Broken Crankarm
#1
Broken Crankarm
Look at what I did. I was accelerating out of a track stand in the middle of a busy intersection, I ate total $#@t. The crank is stock on a 2003 specialized langster. Do you think this result of a crappy part or my superhuman strength? (any suggestions for a new crank would be much appriciated)
#2
Nothing lasts forever.
Here is my limited knowledge classical explanation of what probably happened to your crank:
A crack started somewhere in the upper left hand corner of the broken cross-section in the 2nd picture. This crack was present for a long time. It grew and grew over a period of weeks. You can tell because that area is discolored from oxidation and microscopic crud as the crack moved slightly and admitted the outside atmosphere.
One day, at the worst possible time, the crack reached some critical length and broke apart entirely in one instant.
What can you do to avoid this?
Nothing. It is the failure mode of aluminum. The only thing you can do is to inspect your cranks regularly (once a month or so). These cracks grow slowly at first, so you have a chance to catch them if you keep everything clean and look closely. Also, be sure to track down the cause of any squeaks and creaks on your bike-- it could be a crack!
Here is my limited knowledge classical explanation of what probably happened to your crank:
A crack started somewhere in the upper left hand corner of the broken cross-section in the 2nd picture. This crack was present for a long time. It grew and grew over a period of weeks. You can tell because that area is discolored from oxidation and microscopic crud as the crack moved slightly and admitted the outside atmosphere.
One day, at the worst possible time, the crack reached some critical length and broke apart entirely in one instant.
What can you do to avoid this?
Nothing. It is the failure mode of aluminum. The only thing you can do is to inspect your cranks regularly (once a month or so). These cracks grow slowly at first, so you have a chance to catch them if you keep everything clean and look closely. Also, be sure to track down the cause of any squeaks and creaks on your bike-- it could be a crack!
#3
Also, be sure to track down the cause of any squeaks and creaks on your bike-- it could be a crack!
#6
mountain troll
Joined: Sep 2004
Posts: 1,127
Likes: 0
From: santa cruz mountains
Bikes: the hummer brand mountain bike
one time a broke a crank on my schwinn road bike 2 years ago... was in an intersection and stood up to accelerate and bam i ate total ****, my balls met the top tube and everyone driving their cars could give a **** about my body sprawled on the ground lol.
i say it's superhuman strength, we are genetic freaks of the bicycle
i say it's superhuman strength, we are genetic freaks of the bicycle
#7
I have crashed recently, but I laid it down on the left side. Aside from that, the bike goes through hell on a weekly basis. I'm kind of glad it happened though, nothing like an excuse to upgrade.
(anybody have any recomendations for a new crank set, I was looking at the miches but I heard that they have a proprietary bcd, and you can only use miche chainrings.)
(anybody have any recomendations for a new crank set, I was looking at the miches but I heard that they have a proprietary bcd, and you can only use miche chainrings.)
#8
yeah, miche is 135mm BCD, which is the Campy road standard. So they're not really "proprietary" per se.
If you want 1/8" rings for your miche cranks, you're limited to Miche and TA, I believe. But if you're happy with 3/32" then you have more choices.
If you want 1/8" rings for your miche cranks, you're limited to Miche and TA, I believe. But if you're happy with 3/32" then you have more choices.
#11
knucklehead
Joined: Feb 2005
Posts: 520
Likes: 0
From: East Village, NYC
Bikes: Rocky MT Track, Vivalo, Pista Concept, De Bernardi Track
Originally Posted by pwarre20
I have crashed recently, but I laid it down on the left side. Aside from that, the bike goes through hell on a weekly basis. I'm kind of glad it happened though, nothing like an excuse to upgrade.
(anybody have any recomendations for a new crank set, I was looking at the miches but I heard that they have a proprietary bcd, and you can only use miche chainrings.)
(anybody have any recomendations for a new crank set, I was looking at the miches but I heard that they have a proprietary bcd, and you can only use miche chainrings.)
#12
LF for the accentdeprived
Joined: May 2005
Posts: 3,549
Likes: 0
From: Budapest, Hungary
That's a Specialized crank, isn't it? It really shouldn't break unless it is crashed, IMHO. Even if you rode it aggressively, skidding and all that, and you weigh 200 pounds, a crank mustn't crack like that.
Whatever... Maybe drop a line to Specialized... Not really a warranty issue as it's 2 years old, but at least they'll know they're makin crap.
Whatever... Maybe drop a line to Specialized... Not really a warranty issue as it's 2 years old, but at least they'll know they're makin crap.
#13
Rebel Thousandaire
Joined: Sep 2004
Posts: 733
Likes: 1
From: Hartford, CT
Bikes: Public D8, Yuba Mundo (cargo), Novara Buzz (1-speed, soon to be 2-speed w/ a kickback hub), Xootr 1-speed folder
Everyone here seems to think there was a manufactuing flaw or a hairline fracture, but I think, after getting in this miserable and silly accident, you deserve to be told something nicer: It obviously happened because you are super duper strong. Have your next crank made from cast iron.
#14
Get the stick.
Joined: Nov 2004
Posts: 1,543
Likes: 1
From: Toronto, ON
Bikes: 12 Y.O. Litespeed MTB, IRO Jamie Roy fixie, Custom Habanero Ti 'Cross, No name SS MTB, Old school lugged steel track bike (soon)
Looks like a cheesy cast crank to me. See if you can replace it with a forged crank.






