mnkyman

Went mountain biking with a friend over at the Barton Springs Greenbelt in Austin, TX...we were planning on a ~2 hour, 20 mile ride...half a mile into the ride this happened:



Carbon Fiber seat post snapped resulting in injury on my knee (scrapped up) and tweaked my left hand pretty bad...spent about 20 minutes trying to remove the remaining portion of the seatpost so we could stick the rest of the seat back on and finish the ride, but weren't able to with the tools we had and ended up turning back. NO more CF Mountain bike seatposts for me.

Oh ya, and if anyone was wondering, it DID NOT snap where the frame of the bike starts...it snapped about 1 inch above that. Not exactly sure why...

127.0.0.1

it happens.

C Law

did you use a torque wrench when you installed it?

monk

I use a CF seatpost on the road, but not sure I'd want to use it on a mountain bike . . . even before I saw your post!

127.0.0.1

mountain bikes take serious odd loads when either landed improperly or simply crashed.

would never use a CF post on an MTB unless it was my race rig dedicated to racing. on my training bike or any other MTB, aluminum only....

just too many times the post would get nailed at the wrong
angle and weaken it

Pocko

I really like CF and I think it's a beautiful material in so many ways. I have used it with some of my work projects, and it just allows certain shapes and designs that are not possible with other materials.

But for me, NOT for mountain biking. It's just too susceptible to stress-risers from nicks and scratches... and when it lets go, it's almost always catastrophic and with no warning. I like a MTB that can be crashed, picked-up and thrown into battle again without worrying about material stress.

In controlled racing conditions with support and replacement contingencies, yes... but otherwise...

.

ed 

Carbon sucks...no really, it does.

Pocko

^ If I had to use only 6 words... yep, that's about it (for mountain biking).

bikinfool

What would that have to do with it if it broke an inch above the clamp?

OP--I allow no carbon on my mountain bikes after having seen several bars and seatposts and other carbon bits fail on others' bikes (and having my Trek OCLV bonding fail twice, that bike is ridden very infrequently and carefully now). I don't race (anymore), and want my bike to be able to crash with minimal worry. I know aluminum can break, too, but the one time I messed up an aluminum seatpost it bent and got me home.

born2bahick

I dunno, I've got an 05 carbon frame, seatpost, saddle and bars,
that say your a bunch -O- hacks He He

born2bahick

Where is the piece that was still in the seat tube?

born2bahick

Ha, carbon fearing mary's ha ha ha

ed 

I'll break my carbon foot off in yo saddle.

mtnbiker66

Buncha hacks.........

agarose2000

You're "lucky" that you seem to be riding a Cannondale and not a bikes-direct bike. You would have stoked the fires of the BD-haters out there, but seems like C-dale is relatively immune to hardware failure criticism, at least with regards to their road bikes.

JeffS

Out of curiosity, whose torque specs do you use? Those of the framemaker, the seatpost maker, or the clamp maker? Torque specs on bike parts seem to be quite hard to come by.

JeffS

Looks like a specialized seatpost. I've been wrong before though.

ca7erham

Deff. not a stock seat post. Unless cannondale is putting more expensive parts on cheaper bikes now.

bikinfool

Yeah, but you're in Kansas, too.

mnkyman

let me see if i can answer all the questions...

I don't know if a torque wrench was used on install as this was my friends bike, but as someone else mentioned, im not sure how much that would affect it since it snapped an inch above the frame

I personally wouldn't use a carbon MTB for general riding (especially after this experience)...i have carbon forks and seatpost on my roadbike, but that doesn't experience the type of stress a mtb would

The piece that was stuck in there, we were able to remove it with pliers...sorry no picture, but if your wondering if we had it in far enough, it was well past the "limit" marker on the stem ( i would say the piece was about a good 4 inches)

This wasn't a stock seatpost, however it was not specialized either...it was one of the more expensive companies...i can't remember, as the bike is my friends...

the only stock piece on that bike is the frame...everything else has been swapped

Pocko

Pro-rider turns up from overseas with preferred (brand new) carbon bar... installed it that morning... loaded three test bikes on a car rack as we normally do. At the end of one day I spot this nick while unloading the bikes.

It's probably fine (although no one would guarantee it safe for hucking or jumping)...
Pro-rider didn't want it back, so leaves it behind. No one else wanted it either, so it ends up on my commuter bike.

It's not on my MTBs because I just can't be bothered stuffing-around with paddings to protect it during rack transport. Didn't mean to sound too critical, but that's just me and my circumstances.

born2bahick

He He you'll never catch me on that heavy aluminum sled your riding.

ed 

Contraire...one day you'll be a freerider and wanna go huck yourself...but you won't wanna tear up the Epic or XTC...you'll be too proud of the 575 or Heckler to wanna huck it...so you'll break into my shop and do some "black-op's" hucking downtown one lonely summer night when I'm outta town. The only evidence of your mission will be the urine stain on my Komodo from that BIG OL' stair-gap at the Post Office

born2bahick

There's a law against riding on the sidewalks downtown.

dminor 

You guys need to come out here and boost the stairs at the Spokane Arena. Great fun.