Cracked 7800 crankarm.

[Matthew]

While on a group ride this evening I had just pulled off the front and was easing my way to the back of the line when I stood up briefly to stretch and catch back on and snap, my left crankarm cracks and folds inward a half inch or so. Fortunately it did not shear off and I did not crash but needless to say it put and end to my group ride. I was able to push it back kind of straight as to avoid the chainstay and limp back home. It nicked up a decal but otherwise did no damage to the stay (titanium). So glad I was not still on the front as that could have been disasterous. It was a Dura Ace 7800 crankarm and I thought it was in great shape, no nicks or scratches really. In fact I can't see any marks near the crack at all. Never expected that to happen. Scary. Anyone have a 7800 left crankarm (170mm) for cheap?? Hate to have to buy a new crankset. Matthew.

[Louis]

If you have a camera with a good macro lens post pictures of both sides of the failure surface. It might be interesting - many times you can see two distinct propagation modes, the long-term fatigue crack growth, and when the total area was too small, the near-instantaneous final static overload.

[Peter P.]

You may not have to buy a new crankset.

I was able to order a replacement left arm only for my old 6400 series Ultegra crank, which was damaged in a car accident. My local bike shop ordered and it arrived in a week.

[Stephen2014]

Did it crack at the crank eye, the most usual place? The direction of the pedal thread means on the left side they can tighten over time and cause pressure.

[djg21]

I had one crack years ago where it had gotten scored by rubbing against the front derailleur.

[Matthew]

It cracked about an inch or so above the pedal hole.

[oldpotatoe]

It cracked about an inch or so above the pedal hole.

Call shimano, ya never know. Broken crank arms, even the Hollow ones, are very rare.

[Cicli]

Call shimano, ya never know. Broken crank arms, even the Hollow ones, are very rare.

Agreed, Shimano may want to look at that.
Glad you were not hurt.

[dvs cycles]

A buddy had his break right at the pedal threads just as he was taking off from a stop. Luckily did not go down but left stranded while his girlfriend went back to get the car.
For sometime before that he had been searching for a new noise.
FOUND IT.:eek:

[Matthew]

Took it to my shop today. He made it sound as if it was somewhat common. Got the: Well naturally it happened, it's a Shimano product. "Their crankarms are hollow." He of course is a big supporter of Sram stuff. Whatever. Anyway he took pictures of it and was going to call Shimano today and send the photos. Have not heard back from him yet. He said it is possible they could send me a new arm but I don't expect that really. Matthew.

[thirdgenbird]

I saw a thread on another forum where there were a few examples of cracked 7800 cranksets. Some at the spider, some at the pedal hole, and others in the middle of the arm.

[Team Murray]

Tell you what. For the price of shipping, I will give you a set of 7800 cranks in 172.5. I have no need for then. They have a little surface rust on the axle.

[apeescape]

Any shop who prefers SRAM opposed to Shimano (road stuff) I would seriously question anything else they said...

[rwsaunders]

Tell you what. For the price of shipping, I will give you a set of 7800 cranks in 172.5. I have no need for then. They have a little surface rust on the axle.

+1...class move.

[endosch2]

This happened to a friend of mine on a dura ace crank last year on a group ride. Sheared off on the rh about an inch above the spindle. Not to start a war, but has anyone ever seen a carbon Campy crank break?

[thirdgenbird]

I've seen a picture of a broken ultra torque spindle but no explanation. It could have been hit by a car. No broken carbon crank arms. That said, I'm not sure I've ever seen a broken shimano crankset that wasn't 7800.

[oldpotatoe]

Took it to my shop today. He made it sound as if it was somewhat common. Got the: Well naturally it happened, it's a Shimano product. "Their crankarms are hollow." He of course is a big supporter of Sram stuff. Whatever. Anyway he took pictures of it and was going to call Shimano today and send the photos. Have not heard back from him yet. He said it is possible they could send me a new arm but I don't expect that really. Matthew.

He must be very familiar with calling a manufacturer about broken 'things' then..