# Is this seatpost safe with carbon rails?



## pontoon (Aug 4, 2015)

See Picture here


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## looigi (Nov 24, 2010)

Looks iffy to me. Carbon rails are usually oval, 7mm wide and 9mm tall. Clamps that pinch the rail from top and bottom and conform to the 3.5mm radius are usually compatible of they have no sharp edges. In that pic, it doesn't look like the clamps conform to the 3.5 mm radius very well.


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## pontoon (Aug 4, 2015)

The clamp contours the rail pretty well. I didn't tighten super hard so that I won't damage the rail (torque wrench still in the mail). The clamp fits most of the way around and then gives a small amount of daylight thru as it gets near the end of the curvature (a fraction of a mm). My main concern was that the surface area of the clamp that touches the rail is not large. I wonder if this will cause undue pressure on some parts of the rail, leading it to a greater likelihood of failure.

Edit: pics here: - Album on Imgur


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## ibericb (Oct 28, 2014)

Check on the seat manufacturers recommendations. Many require a different seat post/clamp for the reasons looigi noted, e.g., Bontrager refers to those type of carbon rails as "oversized" and requires an "oversize-rail compatible seat post clamp". Specialized notes, _"Oversized 7x9mm carbon rails are not compatible with seatposts equipped with side-load clamp mechanisms for 7mm round rails"_.


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## tvad (Aug 31, 2003)

^Beat me to it.

Post deleted.


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## pontoon (Aug 4, 2015)

It's a chinese carbon saddle and seatpost... Didn't come with a manual or anything. I can try contacting them. I'm guessing their answer will be "yes" whether it's a good idea or not.


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## tvad (Aug 31, 2003)

pontoon said:


> It's a chinese carbon saddle and seatpost... Didn't come with a manual or anything.


Follow the guidelines of Bontrager and Specialized...for your own safety.

Under no circumstances would I use that seat post with ovalized (or oversized) carbon rails on a generic Chinese saddle. No way.


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## ibericb (Oct 28, 2014)

tvad said:


> Follow the guidelines of Bontrager and Specialized...for your own safety.
> 
> Under no circumstances would I use that seat post with ovalized (or oversized) carbon rails on a generic Chinese saddle. No way.


Me neither. For that matter, I wouldn't use a no-name Chinese saddle with carbon rails, period. But that's just me.


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## Ventruck (Mar 9, 2009)

tvad said:


> Follow the guidelines of Bontrager and Specialized...for your own safety.
> 
> Under no circumstances would I use that seat post with ovalized (or oversized) carbon rails on a generic Chinese saddle. No way.


Yet I did for years...ok, well it was with a Trigon saddle which passes as as official more than no-name, but it didn't even have oval rails and I still use it to this day.

The Bontrager and Specialized saddles in question clamp from the sides. This does create an obvious incompatibility with oval rails. The vertical clamp design in OP's pic usually works. It's the sharp edges like mentioned that have to be watched out for and/or obvious improper seating. 

One issue I do find, though, is the setup can get creaky with that clamp design. The posts that use round yokes work way better with my saddle. 

I also think people make too much the mode of failure with a carbon saddle. Unless the rider was on the far front/rear edge during a fracture, or doing jumps, it's not going to be that big of a deal. He's going to drop what? an inch or so? It's not like that bolt head in the front is gonna blow his balls right open either.


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## pontoon (Aug 4, 2015)

Interesting alternate view. Here is more info I found in case folks are curious: 

http://forums.roadbikereview.com/co...carbon-rail-compatible-seatclamps-268948.html

I don't understand why the saddle clamp doesn't grasp more surface area of the rail (probably weight savings?)... I'm 127 lbs, so I'm not exactly carbon fiber enemy #1.


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## tvad (Aug 31, 2003)

Ventruck said:


> I also think people make too much the mode of failure with a carbon saddle. Unless the rider was on the far front/rear edge during a fracture, or doing jumps, it's not going to be that big of a deal. He's going to drop what? an inch or so? It's not like that bolt head in the front is gonna blow his balls right open either.


If a rider has a catastrophic accident as a result of the failure of the saddle's carbon rail(s), then he/she will likely have legal recourse against a company like Bontrager or Specialized (or other name brands) that carries liability insurance as a matter of doing business.

I am doubtful such recourse would be available from a Chinese manufacturer of generic saddles.

This is a personal choice. Clearly, some riders such as yourself have no issue with using a generic Chinese product, and are willing to accept the risk involved...and this is certainly your prerogative. 

I have a different point of view. So, each of us owns equipment that makes us comfortable within our risk tolerances.


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## Roland44 (Mar 21, 2013)

ibericb said:


> Me neither. For that matter, I wouldn't use a no-name Chinese saddle with carbon rails, period. But that's just me.


Same here, it's just doesn't feel right.


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## pontoon (Aug 4, 2015)

I read some more from Selle SMP, which is the saddle I might upgrade to. They recommend something like 32mm total length of contact between saddle rails and seatpost clamps. Mine are definitely short of that. I would probably chance it on metal rails, not on carbon. I'm going to get rid of the seatpost and find a different one.

More info: http://www.sellesmp.com/smp4bike/images/stories/istruzioni_montaggio/libretto_GB.pdf


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## ibericb (Oct 28, 2014)

pontoon said:


> I read some more from Selle SMP, which is the saddle I might upgrade to. ... I would probably chance it on metal rails, not on carbon. I'm going to get rid of the seatpost and find a different one.


FWIW, IMO a very smart decision.


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## pontoon (Aug 4, 2015)

Having a heck of a time finding any carbon seatposts that match SMP requirements...


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## ibericb (Oct 28, 2014)

Some seatpost manufacturers (.e.g, Bontrager, Ritchey) offer separate clamps to adapt their posts to oversized oval carbon rails.


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## pontoon (Aug 4, 2015)

In searching for adapters, I found a carbon lower half that meets the requirements of SMP... So I can keep my seatpost and don't have to use some stupid branded seatpost.


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## ziscwg (Apr 19, 2010)

take the money you saved buying a chinese no name saddle and buy a Thomson Masterpiece seatpost with oval rail clamps. 

Sometimes I really wonder about going cheap. If that seatpost breaks your rail out on a ride, you better be good at riding out of the saddle


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## tvad (Aug 31, 2003)

pontoon said:


> So I can keep my seatpost and don't have to use some *stupid* branded seatpost.


To be precise, a seat post can't be stupid, as that adjective refers to a lack of intelligence or common sense. The _owner_ of the cheap non-branded Chinese carbon seat post...well...


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## Ventruck (Mar 9, 2009)

ziscwg said:


> take the money you saved buying a chinese no name saddle and buy a Thomson Masterpiece seatpost with oval rail clamps.
> 
> Sometimes I really wonder about going cheap. If that seatpost breaks your rail out on a ride, *you better be good at riding out of the saddle*


Quite frankly he should be no matter what:

http://forums.roadbikereview.com/components-wrenching/riding-saddle-post-made-me-lazy-348936.html

:wink:


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