Bike Forums - When seatposts fail (not pretty)

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- - When seatposts fail (not pretty) (https://www.bikeforums.net/singlespeed-fixed-gear/381007-when-seatposts-fail-not-pretty.html)

Quote:

Originally Posted by dobber (Post 6023158)

Aren't there some weight limitations often associated with titanium parts. I seem to recall limitations with Crank Brother pedals, Brook saddles and Phil bottom brackets.

Crank Brothers has a 185lb rating on some of their Titanium pedals http://www.crankbrothers.com/candy_4ti.php

Not sure what you're talking about, but you might want to check out this webpage:
http://www.sheldonbrown.com/frame-materials.html

Just a little quote (I suggest to read the article, it's great):

Quote:

identical steel vs titanium frames would be about equal in strength, but that the titanium frame would be about half the weight and half the stiffness.

Quote:

Originally Posted by dobber (Post 6023158)

Crank Brothers has a 185lb rating on some of their Titanium pedals http://www.crankbrothers.com/candy_4ti.php

more CYA legalese...doesn't mean they break at 190.

perhaps this is better stated (from the campy website, 80kg=176lb):

"Last year I weighed 80 kg and now I weigh 83 kg. Can I still use Campagnolo products, or am I too heavy?

There is no clear dividing line defining when someone is "too heavy" for Campagnolo products. Many factors need to be considered.
Campagnolo products were designed for "racing" type bicycles used on smooth asphalt roads or tracks. Any other use of Campagnolo products is improper.
Magnified stresses and loads caused by a "heavy" rider, coupled with forces from an uneven road surface, greatly shorten the lifespan of Campagnolo products, especially if your bicycle is equipped with tires, wheels, or stiff frames that are poor at absorbing shocks and vibrations.
The weight of the rider, type of bike and the style and conditions of use are all critical factors affecting the lifespan of your product.
Technical knowledge, experience, common sense, and prudence are required. If you weigh 80 kg or more, you must be especially vigilant and have your bicycle inspected regularly for any evidence of cracks, deformation, or other signs of fatigue or stress. Check with your mechanic to discuss whether the components you selected are suitable for your use, and to determine the frequency of inspections."

Quote:

Originally Posted by dookie (Post 6023866)

more CYA legalese...doesn't mean they break at 190.

While it may be a bit of CYA, the fact that they publish a number for Titanium and not for the SS or Cromo models would represent some type of limitation.

Quote:

Originally Posted by dobber (Post 6024054)

While it may be a bit of CYA, the fact that they publish a number for Titanium and not for the SS or Cromo models would represent some type of limitation.

What is "SS"? What material does it denote, in this case?

Titanium is in all aspects stronger, harder, stiffer than aluminum. It's somewhat heavier, but not much. And it's much more expensive. Otherwise it is the perfect metal for almost all things bicycle, eccept the chain (and chainrings, if you are anal about durability like I am).

Quote:

Originally Posted by wroomwroomoops (Post 6024118)

What is "SS"? What material does it denote, in this case?

Stainless Steel? It's pretty common.

single speed! er...stainless steel.

aw.. yeah, alright. Yes, steel in general has better characteristics than titanium. Except weight/density.

too bad they only made their seat post out of titanium and not the clamp.

Take a look at that stress fracture in the aluminum near the break, there is a discoloration in there that indicates that it had been cracked for a little while now, and then finally gave.

By the look of the design, I bet tightening torque is important on the bolts. They force the underside of the seatpost head against the protrusions that are missing, yes? So severe overtightening might put more force on them than spec'd... leading to a break. Not saying the OP did so, just sayin' it looks like a possibility with that particular design.

Quote:

Originally Posted by wroomwroomoops (Post 6022894)

Just to state the facts: nothing wrong with Titanium - it's a very strong metal, in all senses. Very reliable if welded properly.

What you had is the alloy part that failed.

Yup, totally true. I'm not dissing titanium as a material--heck the tube is fine. It's the unthinkably sh1tty engineering of the alloy clamp. In retrospect, it's hard to imagine a worse design. I wonder if anyone bothered testing this thing before shoving it out the door.

From the posting in the roadie forum it seems I'm not alone.

Quote:

Originally Posted by mconlonx (Post 6024549)

I would agree with this, but I hope you agree it's a poor design.

Quote:

Originally Posted by mconlonx (Post 6024549)

By the look of the design, I bet tightening torque is important on the bolts.

can't be! are you suggesting a torque wrench might have been appropriate?

(albeit still a sh|tty clamp design)

what caused the bruise on ur leg?

Quote:

Originally Posted by dobber (Post 6023158)

Aren't there some weight limitations often associated with titanium parts.

USE's website states, "We do not publish the maximum weight limits for our rigid seat posts. A light clumsy rider will do more damage to a seat post, than a heavier careful rider." Yeah, thanks chumps.

I told USE that I'm a reasonably skinny-ass rider (6' 170lbs) so weight wasn't a factor in their product's failure.
Besides, 75% of my body mass is contained by my massive quads anyway (obviously) which is mostly borne by my cranks. ;)

sort of like this guy:
http://i2.photobucket.com/albums/y44...lleville03.jpg

the good thing about being a clyde, is not trusting anything that doesn't look nuke proof.

the first time I saw that type clamp, I envisioned pain.