I have just snapped the rails on a Phenom Pro after 5 km of use. It's on my 'cross bike at the moment, but I was planning to use it on my MTB. I wanted to try a dis/re-mount to see what the saddle would feel like for cross. On the packaging it says that it should be fine for 'cross.

I sent an e-mail to the Specialized Concept Store where I bought it (with pictures attached), and now they tell me that it snapped because I used the wrong clamp.

The seatpost is a Thomson Masterpiece. According to Thomson (http://bikethomson.com/seatposts/masterpiece/#FAQ):

Q – What size saddle rails work with Masterpiece seatposts?
A – Saddle rails from 7 x 7mm up to 7 x 10mm work well with Thomson Masterpiece clamps.
Q – Will carbon saddle rails work with a Masterpiece seatpost?
A – Yes, our clamps are very gentle to carbon saddle rails.

The rails of the Phenom Pro are 7 x 9 mm, so I really don't see the problem here. Anyone else with similar issues? Is the Masterpiece not fit for the Phenom Pro?

The problem is probably with the saddle. You can mount almost all saddles safely with a Thomson masterpiece.
I don't know the Phenom Pro but i guess it's a carbon railed saddle.
You shouldn't mount a carbon railed 7*9 saddle on a side clamping seatpost.
It's fine with the Thomson clamping mechanism as it clamps from top and bottom.
The only thing that could be a problem is an irregularity on the clamps that could have stressed the rails and cause the break.

How exactly did it break? Did it snap in the clamping part (then it could be the seatpost) or did it snap outside the clamping part (than the problem is with the saddle)?

Edit: Note to self: READ title

I am using the same saddle on Thomson Elite (same clamp as masterpiece just a bit fatter) with no problem since 6 month om my mountain bike (Giant Anthem X). I weight 72kg (75 with gear) and I am quite aggressive on the downhills... the saddle is good as new.

I do not thing they are incompatible. Just you have to be careful with the torque when tightening. Are you sure it was not overtightened?

Regards,
Stefan

Very sure, I used a Park Tool torque wrench.



Here's a few pics:

http://img42.imageshack.us/img42/8306/2 ... 115829.jpg

http://img42.imageshack.us/img42/8306/2 ... 115829.jpg