Can I use a saddle with carbon rails on my LOOK E-post?
 

Just as the title says, I'm trying to find out if I can use this combination of carbon saddle rails and the E-post on my 595. The LOOK manual says it is not to be used with carbon saddle rails, but it doesn't give a reason why. The Fizik Cyrano seat post is supposed to work great with their carbon saddles because it uses a full-length clamp to support the rails.

From the Competitive Cyclist product description:

"There are two critical elements to its functionality. The lower half of the clamp assembly is 45.5mm long. This means the bottom of the saddle rails are supported for this entire distance, distributing loads over a much greater area thus making rail breakage almost impossible and reducing clamping force in comparison to other seatposts."

http://www.competitivecyclist.com/za....ID=8843&MODE=

The carbon jaws on the E-post clamp do pretty much the same thing by fully supporting the top and bottom of the rail. Here's a pic:
http://bikeforums.net/attachment.php...hmentid=256196

Furthermore, if the carbon rails are 7x9mm (9mm vertically), and the rail grooves in the E-post clamp are for standard 7mm rails, shouldn't the shape of the rail grooves work with both?

Or is it just a matter of carbon on carbon and inadequate friction to keep the saddle from sliding?

I think you need a carbon specific bracket...

That's the problem..LOOK doesn't offer one and they don't really give a reason why their only E-post clamp doesn't work with carbon rails.

darn proprietary ****

Yeah, even if you could open it up, the shape of the curve that touches the rails is different. You don't want anything pinching wrong on a carbon saddle rail.

I don't think that's it. I mean, I have carbon bars and a carbon steering tube, with an alloy stem. And you could use the CF assembly paste to get a more secure clamp.

I'm looking at a Williams saddle with carbon rails, and their web page has this warning:

Only to be used with carbon rail compatible seatposts. Because the OCR rails have a 9x7mm ovalized profile seatclamps that close horizontally are not compatible,
nor are seatclamps with sharp edges that may damage
the carbon.

If I remember right, it has to do with the shape where the clamp doesnt press on the rails right, you have sharp points contacting the rails instead of a matching curve.

here is a terrible paint drawing I made from memory to illustrate what I mean. Red is a cross section of the rail. Black is a cross-section of the clamp. The one on the left is metal, the right CF.

http://bikeforums.net/attachment.php...hmentid=256205

Darn. I was hoping that the top and bottom curves of the 7x9mm rails were the same shape as the standard 7mm rails, but just elongated in the middle where the clamp doesn't touch. How does Fizik's Cyrano post work with both 7mm and 7x9mm rail profiles then?

When it says no carbon rails, it is usually related to the shape of the rails on the carbon rails on the saddle. I would say, this is one area you may better off taking the advice from the manufacturer of the seat post. If you have an event, more than likely, it will be catastrophic.

Yeah, I'm not trying to do anything stupid here...I don't even need carbon saddle rails. I just wanted to know the real reason why I couldn't use them other than because the manual told me so. Still wondering how Fizik's clamp can accomodate both though. Anyone know what the clamp grooves are shaped like and how they mate to both standard and 7x9mm rails?

I think it has to do with the shape of the clamps and the opening (See post #7) above. Is the saddle you want to get only available with carbon rails?