shredded crank -

[shorty]

middle of a race today - i stood up to sprint

my right pedal ripped out of crank thread taking part of the "threaded insert". i stayed upright as did those behind me - lucky

an expensive mechanical
carbon record cranks - 2 years old 15000 km - wrecked
look keo pedal - new - ok

anyone hear of this happening before ?

flaw in crank insert or pedal problem ?


appreciate the input before i decide on what to buy as a replacement.

thanks

 

[Chuck731]

What crank is it? Not Campy Record, I hope.

 

[shorty]

yep

campy

disaster

 

[531Aussie]

sorry to be a smartarse, but: carbon cranks? no wonder.

It's only anecdotal, but I've heard this before

 

[shorty]

sorry to be a smartarse, but: carbon cranks? no wonder.

It's only anecdotal, but I've heard this before

well i thought the same until discussed with a knowledgeable friend. he says its irrelevant - in this case. carbon or alloy. there is the same threaded steel insert in both - it is this part that failed. cracked. 1/2 left on my pedal and half left inside carbon crankarm.


so sorry to be smart **** but sounds like you may be wrong - the carbon was stronger than the steel - in this case

what would cause the steel insert to fail...pedal tightness a therory ?

interested to hear other opinions

 

[rek]

I've heard of Raceface and Truvativ freeride/downhill cranks suffering from the same fate (the threaded pedal inserts failing).

Strange to hear of a road crank doing the same though, you wouldn't think they'd have to cop anywhere near as much abuse as extreme MTB bits..

 

[dhk]

well i thought the same until discussed with a knowledgeable friend. he says its irrelevant - in this case. carbon or alloy. there is the same threaded steel insert in both - it is this part that failed. cracked. 1/2 left on my pedal and half left inside carbon crankarm.


so sorry to be smart **** but sounds like you may be wrong - the carbon was stronger than the steel - in this case

what would cause the steel insert to fail...pedal tightness a therory ?

interested to hear other opinions

From your description, it sounds like my Speedplay pedals and FSA Team Carbon crank, where the pedal threads only reach about halfway into the threaded insert.
It's great to save weight on pedals for marketing purposes, but for strength, full thread engagement at this highly-loaded point would be much better. On my FSA crank, believe the inserts are aluminum, not steel, which doesn't make them stronger.

Suppose it's possible that the pedal was overtorqued, causing the insert bond to partially fail due to the high torque, setting you up for the break. Another posibility is that the bond loosened due to a previous crash or fall. Of course, it could just be a manufacturing defect as well.....no one, even Campy is immune from those.

Does the bore of the CF arm look enlarged, like the insert was wallowing around in the CF bore before it broke, or does it appear the insert just pulled out?

Would be interesting to know if Campy has any notes or warnings about pedal thread engagement, or specifies certain brands of pedals to avoid because of their limited thread engagement. Wonder if Record pedals have deeper threads than the Keo?

Sorry I've got more questions than answers here.

 

[alienator]

sorry to be a smartarse, but: carbon cranks? no wonder.

It's only anecdotal, but I've heard this before

Yeah, I have, too, except what I heard was about internet myth mongers and people who can't wrap their brains around proper design jumping to conclusions about Material X, as if the material something is made of tells you everything about that part.

Try using the critical thought thing: you'll get farther in life.

 

[artmichalek]

Would be interesting to know if Campy has any notes or warnings about pedal thread engagement, or specifies certain brands of pedals to avoid because of their limited thread engagement. Wonder if Record pedals have deeper threads than the Keo?

Along with the standard "serious injury or death" statement, they give dimensions for minimum contact area of the pedal spindle. The pedal should thread at least 11.7mm into the crank.

http://www.campagnolo.com/pdf/7225254_Crankset.pdf

Note that it's the same manual/warning for both carbon and alloy cranks.

 

[Adam-from-SLO]

yep

campy

disaster

Just curious, but was this Campy Carbon crank the origional Carbon that came out in 2003(I think).... or is it the newer Multi-directional Carbon Crankset ?

 

[dhk]

Along with the standard "serious injury or death" statement, they give dimensions for minimum contact area of the pedal spindle. The pedal should thread at least 11.7mm into the crank.

http://www.campagnolo.com/pdf/7225254_Crankset.pdf

Note that it's the same manual/warning for both carbon and alloy cranks.

Art, nothing like some real data, thanks. My Speedplay Zero's are right around this minimum dimension as well....just measured them at 12 mm, with 4 mm of threads showing on the back side of the FSA crankarm. I'd prefer having a full 16 mm of thread, but suppose it's just one of the compromises we make to save grams.

 

[shorty]

Art, nothing like some real data, thanks. My Speedplay Zero's are right around this minimum dimension as well....just measured them at 12 mm, with 4 mm of threads showing on the back side of the FSA crankarm. I'd prefer having a full 16 mm of thread, but suppose it's just one of the compromises we make to save grams.

thanks all so far. i measured Look Keo thread - 12mm too. i went and measured a pair of old heavy Look "clunkers" from 5 or 6 years ago. same 12 mm.

so i guess its not a new weight saving issue there. i agree though...would prefer a few mm extra to avoid possibility of it casuing a problem.

The cranks were 2004 model...after they had changed them. i dont think they have changed the arms since. the chainrings have been "improved" 06 though.

on issue of over torqueing or tightening. i can confidently say i hadnt done that. the look keo use an allen key. you cant use a big spanner so hard to overtighten. my concern was with under tightening ? but mate at LBS says as long as you tighten up then give a wee tweek....they are tight enough.

looking at the cracked threaded insert that came out of crank attached to pedal. its probably alloy not steel as i previously thought. held in place by glue ? !! it has shattered "like a rotten tooth" - im thinking an over torqueing of a previous pedal would have caused a weakness. that theory makes sence. an over zealous mechanic and a big spanner can do alot of damage.

either that or a manufacturing defect - you would have though we would have heard of more instances ?

have been told it is a warranty issue, Campag will replace. but im out of warranty !

cheers again

 

[dhk]

Thanks for the reply. I'm wondering if the original pedals were overtightened, or siezed onto the arm due to corrosion, and took a lot of torque to remove? If so, perhaps some damage occurred to the insert then. How long had the Keo pedals been on before you had the failure?

Could there have been some crash or other damage where the pedal took a good hit? On the other hand, maybe the bond was poor, a rare manufacturing defect.

Suppose it doesn't matter now. The good thing is you weren't hurt, or didn't cause a big pileup....the crankset just takes money (OK, a lot of money) to replace.

 

[shorty]

Thanks for the reply. I'm wondering if the original pedals were overtightened, or siezed onto the arm due to corrosion, and took a lot of torque to remove? If so, perhaps some damage occurred to the insert then. How long had the Keo pedals been on before you had the failure?

Could there have been some crash or other damage where the pedal took a good hit? On the other hand, maybe the bond was poor, a rare manufacturing defect.

Suppose it doesn't matter now. The good thing is you weren't hurt, or didn't cause a big pileup....the crankset just takes money (OK, a lot of money) to replace.

the Keo pedals are pretty new. perhaps 10 rides. 6 races. id had them on and off a few times as i use them on my track bike. never overtight.


im tipping it was on previous pedals. i bought these cranks off a friend when he went to compact cranks. 3 months ago. he looked after his gear. i rode with him. he was a lightweight and did not race- had not crashed them.

im in agreement. no one was hurt. its not all bad. i did not pay big bucks anyway.

i have also just had a call from LBS. 3 year warranty and campag are likely to replace. they want to look at them. im just worried about left crank now. is it ready to go ?...i might push for replacement of both.

 

[dhk]

the Keo pedals are pretty new. perhaps 10 rides. 6 races. id had them on and off a few times as i use them on my track bike. never overtight.


im tipping it was on previous pedals. i bought these cranks off a friend when he went to compact cranks. 3 months ago. he looked after his gear. i rode with him. he was a lightweight and did not race- had not crashed them.

im in agreement. no one was hurt. its not all bad. i did not pay big bucks anyway.

i have also just had a call from LBS. 3 year warranty and campag are likely to replace. they want to look at them. im just worried about left crank now. is it ready to go ?...i might push for replacement of both.

That sounds like a fine offer from Campagnolo, considering you are not the original purchaser. It's good they want to get the failed item back for analysis; says a lot about the company to me.

It does seem smart to replace both crankarms now. Suppose it can't hurt to ask for free replacement of the left, but believe I'd do it even if I had to pay something.

 

[531Aussie]

Yeah, I have, too, except what I heard was about internet myth mongers and people who can't wrap their brains around proper design jumping to conclusions about Material X, as if the material something is made of tells you everything about that part.Try using the critical thought thing: you'll get farther in life.

Dude ......I was talking about what I've heard and SEEN at my bike club and my regular bike shops, not the net.

Are you gunna tell me that carbon doesn't have it's problems? What about the seatpost 'situation'? You can't tell me you don't know of carbon posts breaking, but have you heard of alu seatposts snapping? I haven't.

Once again (as I said), this is only anecdotal, but I know of a handful of brand new crabon cranks busting, but the busted alu cranks I've seen are usually older than 10 years.

Don't worry, you're $1000 carbon cranks probably won't break......or will they?

 

[alienator]

Dude ......I was talking about what I've heard and SEEN at my bike club and my regular bike shops, not the net.

Are you gunna tell me that carbon doesn't have it's problems? What about the seatpost 'situation'? You can't tell me you don't know of carbon posts breaking, but have you heard of alu seatposts snapping? I haven't.

Carbon fiber doesn't have a problem. People that don't design for its use properly have the problem. I understand that you have zero technical background, but still, it's been said enough that you should have heard it: a material, alone, tells you nothing about a product. Zippo. Whether a product works or fails is dependent on proper care, proper design, proper construction techniques. And yes I've heard of Al posts failing. In fact, this summer I saw an Al post fail underneath a rider in front of me. Saying CF has big problems and just isn't as good as this or that. just because it's CF is ignorant at best.

Once again (as I said), this is only anecdotal, but I know of a handful of brand new crabon cranks busting, but the busted alu cranks I've seen are usually older than 10 years.

But we should take your word on that, right? I mean you've got the technical wherewithal to make the final judgement on CF, right?

Don't worry, you're $1000 carbon cranks probably won't break......or will they?

$1000? Really? I didn't know that I had that much money to throw at cranks. You should try learning about materials and engineering so that you don't end up looking like the kid in the corner wearing the dunce cap.

 

[Postie]

Carbon fiber doesn't have a problem. People that don't design for its use properly have the problem. I understand that you have zero technical background, but still, it's been said enough that you should have heard it: a material, alone, tells you nothing about a product. Zippo. Whether a product works or fails is dependent on proper care, proper design, proper construction techniques.

You're statement isn't correct. I'll agree that there are a lot of good safe carbon products out there and I'll also agree that "well engineered by credible manufacturers" vs "poorly engineered parts" means more then simply looking at the material the parts are made of. However, there is a point of which amount of force applied to any material causes that material to alter it's current shape. That amount of force is different for each product made so it's very possible to have an instance of a carbon part that is 5 times stronger then a similar aluminum part.

However the difference is what happens when the material is put under stress greater then the point that causes the it to compromise it's current shape. When this happens to aluminum, the aluminum usually bends. When this happens to carbon, carbon snaps in half. This is due to the material and not on the construction.

What manufacturers are doing is making some carbon parts up to 10x stronger then their equivalent aluminum parts so that they can claim that nothing reasonable should compromise their integrity. However, the fact remains, if something happens to the carbon part, it's probably snapping in half. And when it comes to seat posts, I'd much rather have one bend.

Clearly though, this has nothing to do with the problem with the "shredded cranks".

 

[531Aussie]

You should try learning about materials and engineering so that you don't end up looking like the kid in the corner wearing the dunce cap.

OOOOH....ZING!! you need better writers

Hmmmm, let's see; you patronise me, virtually saying I don't know anything, then imply that I'm ignorant and a dunce. I won't be doing that.

I obviously can't tell you you didn't see an alu post fail, but I've been riding and hanging out at bike shops (too much) for 20 years, and I've never heard of an alu road post breaking. I've seen a couple on BMX jump bikes busted.

It dosen't matter why some carbon breaks, whether it's poor design or people buy the 'wrong' brand, or whatever, the fact is there's more carbon stuff breaking out there than alu, and if you challenge that, even with my lack of empirical references, you'll be deluding yourself. You wouldn't catch me using carbon cranks, posts or stems, and I even swap my carbon forks every couple of years. If there were a decent range of quality alu forks out there I'd get some.


by the way $1192 AUS for Campag Carbon cranks. What a ripoff!!! http://www.cecilwalker.com.au/category148_1.htm

 

[Adam-from-SLO]

However, there is a point of which amount of force applied to any material causes that material to alter it's current shape. That amount of force is different for each product made so it's very possible to have an instance of a carbon part that is 5 times stronger then a similar aluminum part.

Ahhhhhh , May the Force be with you.... always