Thomson Masterpiece and carbon rails
 

I have one of these seatposts inbound for my new build but am confused about using a carbon-railed saddle with it. What I believe to be true is:

• I can use a carbon railed saddle with the standard clamp provided the rails are round (7x7)

• I can use a carbon railed saddle with oval rails but only if I use the alternative clamp designed for them (Thomson lists that as designed for 7x10 even though most are listed as 7x9)

The reason for my confusion is that I've seen comments (not on Paceline) claiming success with using oval carbon railed saddles with the standard clamp.
Will appreciate feedback from anyone with experience on this front, thanks all.

unless they changed something...thomson clamps should accommodate oval carbon rails.

im trying to think if ive ever had a bike setup like that...i dont think i have...but the clamp design should have more than enough vertical leeway for 2-3mm of extra rail.

I've successfully used both straight and setback Thomson posts with 7x9 carbon rails on Fizik and Brooks C13 saddles. No issues, but I could see 7x10 rails or extreme seat tube/saddle angles requiring the alternative clampset.

Ive run my Fizik Antares 00 mounted on a Thomson Masterpiece without issue for the past three years.

I ran a SLR Kit Carbonio on a Masterpiece for years without issue.

Well damned if that isn't exactly the answer I was looking for, given that someone here has an Antares 00 for sale…

Much appreciate.

I have both clamps in my hands, and only the bottom cradle is different: it has slightly higher "shoulders" to encapsulate the rails better and it is machined to a higher tolerance so it is smoother.

The stock clamp is not particularly evenly machined, so you end up putting uneven pressure on the rails (you can see this in used posts by where the black paint has rubbed off in some spots on the clamps.)

This may or may not matter - "your mileage may vary" - but I can see why Thompson would suggest a special clamp.

I have been using a romin with oval carbon rails with a masterpiece setback seatpost for 3 years never a problem.

Arione CX carbon rail with thomson elite setback for years on one bike no issues.

I used a Thomson Elite setback post for years with Fizik and Specialized carbon railed saddles before I even realized that Thomson made a special clamp for carbon rails!

You should have no problem no matter which way you go.

thomson is a top/bottom clamp. so 7x7, 7x9, 7x10 doesnt matter...the rail clamps are made to fit a 7 width and the height (7, 9, 10) can vary.

maybe they want the special clamp for the 7x10 since it has a bit more cradle effect for the taller rail.

What about campagnolo seatposts?

Since I love beating a dead horse as much as the next person, here's some pictures of the 2 Thomson clamps. You can see the shape is more contoured on the deep rail clamp, and the uneven clamping (paint wear) from the non-contoured clamp.

https://i.imgur.com/Zv2v4KSl.jpg
https://i.imgur.com/f9nCuAWl.jpg