube diameter, but I used a 30.9mm alu seatpost and a CNC'd 30.9 - 31.6mm alu U.S.E. shim. It worked brilliantly.

[V12man]

I use Copper slip a lot to get the creaks out of my saddle and clamps.

I have Carbon Assembly paste which I can apply to the seat post itself, but I thought a thoroughly clean is better first time around. The copper slip I use for the clamp bolt and the space between the frame and the clamp.

 

Seat post is Alu. Having seen a seized Carbon frame and Carbon post combo, I'll stick to Alu

 

Rather use blue locktite on the clamp bolt or nothing - copper slip (any lube) makes a huge difference to the torque a bolt get tightened to and will hold - no wonder you broke the previous bolt - torqued too tight too often.

 

I have also seen a picture here on the hub of a niner with the same problem - resolved with 2 seatpost clamps... fwiw - i wonder if the seatpost is the correct diameter and that is why the shim works?

[patches]

I think (and I may be wrong, but) what could also make a difference is the surface of your seatpost.

 

Some alu posts have a fairly smooth surface finish, whilst the CNC'd ones like Thomson have those lateral lines from the lathe.

 

I think the reason the U.S.E. shim I have works so well is that it also has that surface finish, and a collar (so it doesn't slip in). That finish grips the seatpost really well.

[kandui]

I have a Thomson seat post. I have a 34,9 clamp for the Niner Air Carbon. The size is right. I am going to try a Hope clamp and see whether it does the trick. I take my post out regularly to clean it and also remove the grit from the bolts which hold the saddle in place.

I used a double clamp on another frame i had and that worked pretty well.

[Gravity]

I had same problem until I got Hope clamp.....it is fken irritating.

[Thug]

Hope

[Paul Ruinaard]

KCNC = lightweight bolts. Lightweight = not strong. You are going to cut your seatpost in half or crush the top of your carbon frame if you are not careful. Ask me I have down that. Gte a carbon collar as well, as they often torque laterally. Use carbon assembly paste and the problem goes away. I had this on my road bike with a specialized post in a Spec frame with a Spec clamp and it would slip down. With some assembly paste it goes away. Ask the bike stores where they get it.

[RockCoach]

Another Hope convert. Get the fatter one of the two. The narrower one works but I found it ever so slightly ovalised the seat tube and thus influenced my dropper post which would not function when tightened.

[NINER_boy]

Kandui,

 

Get a Thomson seatpost clamp!!!

I have the exact bike and components as you (in this regard).

 

Steps to follow:

1. Remove all components

2. CLEAN the inside of the frame and the seatpost

3. Apply ParkTool Supergrip carbon and alloy assembly compound to the inside of the frame, the inside of the seatpost clamp and on the seatpost (a thin layer is OK).

No need for double clamping here...

 

Reassemble and torque to spec.

 

Whoilla

 

Enjoy

Edited November 19, 2012 by NINER_boy

[RacerX]

Kandui,

 

Get a Thomson seatpost clamp!!!

I have the exact bike and components as you (in this regard).

 

Steps to follow:

1. Remove all components

2. CLEAN the inside of the frame and the seatpost

3. Apply ParkTool Supergrip carbon and alloy assembly compound to the inside of the frame, the inside of the seatpost clamp and on the seatpost (a thin layer is OK).

No need for double clamping here...

 

Reassemble and torque to spec.

 

Whoilla

 

Enjoy

Same here. The carbon paste (gritty red paste) is the bomb. You only need to lightly torque the clamp (especially on a Thomson post) to make it rock solid and never move.