Why do cranks fall off so often?
02-18-09, 04:08 PM
#1
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Why do cranks fall off so often?
Why do cranks fall off so often? You think somebody could invent a better way to keep them on.
(Bikeforums will only allow me to post 10 pictures)
(Bikeforums will only allow me to post 10 pictures)
02-18-09, 04:10 PM
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PS: It's funniest when the crank is still stuck to their foot.
It happened to a guy I was racing, and the neutral support guys put his crank back on and got the guy back into the race. Then the support guys fell over laughing.
It happened to a guy I was racing, and the neutral support guys put his crank back on and got the guy back into the race. Then the support guys fell over laughing.
02-18-09, 04:18 PM
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I think it's a conspiracy attempting to force people into one leg drills. I for one think it's a great idea. If only it was not always the left side!
02-18-09, 04:22 PM
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I looked like that discovery guy one time in 2007. Madden voyage on my new 10 speed Dura Ace group. Turns out I had not installed it properly. You would think that a pro team mechanic would have no problem installing a crank like that but, I'm just saying.
02-18-09, 04:23 PM
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02-18-09, 04:36 PM
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The left crank has to transmit torque through the spindle. The right one doesn't. The inferface between the crank and spindle is therefore more critical on the left side. The torque along with any wobbling forces will work the bolt loose over time if it's not securely fastened to the correct torque the very first time the crank is installed.
IF the crank comes loose just once, it'll end up wobbling and buggering itself on the hard steel spindle and the square taper in the crank is bullocks for good. Just loosening once is all it takes to destroy the crank. Trying to put it back on again and again is a futile effort, even if you torque it down properly the 2nd time. It'll never fit as tight and won't stay put.
IF the crank comes loose just once, it'll end up wobbling and buggering itself on the hard steel spindle and the square taper in the crank is bullocks for good. Just loosening once is all it takes to destroy the crank. Trying to put it back on again and again is a futile effort, even if you torque it down properly the 2nd time. It'll never fit as tight and won't stay put.
02-18-09, 04:39 PM
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don't look here then: https://pardo.net/pardo/bike/pic/fail/000.html
02-18-09, 04:43 PM
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The left crank has to transmit torque through the spindle. The right one doesn't. The inferface between the crank and spindle is therefore more critical on the left side. The torque along with any wobbling forces will work the bolt loose over time if it's not securely fastened to the correct torque the very first time the crank is installed.
IF the crank comes loose just once, it'll end up wobbling and buggering itself on the hard steel spindle and the square taper in the crank is bullocks for good. Just loosening once is all it takes to destroy the crank. Trying to put it back on again and again is a futile effort, even if you torque it down properly the 2nd time. It'll never fit as tight and won't stay put.
IF the crank comes loose just once, it'll end up wobbling and buggering itself on the hard steel spindle and the square taper in the crank is bullocks for good. Just loosening once is all it takes to destroy the crank. Trying to put it back on again and again is a futile effort, even if you torque it down properly the 2nd time. It'll never fit as tight and won't stay put.
But with any other system besides square tapper that shouldn't be much of an issue.
02-18-09, 04:43 PM
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don't look here then: https://pardo.net/pardo/bike/pic/fail/000.html
I had a Campy Record crank fall off once; never had a Shimano fall off. Not that I'm insinuating that Shimanos are better than Campys, because the Campys were hot. But the Campys are just as prone to failure as the Shimanos are.
Also had a Truvativ fall off. Gah, that was a bad crankset.
EDIT: As hinted at above, I'm talking about square-taper cranks. Newer styles may be more reliable.
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Last edited by iamtim; 02-18-09 at 04:46 PM. Reason: Cuz I could.
02-18-09, 04:48 PM
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only time I had a crank arm come loose and fall off was when I was about 15 and bought a krappy mountain bike at kmart or some place similar.
Or that time I got t-boned by a car and my BB snapped removing the left arm..
Or that time I got t-boned by a car and my BB snapped removing the left arm..
02-18-09, 05:11 PM
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I want to see a pic with someone's foot still attached to the right crank... chainrings and all!
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02-18-09, 05:32 PM
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+1.
I had a Campy Record crank fall off once; never had a Shimano fall off. Not that I'm insinuating that Shimanos are better than Campys, because the Campys were hot. But the Campys are just as prone to failure as the Shimanos are.
Also had a Truvativ fall off. Gah, that was a bad crankset.
EDIT: As hinted at above, I'm talking about square-taper cranks. Newer styles may be more reliable.
I had a Campy Record crank fall off once; never had a Shimano fall off. Not that I'm insinuating that Shimanos are better than Campys, because the Campys were hot. But the Campys are just as prone to failure as the Shimanos are.
Also had a Truvativ fall off. Gah, that was a bad crankset.
EDIT: As hinted at above, I'm talking about square-taper cranks. Newer styles may be more reliable.
02-18-09, 05:43 PM
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I call shenanigans (which I will happily retract if you can provide proof of said survey.)
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02-18-09, 06:09 PM
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Sounds like a lot of user error out there ! Don't blame the part.
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02-18-09, 06:18 PM
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02-18-09, 06:25 PM
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02-18-09, 06:28 PM
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02-18-09, 06:38 PM
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I have never had a crank arm fall off, but I've had them come loose more than once. With square taper, you get off the bike, kick the arm a couple of times, tighten the bolt by hand. Ride a couple miles and repeat the above procedure. If you get tired of kicking, do the one leg drill thing for a while.