Snapping Crank Axle! Unheard off!

[le_quiet_uno]

Hi all,

I have heard many of riders snapping chain but have never heard of anyone snapping a crank axle!

I have been riding a little and have done most of my riding up and down Bobbin Head, Galston, Berowera...etc.

After a ride from Greenacre down to Waterfall and up Audley on Sunday, thought a nice relaxing ride down La Perouse. Half way into the ride, the crank axle snapped clean!











Has anyone experienced this?? What could be the cause of it? And is it repairable?

Your feedback would be appreciated!


Cheers,
LQU

[zero]

Repair is most likely to replace the crankset - I don't know how the halves are attached to the arms.

The likely cause is that the hirst joint bolt was loose - judging by the fretting of the joint. One imagines that once its loose and allowed to fret it is probably a risk of breaking the bolt, as that will transfer load from the joint to the bolt. (the broken thing in the picture is the bolt).

I think its a rare failure, put down to no-one ever checking it properly.

[uncle arthur]

Looks like your internal tubemounted electric assist crank motor might be rubbing on your crank bolt (those drive teeth are very dirty).

Seriously, any metal part can fatigue and break - and your existing crank is probably not repairable, but certainly replaceable.

[zero]

May even be possible to repair if the old bolt is extractable from both halves. Hirst joints are supposed to be fairly tolerant of minor damage.

[ldrcycles]

Not unheard of, but not common, and not fun. This is the first Campagnolo one i've seen though.

[open roader]

From the images provided it appears the internal Ultra Torque bolt that holds the two crank sides together has been sheared. It may have been over torqued and fatigued. If you can extract the sheared bolt section out of the two crank halves and the threads are intact then you simply replace the bolt as the splines look perfect (at least the ones I can see in the pics)

[le_quiet_uno]

Repair is most likely to replace the crankset - I don't know how the halves are attached to the arms.

The likely cause is that the hirst joint bolt was loose - judging by the fretting of the joint. One imagines that once its loose and allowed to fret it is probably a risk of breaking the bolt, as that will transfer load from the joint to the bolt. (the broken thing in the picture is the bolt).

I think its a rare failure, put down to no-one ever checking it properly.

Hi Zero,

Thanks for your feedback. The bike was taken to the bike shop for a total overhaul when I got it. Would it be a possibility that it was an oversight by the mechanic?

[le_quiet_uno]

Looks like your internal tubemounted electric assist crank motor might be rubbing on your crank bolt (those drive teeth are very dirty).

Seriously, any metal part can fatigue and break - and your existing crank is probably not repairable, but certainly replaceable.

Hi Uncle Arthur, sorry, I pretty much got metal fatigue. Does this mean that a brand new crankset is required?

[le_quiet_uno]

May even be possible to repair if the old bolt is extractable from both halves. Hirst joints are supposed to be fairly tolerant of minor damage.

Hi Zero,

Not so sure if it is extractable as it doesn't leave much space for the mechanic to hold onto. But will check with the guys in the shop tomorrow.

[le_quiet_uno]

Not unheard of, but not common, and not fun. This is the first Campagnolo one i've seen though.

It sure wasn't fun. Luckily I had a mate with me at the time so I could use his bike to get my car to pick everything up.

[le_quiet_uno]

From the images provided it appears the internal Ultra Torque bolt that holds the two crank sides together has been sheared. It may have been over torqued and fatigued. If you can extract the sheared bolt section out of the two crank halves and the threads are intact then you simply replace the bolt as the splines look perfect (at least the ones I can see in the pics)

Hi Open Roader,

That is something I will need to check with the shop tomorrow. I can't see how the metal can fatigue when the total km of the groupset has done roughly 7000km with a major overhaul in April this year. :S

[open roader]

My bet is that you can fix this for the cost of a new Ultra Torque bolt. If the bike shop says they want to sell you a new crank set then go elsewhere as I'm 99% sure I could fix this one myself.

It's easy to overtorque a bolt like this and re-checking the torque level is perhaps not on the highest priority of a shop mechanic when he/she is performing a once over for a 2nd hand purchase. purchase.

[zero]

From the images provided it appears the internal Ultra Torque bolt that holds the two crank sides together has been sheared. It may have been over torqued and fatigued. If you can extract the sheared bolt section out of the two crank halves and the threads are intact then you simply replace the bolt as the splines look perfect (at least the ones I can see in the pics)

Hi Open Roader,

That is something I will need to check with the shop tomorrow. I can't see how the metal can fatigue when the total km of the groupset has done roughly 7000km with a major overhaul in April this year. :S

If you stress steel below 50% of yield, it will usually do many millions of cycles between failures. if you stress it well past 50% of yield, then it can fail in thousands of cycles.

having read around, there is a clip that can be had to stop the whole thing falling out if it fails, and overtorque failures are supposed to be uncommon but fairly common amongst the hamfisted owners without torque wrenches.

I'll go with open roaders answer and hopefully it should be cheap. That half of the bolt looks easily removed as it still has its square surfaces.

[le_quiet_uno]

My bet is that you can fix this for the cost of a new Ultra Torque bolt. If the bike shop says they want to sell you a new crank set then go elsewhere as I'm 99% sure I could fix this one myself.

It's easy to overtorque a bolt like this and re-checking the torque level is perhaps not on the highest priority of a shop mechanic when he/she is performing a once over for a 2nd hand purchase. purchase.

Hi Open Roader,

Thanks for your advice! Like you said, the shop was going to get me a new crank but when I was about to walk out they mentioned that they could fix it.

But they have no idea how much it would cost as they don't have the part and will need to order it in.

I would have thought that they will pay a lot more attention considering I ask for a full service which they charged me a pretty penny.

[le_quiet_uno]

From the images provided it appears the internal Ultra Torque bolt that holds the two crank sides together has been sheared. It may have been over torqued and fatigued. If you can extract the sheared bolt section out of the two crank halves and the threads are intact then you simply replace the bolt as the splines look perfect (at least the ones I can see in the pics)

Hi Open Roader,

S

If you stress steel below 50% of yield, it will usually do many millions of cycles between failures. if you stress it well past 50% of yield, then it can fail in thousands of cycles.

having read around, there is a clip that can be had to stop the whole thing falling out if it fails, and overtorque failures are supposed to be uncommon but fairly common amongst the hamfisted owners without torque wrenches.

I'll go with open roaders answer and hopefully it should be cheap. That half of the bolt looks easily removed as it still has its square surfaces.

Hi Zero,

I don't work on my bike with the exception of general clean and maintenance as I don't have a torque wrench and knowing how easy to crack a road bike.

That's the reason I visit that shop on a regular basis for servicing and assembly.

[open roader]

Ham fisted owners sans torque wrenches or otherwise, this is a rare occurance in my books. If you can re-fit a new ultra torque bolt and you are guaranteed it's torqued to 40Nm then it's very unlikely to ever be an issue again.

[__PG__]

Two questions
1) The Crankset uses a 24 mm steel axle?
2) Did you crash? I imagine that the loss of balance could have been quite severe, especially if you were pushing a high gear.

It must have been amusing and alarming to have a crank dangling from your cleat!

[le_quiet_uno]

Ham fisted owners sans torque wrenches or otherwise, this is a rare occurance in my books. If you can re-fit a new ultra torque bolt and you are guaranteed it's torqued to 40Nm then it's very unlikely to ever be an issue again.

Hi Open Roader,

Went to the shop and they have confirmed that it must have been over tighten as the groupset has done no more than 7000km. Too early for the ultra torque bolt to fail.

They will re-check everything for me to make sure all bolts are torque to the right spec. Can't have bits and piece flying off during a decent down a hill.

[le_quiet_uno]

Two questions
1) The Crankset uses a 24 mm steel axle?
2) Did you crash? I imagine that the loss of balance could have been quite severe, especially if you were pushing a high gear.

It must have been amusing and alarming to have a crank dangling from your cleat!

Hi PG,

Am not sure the size of the bolt. Would assume they are just the standard size bolt.

Luckily the bolt snapped just before the climb. I think I almost soiled myself when I saw my left foot came flying out!

I think I yelled out a lot of things that I should not repeat here. But was lucky to be able to unclip my right foot to come to an stop.

[le_quiet_uno]

Hi all, many thanks for your input! Here are some new photos showing the snapped bolt:

[biker jk]

Perhaps not as rare as believed. A friend had the same problem.

[Nobody]

Shimano can have problems too if a bearing seizes.


viewtopic.php?f=34&t=40469

[biker jk]

Shimano can have problems too if a bearing seizes.

True but they are just a "fishing tackle" company dabbling in bike components while Campagnolo is supposed to be the Lamborghini of groupsets (hang on, didn't they start out making tractors?).