Duraace crank unusual crack



enegret

New Member
May 30, 2010
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Hi:

I recently upgrade my scott speedster S50 from shimano sora components to a shimano duraace - ultegra mix. From the moment I installed the duraace crank, i had a strange clicking noise coming from the crank. It clicked only when aplying a lot of force, that is while riding standing up, on the small front cog and on the 3-4 biggest rear cogs, only on steep hills. I isolated the noise only to the drive side, as pedaling only aplying force on the left side would eliminate the noise completely, doing the oposite would increase the noise.

I greased everything on install, checked chainring bolts, bb cups, etc and couldnt get the noise off...

Today i came back home from my mothers house, I had left the bike upside down as I took my recently build rear wheel for some touch-up truing, sat on the chair, and noticed a nice-ass CRACK on the rear of the crank!!!

It only has 296 km (185 miles for the non-IS). I bought it like one year ago, was the first part I bought for the upgrade. But Dura-ace has a 3 year warranty, so im taking it back to the shop. Being Chile, it will probably end in the shops trash, but being a mechanical engineering student, i would like to hear about this from shimano. Anyone knows how to contact shimano directly? And who to contact for a south america sold component? they have no email!

I looked for other crank failures, but i found none of this kind. Anyone seen some thing like this before?

Sorry if my english is bad, have not written in english in a long time.

Have a nice day, Esteban

Here goes the pictures:

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tafi

Active Member
Jul 31, 2003
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Classic fatigue crack.

Never seen that before but the crack is at least in an area where you would most expect it (at the base of the crank arm where stresses and stress concentrations are highest).

My guess is that the crank would have been flawed/damaged before use.

I don't think that is a piece that can be repaired. Welding aluminium is a specialist job and would leve a massive heat affected zone. The problem would just come back meaner and angrier next time. It's for the bin.

Shimano probably also won't let you keep it anyway since they will want to minimise liability.
 

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