What seatpost clamp for 27.2 post?

First ride on new bike today. Had a few issues with the post slipping even with the clamp tightened to the correct torque.

Cut a long story short; after a few stops to re torque and then over tighten (I know, I know) I sheared the bolt and had to do the rest of the ride without the saddle.

Both sides of the OE clamp met when the bolt tightened so i’m looking for a clamp where there’s a gap between each side that will allow me to go tighter.

I’m going to have a look at Hope, but i’m open to any suggestions. My other bikes have 31.8 posts so I can’t swap one out.

steel,alu,ti,carbon,plasticine,bamboo or bone china???

clamp size depends on the frame seat tube outer diameter not the seat post.

Also 31.8mm is not one of the standard seat post diameters, it is a standard frame seat tube outer diameter and common on aluminium frames with 27.2mm seat posts.

31.6mm is one of the standard seat post diameters.

The size of the camp is normally written on it somewhere. Failing that check the manufacturers website or measure the frames seat tube.

If you are clamping a clamp that tight I suspect you are over tightening it. There are other reasons and cures and no need to clamp that tight.

It’s carbon ‘wrapped’ according to the Cannondale website. The carbon is gloss finished which I suspect isn’t helping.

Andyl, the only info on the clamp is the torque setting. I know I over tightened it as it said 5nm and I nipped it up a good half a turn over that. After several stops to get the post back to the correct height and re tightening the clamp the bolt ‘cried enough’ and sheared.

For clarity it’s a 27.2 post in an Alu frame. The clamp itself looks like alloy. The problem is that it is designed for each side to meet when the clamp is tightened to 5nm. This would be fine if that clamped the post firmly, but at that setting I can still move the saddle from side to side.

I’m working on the basis that a clamp that has more of a gap between each side would allow me to tighten a bit further and stop the movement on the post.

Maybe I should have put this detail in my first post. Even i’m yawning now though 😉

So.. suggestions, cures, alternative clamps? I am listening.. 😀

Carbon assembly paste.. it’s got little granules in it to stop things slipping…

Thanks Khani 🙂

No probs, and try a Hope or Salsa clamp, they’ve never let me down..

Do you want a QR or bolt type clamp?

I use hope clamps on most of my bikes. They have aluminium bolts so you really can’t overtighten them (or they snap) but I have never had a problem and it’s nice to have a ‘fuse’ in there.

I also have a Thomson bolt up clamp which is lovely.

But tbh I have never had a problem with cheap clamps that came with bikes. The faces meeting does sound odd. But check your warranty as some makes can be funny about changing things like this.

Salsa make very nice QR clamps.

And yes, use carbon paste but first de-grease the tube and post with something like IPA as the manufacturer will probably have used some grease to prevent corrosion.

also there should not be much play with the clamp undone. If there is a lot then it suggests the post is undersized or tube oversized and I would be going back to the shop to get it checked.

For size – you still need to check the actual diameter of the seat tube in the frame. 31.8mm is the most likely though with 29.8/30mm being common for steel.

andyl, khani, thanks (again).. 🙂

browsing the Hope ‘site now

If I had tightened a seat clamp so tightly that the bolt broke and yet the post was still slipping I think I would check that the seatpost isn’t slightly undersized by putting in another 27.2 post and seeing how that fits .

If tha faces are meeting around tha alloy frame your clamp is too big. Carbon assembly paste is your friend.

Have hope and Salsa clamps both ace. I’ve always junked the cheap clamps that come with frames, always seem to slip.