..so I'm thinking about swapping it for another one with the K.ium rail.

Can someone tell me if that would likely fit?

The carbon rail just doesn't fit into the clamp channel/groove properly and keeps moving from level after I sit on it.

Bike is a 6.9 Madone SSL, and I kind of want to keep the standard seatpost as it matches nicely.

If suggesting I keep the saddle and swap the post, what seatpost would you recommend?

Thanks for any help.

Is it just a case of getting the right sized rail clamps to fit your saddle?
Bonty used to sell them as an accessory

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Official cafe stop tester

I didn't know that could be done? Thought you'd just have to replace the whole post.

Does anyone have any experience with this?

Probably easiest for me just to buy another seat but I want to make sure the standard K.ium rails are smaller in diameter, and will properly fit my Bontrager seatpost.

If it's a side-load clamp, then yes you will have to replace the clamping mechanism. If you can find one, then do that otherwise you might just need to replace the post. Go for a 2-bolt vertical load post to make sure you're compatible with both carbon and metal rails. Whatever you do, DO NOT TIGHTEN YOUR CURRENT CLAMP TO THE RAILS. You will damage the carbon and possibly die a brutal death at high speed.

http://bontrager.com/model/06096 (Details tab)

Specifically, you want part #421564, which just replaces the outer "ears" of the clamp with ovalized ones.

Now as for the rules on saddles:
Metal rails are 7x7mm and will work with both side-load and vertical-load clamps.
Carbon rails are 7x9mm (or 7x10mm depending on who you ask) and are compatible with vertical-load clamps. Most manufacturers sell ovalized clamps for carbon rails and side-load clamps.

you most likely can not replace the post. i may be wrong but im pretty sure the 6.9ssl has a trek proprietary seat mast cap on those frames. your best option would be to find out if your local dealer can find a new clamp like the one above

Thanks for the reply. I've already tightened the clamp to the rails and was going to go for a flat ride to test it out this weekend!
It seems to hold fine at the moment, but as mentioned, has already moved from level when I was putting weight (sitting) on it.
I didn't tighten to anywhere near the recommended 16nm torque however, so apart from cosmetic, I shouldn't have damaged it.



The clamp I have looks exactly like the one in the first picture from your link.

This site here seems to have what you recon I'll need.

http://www.cotswoldcycles.co.uk/compone ... 0mm-rails/

Sounds like this will be the best/easiest way and hopefully an easy fix!

I just read somewhere that Trek does not recommend using carbon rails with any of its post.

Is this even going to be safe?

I ran a braided rail Antares on my 6.9 ssl no issues you just need the clamp adaptors for the rails. There are 3 versions, round, 7x9 and 7x10. They cost about £10 IIRC. They are commonly referred to as "ears"

OK, thanks.

So I def need the 7x10 adapter to fit the bigger 7x9.6 mm Antares rail, right?

Yes, the 7x9 fits the prologo nack rails the 7x10 the fizik ones

I emailed Trek directly, linking them the saddle, and got this reply:

"The Fizik saddle in question uses a 7x9mm clamp. You will simply need the 7x9mm clamping ears. These are part number 406923."

Now I'm confused!

From Fizik's specs:

Shell: Rilsan Carbon Reinforced - O.M.D.
Rail: Carbon Braided 7x9mm
Cover: Black Microtex
Thigh Glides: Black Gummy Microtex
Weight: 155 gr

Looks like they are 7x9mm.

My bad, all I know there are 3 versions one for tubular metal rails, one that fits oval rails like the prologo and one for the fizik. I presumed those dimensions off the bontrager site to be that.

Basically I went into a trek dealer and asked for the appropriate ears for my saddle. As I spend there regularly they just swapped them for me.

I know it's an alien concept to some going into a bike shop but sometimes it's the best solution

Only 2 supposed suppliers of Bontrager in my city and they're both shite. Posting on forums for me, is a last resort.

Where are you?