Rotor 3DF failure

Discuss light weight issues concerning road bikes & parts.
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Joined: Thu May 01, 2008 8:51 pm
Location: France

by maquisard

Riding along today in the wet and crack, got up out of the saddle to sprint and my Rotor 3DF crank cracked and broke at the threads. I was left with the remainder of the right crank still attached to the pedal and I was left to ride home one legged.

Looking at both ends of the break, one side is clean metal, the other side looks corroded like there has been a crack in the metal or an imperfection in the metal at time of forging.

Was lucky to stay up right and the jagged end of the crank cut my overshoe and leg! Thanks Rotor!




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by RichieE46

Wow that sucks! Glad you're alright overall.

I wonder if Rotor will take care of you on the crank.

by Weenie

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Joined: Tue Oct 04, 2011 9:16 pm

by trilocus

I had a problem with a rotor 3d crankset, and rotor changed me the crankset very fast. But i am from Spain i don't if in another country works like in spain

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by tinozee

Woah scary. Nice job surviving that.

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by 2tonGorilla


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by Zigmeister

Yeah, I would be contacting Rotor about that one....

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by victorduraace

You could as well be now in ICU unconscious... You are very lucky, just like me when crank broke I stayed upright...
How fast were You going?
Rotor has nice warranty service though...

Posts: 1818
Joined: Thu May 01, 2008 8:51 pm
Location: France

by maquisard

It was along a main road in rural France. I got out of the saddle to sprint over a little bump and my right foot came free. At first I thought I had broken my cleat or pedal, but quickly realised I would have to ride home with one leg! Annoyingly I tore up a new pair of overshoes that were on their first ride.

Hopefully Rotor will replace it under warranty. I will try to upgrade to a 3D+ over a 3DF as I don't have much faith in the forging process after this!

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Joined: Wed Oct 23, 2013 9:55 pm

by Qman

Looks like a fatigue failure. In the second photo on the right hand side at the bottom by the threads is where the crack started. You can see the bands radiating out from that point. That shows how the crack grew. Then the bands stop and the surface becomes rough. That is the final bit of metal that was hanging on before it suddenly broke. The crack was there for a while, slowly growing each time you pedalled. Usually these things start from a small imperfection in the surface. It could have been there from the factory, or it could have been damaged sometime later. Hopefully you get it covered under warranty!

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Location: Seattle

by rebizap

Do you have picture of the side of the crank arm?

Whats on the side of the crank arm in the last pic?

Has it been crashed on before this incident?

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Joined: Thu Apr 11, 2013 2:50 am

by g32ecs

OP sent me his pic


I always think ppl who break cranks have Hulk-like power.

Posts: 1818
Joined: Thu May 01, 2008 8:51 pm
Location: France

by maquisard

I wish!

Posts: 1818
Joined: Thu May 01, 2008 8:51 pm
Location: France

by maquisard

Happy to report that Rotor replaced my 3DF crank and spider with a brand new one immediately no questions asked.

In the interim I upgraded to a 3D+ so now have a brand new in box BB30/BBright 110BCD 175mm to sell if anyone is interested.

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Location: London

by DWatkinsBSB

Great that Rotor got you a new crank, but did they mention anything with regards to your failure? That sort of failure does concern any potential new buyers and makes me think twice before going for a rotor crank...

by Weenie

Posts: 1818
Joined: Thu May 01, 2008 8:51 pm
Location: France

by maquisard

No, nothing mentioned with regards to the cause. They just supplied me with a new crankset without asking for anymore description of the events when it failed.

Unless it happens regularly, which a quick trip to google reveals it doesn't, I wouldn't worry. It was probably just an inperfection in the forging process or an issue when the threads were tapped in the crank.

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