Crank Failure
03-22-15, 05:11 PM
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03-22-15, 06:18 PM
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I am beginning to think bad design. https://fcdn.mtbr.com/attachments/fat...lure-broke.jpgAustralian Cycling Forums - Broken Dura Ace 7900 Crankset
03-22-15, 08:15 PM
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I am beginning to think bad design. https://fcdn.mtbr.com/attachments/fat...lure-broke.jpgAustralian Cycling Forums - Broken Dura Ace 7900 Crankset
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03-22-15, 08:17 PM
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Yes, I am heavy, 230lbs. and am strong. I have broken frames, handle bars, spindles, seat posts, seats, axels. You name it, I have broken it. I have pulled front derailleurs out of frams. It does seem that the 2011 Dura Ace and XTR cranks have had issues. There are pictures of broken cranks on the web. The break is all in the same place. There also a picture that looks to be of a 2011 spindle and of a spindle possibly of a later crank which is noticeably thicker. It might have been an issue that was fixed quickly because it seems like the posts and pictures are in that 2011 time frame.
03-22-15, 08:37 PM
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I posted two. If you want to bother, there are many more. It also looks like Shimano changed the design slightly on the spindle. I have been riding long enough on the track and road to know that my demographic is not the group road equipment is designed for. I have steel bars on my track bike for a reason.
Last edited by colnago62; 03-22-15 at 08:41 PM.
03-22-15, 08:37 PM
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If you're pulling fd's out of frames there's some mechanic, or user error
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03-22-15, 08:37 PM
#33
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03-22-15, 08:42 PM
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Yes, pros are strong, so they do design for a certain amount of strength, but unlike prior years where stage race bikes had to be built tough, better engineering tools now allow bikes to be designed very close to the line. That means less surplus reserve of strength and toughness. Also Marketing is demanding new lighter stuff every year, and the industry model is now more like that of the electronics world.
As I said, that may not be a problem per se, but it does make many offerings unsuited for weekend warriors who may weigh more, or have more of a mashing than spinning pedaling style. It also means that the "best" bikes are less suited to high mileage, everyday, all weather use with minimal service. In dog terms, we've moved from tough mutts to high strung, delicate purebreds.
This wouldn't be a problem a all, if makers made a point to offer B tier bikes that aren't just last year's A bikes. Adding a few grams to a B-level crank spindle would add little cost, and prevent much of this kind of issue, I just don't see it happening now.
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03-23-15, 12:13 AM
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One of the problems (if it's fair to call it that) with modern high end road stuff is that it's designed around competitive racing. That means a design standard where 175#s is considered very heavy, and pedaling style is almost exclusively high rpm cadence, even when climbing.
Yes, pros are strong, so they do design for a certain amount of strength, but unlike prior years where stage race bikes had to be built tough, better engineering tools now allow bikes to be designed very close to the line. That means less surplus reserve of strength and toughness. Also Marketing is demanding new lighter stuff every year, and the industry model is now more like that of the electronics world.
As I said, that may not be a problem per se, but it does make many offerings unsuited for weekend warriors who may weigh more, or have more of a mashing than spinning pedaling style. It also means that the "best" bikes are less suited to high mileage, everyday, all weather use with minimal service. In dog terms, we've moved from tough mutts to high strung, delicate purebreds.
This wouldn't be a problem a all, if makers made a point to offer B tier bikes that aren't just last year's A bikes. Adding a few grams to a B-level crank spindle would add little cost, and prevent much of this kind of issue, I just don't see it happening now.
Yes, pros are strong, so they do design for a certain amount of strength, but unlike prior years where stage race bikes had to be built tough, better engineering tools now allow bikes to be designed very close to the line. That means less surplus reserve of strength and toughness. Also Marketing is demanding new lighter stuff every year, and the industry model is now more like that of the electronics world.
As I said, that may not be a problem per se, but it does make many offerings unsuited for weekend warriors who may weigh more, or have more of a mashing than spinning pedaling style. It also means that the "best" bikes are less suited to high mileage, everyday, all weather use with minimal service. In dog terms, we've moved from tough mutts to high strung, delicate purebreds.
This wouldn't be a problem a all, if makers made a point to offer B tier bikes that aren't just last year's A bikes. Adding a few grams to a B-level crank spindle would add little cost, and prevent much of this kind of issue, I just don't see it happening now.
An Ultegra crank would certainly be more than adequate for me. But the OP had chosen Dura-Ace.
In many cases, ultra-heavy people (300+ are naturally choosing MTBs, although not all do. But, there are the ones in the middle like the OP at 230 lbs... which a road bike should be able to handle.
I know all about standing torque. My driveway peaks at about 17%, which I hit with a top gearing of 41-19 (700c), but sometimes even higher gears, 41-17.
I don't know the exact force that gets applied to the pedals, but it is somewhat near (180 lbs weight + 10 to 20 lbs pulling on handlebars + 10 to 20 lbs pulling on opposite pedal). So, the drive pedal gets the equivalent of about 220 lbs.
The OP may well be able to mash with excess of 300 lbs into the driving pedal. He also has more weight to pull up the hills.
The 150 to 170 lb pro rider may never actually exceed their weight with driving force, and derives HP from lower force at higher cadences.
My guess, as the OP is already suspecting. Shimano comes out with the new latest and greatest. Distributes prototypes to their teams for a few months. If all checks out, they do a few last minute changes, then send them off to market. On the open market, riding styles not anticipated by the pros start finding additional flaws. Perhaps also fatigue catches up with time.
If the company gets a rash of warranty claims, they will go back and fix the problem as an interim release.
03-23-15, 06:46 AM
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You weigh 230lbs. You have a self proclaimed history of breaking just about every piece of a bicycle.
Yet you claim that the design of the Dura Ace spindle is defective because your's broke, and you can google some examples of others breaking.
It's likely as has already been said in this thread that yours broke due a manufacturing defect, with the help of your size.
The reason for the "Whoosh" is you completely missed my point, that designs have tradeoffs, and if you want very light components, there is going to be a tradeoff in durability.
Shimano could have spec'd the spindle in your crank to be 5 times as strong as it is, giving it greater margin for error from manufacturing imperfections.
But it would be heavier, and people including yourself, wouldn't buy them.
The tradeoff in making lighter parts is that they occassionally are going to fail, particularly when used by people at the end of the bell curve.
Yet you claim that the design of the Dura Ace spindle is defective because your's broke, and you can google some examples of others breaking.
It's likely as has already been said in this thread that yours broke due a manufacturing defect, with the help of your size.
The reason for the "Whoosh" is you completely missed my point, that designs have tradeoffs, and if you want very light components, there is going to be a tradeoff in durability.
Shimano could have spec'd the spindle in your crank to be 5 times as strong as it is, giving it greater margin for error from manufacturing imperfections.
But it would be heavier, and people including yourself, wouldn't buy them.
The tradeoff in making lighter parts is that they occassionally are going to fail, particularly when used by people at the end of the bell curve.
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You could get lost and die.
You could hit a tree and die.
OR YOU COULD STAY HOME AND FALL OFF THE COUCH AND DIE.
03-23-15, 07:08 AM
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Yes, I am heavy, 230lbs. and am strong. I have broken frames, handle bars, spindles, seat posts, seats, axels. You name it, I have broken it. I have pulled front derailleurs out of frams. It does seem that the 2011 Dura Ace and XTR cranks have had issues. There are pictures of broken cranks on the web. The break is all in the same place. There also a picture that looks to be of a 2011 spindle and of a spindle possibly of a later crank which is noticeably thicker. It might have been an issue that was fixed quickly because it seems like the posts and pictures are in that 2011 time frame.
All you can do is get another DA crank or equivalent and install it to spec and hope for the best. I haven't heard of any particular crank being stronger or weaker. You may want to try a Campy UT crank but no idea if it has more spindle strength than a DA crank. Possible that a 30mm spindle aka BB30 maybe stronger than a DA 24mm spindle but not necessarily so....wall thickness is less in 30mm BB30 designs. Hope you get a replacement and glad you weren't hurt.
03-23-15, 07:25 AM
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Actually colnago...not cool. Merlin is one of the most knowledgeable guys here. Lets not go there.
To put a finer point on it, I think the real dilemma for you colnago is with your weight and strength, is identifying which crank is the strongest. I haven't seen any data to say which crank is.
To echo Merlin's point, design robustness is by intent the ratio of strength to material property variation. No two cranks have the material...material coming into the plant varies day to day within a given tolerance. So if the design isn't robust enough to compensate for normal material variation then failures will ensue when subjected to rider of your weight and strength repeatedly over time. Strength of course has a cost in terms of weight and weight is the enemy on a racing bike. So the term design defect is really misleading. Your crank would not have failed with me riding the bike. Hope this makes sense.
To put a finer point on it, I think the real dilemma for you colnago is with your weight and strength, is identifying which crank is the strongest. I haven't seen any data to say which crank is.
To echo Merlin's point, design robustness is by intent the ratio of strength to material property variation. No two cranks have the material...material coming into the plant varies day to day within a given tolerance. So if the design isn't robust enough to compensate for normal material variation then failures will ensue when subjected to rider of your weight and strength repeatedly over time. Strength of course has a cost in terms of weight and weight is the enemy on a racing bike. So the term design defect is really misleading. Your crank would not have failed with me riding the bike. Hope this makes sense.
Last edited by Campag4life; 03-23-15 at 07:33 AM.
03-23-15, 08:09 AM
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You weigh 230lbs. You have a self proclaimed history of breaking just about every piece of a bicycle.
Yet you claim that the design of the Dura Ace spindle is defective because your's broke, and you can google some examples of others breaking.
It's likely as has already been said in this thread that yours broke due a manufacturing defect, with the help of your size.
The reason for the "Whoosh" is you completely missed my point, that designs have tradeoffs, and if you want very light components, there is going to be a tradeoff in durability.
Shimano could have spec'd the spindle in your crank to be 5 times as strong as it is, giving it greater margin for error from manufacturing imperfections.
But it would be heavier, and people including yourself, wouldn't buy them.
The tradeoff in making lighter parts is that they occassionally are going to fail, particularly when used by people at the end of the bell curve.
Yet you claim that the design of the Dura Ace spindle is defective because your's broke, and you can google some examples of others breaking.
It's likely as has already been said in this thread that yours broke due a manufacturing defect, with the help of your size.
The reason for the "Whoosh" is you completely missed my point, that designs have tradeoffs, and if you want very light components, there is going to be a tradeoff in durability.
Shimano could have spec'd the spindle in your crank to be 5 times as strong as it is, giving it greater margin for error from manufacturing imperfections.
But it would be heavier, and people including yourself, wouldn't buy them.
The tradeoff in making lighter parts is that they occassionally are going to fail, particularly when used by people at the end of the bell curve.
03-23-15, 08:19 AM
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Actually colnago...not cool. Merlin is one of the most knowledgeable guys here. Lets not go there.
To put a finer point on it, I think the real dilemma for you colnago is with your weight and strength, is identifying which crank is the strongest. I haven't seen any data to say which crank is.
To echo Merlin's point, design robustness is by intent the ratio of strength to material property variation. No two cranks have the material...material coming into the plant varies day to day within a given tolerance. So if the design isn't robust enough to compensate for normal material variation then failures will ensue when subjected to rider of your weight and strength repeatedly over time. Strength of course has a cost in terms of weight and weight is the enemy on a racing bike. So the term design defect is really misleading. Your crank would not have failed with me riding the bike. Hope this makes sense.
To put a finer point on it, I think the real dilemma for you colnago is with your weight and strength, is identifying which crank is the strongest. I haven't seen any data to say which crank is.
To echo Merlin's point, design robustness is by intent the ratio of strength to material property variation. No two cranks have the material...material coming into the plant varies day to day within a given tolerance. So if the design isn't robust enough to compensate for normal material variation then failures will ensue when subjected to rider of your weight and strength repeatedly over time. Strength of course has a cost in terms of weight and weight is the enemy on a racing bike. So the term design defect is really misleading. Your crank would not have failed with me riding the bike. Hope this makes sense.
03-23-15, 08:52 AM
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I posted two. If you want to bother, there are many more. It also looks like Shimano changed the design slightly on the spindle. I have been riding long enough on the track and road to know that my demographic is not the group road equipment is designed for. I have steel bars on my track bike for a reason.
03-24-15, 06:37 AM
#43
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This got me thinking about the stress risers, and how much more sensitive the "new and improved hollow" axle cranks are to flaws. A small imperfection on an old square taper 17mm diameter I'm betting is less of a concern than the same flaw on the outside of a newer, hollow crank. Time to pull out my copy of "Peterson's Stress Concentration Factors". If so, it's just adding to my opinion that newer cranks, external BB, BB30, etc. really don't add anything for the average rider.
03-24-15, 07:08 AM
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Looking at the picture in post #8 , I would have expected those rims to have rim/spoke failure way before snapping a crank spindle. Certain part of the year we train several times up, with heavy braking coming back down, on a 1/2 mile 28% incline. I don't get much beyond 3,000 miles on those wheels and they have to be rebuilt, by the third time the rims are done.
Appreciate it if you can post a close up picture of the actual fracture, that would be focusing perpendicular to the actual spindle direction towards the fracture.
Edit: never mind, I looked at the other links you posted, I can see exactly what is happening there and why it fails.
Appreciate it if you can post a close up picture of the actual fracture, that would be focusing perpendicular to the actual spindle direction towards the fracture.
Edit: never mind, I looked at the other links you posted, I can see exactly what is happening there and why it fails.
Last edited by ColnagoC40; 03-24-15 at 07:13 AM.
03-24-15, 07:31 AM
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This got me thinking about the stress risers, and how much more sensitive the "new and improved hollow" axle cranks are to flaws. A small imperfection on an old square taper 17mm diameter I'm betting is less of a concern than the same flaw on the outside of a newer, hollow crank. Time to pull out my copy of "Peterson's Stress Concentration Factors". If so, it's just adding to my opinion that newer cranks, external BB, BB30, etc. really don't add anything for the average rider.
On the subject of stress risers or propensity of new versus old cranks, this is pure speculation and unproven. I don't see any more failures of the new versus older stuff. The newer stuff sure is stiffer for stronger riders. Colango is an outlier. He breaks frames, wheels and cranks. A beast.
03-24-15, 07:38 AM
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I am beginning to think bad design. https://fcdn.mtbr.com/attachments/fat...lure-broke.jpgAustralian Cycling Forums - Broken Dura Ace 7900 Crankset
I'm glad you weren't injured when it broke. I know someone who broke one of the first DA hollowtech cranks during a race and he didn't fare as well.
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03-24-15, 02:09 PM
#47
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I don't agree. I much prefer a modern DA or Campy UT to any square taper. I have worked on 100 square taper BB's and never liked the design.
On the subject of stress risers or propensity of new versus old cranks, this is pure speculation and unproven. I don't see any more failures of the new versus older stuff. The newer stuff sure is stiffer for stronger riders. Colango is an outlier. He breaks frames, wheels and cranks. A beast.
On the subject of stress risers or propensity of new versus old cranks, this is pure speculation and unproven. I don't see any more failures of the new versus older stuff. The newer stuff sure is stiffer for stronger riders. Colango is an outlier. He breaks frames, wheels and cranks. A beast.
03-24-15, 04:16 PM
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I've had quite the different experience. Since 1984, have owned 8 bikes with square taper (all OEM) without a problem. The one external BB crank failed at the interface between the spider and spindle. Therefore, I'm still dubious as to any advantage over square taper. As for stiffness being any advantage, that's been beaten to death around here
Last edited by Campag4life; 03-24-15 at 04:22 PM.
03-24-15, 09:27 PM
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Trek uses a BB90 bottom bracket. I have had nothing but issues with it. I have to replace the bearings every couple of months. The last set were installed on November 27th. They were inspected in mid February. Due to the break, the mechanic checked them again and said they were toast. That is how it's been going since I have owned the bike.