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#1
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Clicking square taper cranks - fixable?
I have a friend who brought his bike to me to look at (because he's too
cheap for the LBS and most days I can work out which end of the wrench to hold) His square taper cranks are clicking, and he says he has ridden about 50 miles since he first heard it (which I'd guess means he's done about 20). Now, the bolt holding the cranks onto the BB wasn't very tight, so I tightened it with an 8mm alan key in a bit of pipe. The noise has gone away, but I had to tighten it a lot so it seems the cranks have been pushed up the taper. The chainline may have been reduced a little, but probably in itself this isn't such a bad thing since it was a tad outboard before. In this situation, is it a case of tighten it up really good once and it'll be fixed forever, or is it just going to need retightening over and over and eventually ride up the taper far enough to crack the cranks? I'm not a pro mechanic, but I don't want my friend to be injured. At the same time, I don't want to tell him to spend money he doesn't have to. |
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#2
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Clicking square taper cranks - fixable?
Quoth Jim Higson:
...square taper cranks are clicking, and he says he has ridden about 50 miles since he first heard it (which I'd guess means he's done about 20). Now, the bolt holding the cranks onto the BB wasn't very tight, so I tightened it with an 8mm alan key in a bit of pipe. The noise has gone away, but I had to tighten it a lot so it seems the cranks have been pushed up the taper. The chainline may have been reduced a little, but probably in itself this isn't such a bad thing since it was a tad outboard before. In this situation, is it a case of tighten it up really good once and it'll be fixed forever, or is it just going to need retightening over and over and eventually ride up the taper far enough to crack the cranks? Depends how much it was ridden while loose. I would remove the crank, grease the spindle, grease the bolt threads, grease the underside of the bolt head, then tighten the bejasus out of it. If it isn't wrecked, this will do the trick. I'm not a pro mechanic, but I don't want my friend to be injured. At the same time, I don't want to tell him to spend money he doesn't have to. There's not a major risk of injury here. If it doesn't work, the symptom will be that the crank will loosen up again, nothing is likely to snap off. Sheldon "Unnnnnnngggh!" Brown +---------------------------------------------------------------+ | There are 10 kinds of people in this world: | | Those who understand the binary system, and those who don't | +---------------------------------------------------------------+ Harris Cyclery, West Newton, Massachusetts Phone 617-244-9772 FAX 617-244-1041 http://harriscyclery.com Hard-to-find parts shipped Worldwide http://captainbike.com http://sheldonbrown.com |
#3
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Clicking square taper cranks - fixable?
Sheldon Brown advised:
...square taper cranks are clicking, and he says he has ridden about 50 miles since he first heard it (which I'd guess means he's done about 20). Now, the bolt holding the cranks onto the BB wasn't very tight, so I tightened it with an 8mm alan key in a bit of pipe. The noise has gone away, but I had to tighten it a lot so it seems the cranks have been pushed up the taper. The chainline may have been reduced a little, but probably in itself this isn't such a bad thing since it was a tad outboard before. In this situation, is it a case of tighten it up really good once and it'll be fixed forever, or is it just going to need retightening over and over and eventually ride up the taper far enough to crack the cranks? Depends how much it was ridden while loose. I would remove the crank, grease the spindle, grease the bolt threads, grease the underside of the bolt head, then tighten the bejasus out of it. If it isn't wrecked, this will do the trick. Ok, when I need a really big lever I use a bolt cutter with a good strong hollow 90cm handle to put the key inside. Should be able to get it very tight indeed. Normally I use it to undo stuck bolts. The look on people's faces when I get the large bolt cutters out to get something off their bike, by the way, is priceless :-) Square taper Campag BBs and chainsets are going for silly money here at the moment so if it is a write-off, at least it can be cheaply replaced. One place has Mirage BBs for £2.50. I'm not a pro mechanic, but I don't want my friend to be injured. At the same time, I don't want to tell him to spend money he doesn't have to. There's not a major risk of injury here. If it doesn't work, the symptom will be that the crank will loosen up again, nothing is likely to snap off. Heh, in that case this actually seems like quite a good way of getting a slightly shorter effective BB spindle length when finetuning the chainline. Thanks. -- Jim |
#4
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Clicking square taper cranks - fixable?
On Feb 7, 1:35 pm, Jim Higson wrote:
Sheldon Brown advised: ...square taper cranks are clicking, and he says he has ridden about 50 miles since he first heard it (which I'd guess means he's done about 20). Now, the bolt holding the cranks onto the BB wasn't very tight, so I tightened it with an 8mm alan key in a bit of pipe. The noise has gone away, but I had to tighten it a lot so it seems the cranks have been pushed up the taper. The chainline may have been reduced a little, but probably in itself this isn't such a bad thing since it was a tad outboard before. In this situation, is it a case of tighten it up really good once and it'll be fixed forever, or is it just going to need retightening over and over and eventually ride up the taper far enough to crack the cranks? Depends how much it was ridden while loose. I would remove the crank, grease the spindle, grease the bolt threads, grease the underside of the bolt head, then tighten the bejasus out of it. If it isn't wrecked, this will do the trick. Ok, when I need a really big lever I use a bolt cutter with a good strong hollow 90cm handle to put the key inside. Should be able to get it very tight indeed. Normally I use it to undo stuck bolts. Careful.....you do not want to get carried away and damage the bolt, especially in a way that would make it hard to remove (I once snapped the head off a crank bolt in a moment of ham fisted madness). The look on people's faces when I get the large bolt cutters out to get something off their bike, by the way, is priceless :-) Square taper Campag BBs and chainsets are going for silly money here at the moment so if it is a write-off, at least it can be cheaply replaced. One place has Mirage BBs for £2.50. I'm not a pro mechanic, but I don't want my friend to be injured. At the same time, I don't want to tell him to spend money he doesn't have to. There's not a major risk of injury here. If it doesn't work, the symptom will be that the crank will loosen up again, nothing is likely to snap off. Heh, in that case this actually seems like quite a good way of getting a slightly shorter effective BB spindle length when finetuning the chainline. Thanks. -- Jim- Hide quoted text - - Show quoted text - |
#5
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Clicking square taper cranks - fixable?
Ozark Bicycle wrote:
In this situation, is it a case of tighten it up really good once and it'll be fixed forever, or is it just going to need retightening over and over and eventually ride up the taper far enough to crack the cranks? Depends how much it was ridden while loose. I would remove the crank, grease the spindle, grease the bolt threads, grease the underside of the bolt head, then tighten the bejasus out of it. If it isn't wrecked, this will do the trick. Ok, when I need a really big lever I use a bolt cutter with a good strong hollow 90cm handle to put the key inside. Should be able to get it very tight indeed. Normally I use it to undo stuck bolts. Careful.....you do not want to get carried away and damage the bolt, especially in a way that would make it hard to remove (I once snapped the head off a crank bolt in a moment of ham fisted madness). Well, I wasn't going to put my full weight on the end of the 90cm lever, just enough torque for all residual bejasus to be removed. |
#6
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Clicking square taper cranks - fixable?
On Feb 7, 2:01 pm, Jim Higson wrote:
Ozark Bicycle wrote: In this situation, is it a case of tighten it up really good once and it'll be fixed forever, or is it just going to need retightening over and over and eventually ride up the taper far enough to crack the cranks? Depends how much it was ridden while loose. I would remove the crank, grease the spindle, grease the bolt threads, grease the underside of the bolt head, then tighten the bejasus out of it. If it isn't wrecked, this will do the trick. Ok, when I need a really big lever I use a bolt cutter with a good strong hollow 90cm handle to put the key inside. Should be able to get it very tight indeed. Normally I use it to undo stuck bolts. Careful.....you do not want to get carried away and damage the bolt, especially in a way that would make it hard to remove (I once snapped the head off a crank bolt in a moment of ham fisted madness). Well, I wasn't going to put my full weight on the end of the 90cm lever, just enough torque for all residual bejasus to be removed. My snapped-the-head-off misadventure was done using a regular 3/8" socket drive, and I was just trying to get it 'really tight', not any more than that. |
#7
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Clicking square taper cranks - fixable?
"Ozark Bicycle" wrote in message ups.com... On Feb 7, 2:01 pm, Jim Higson wrote: Ozark Bicycle wrote: In this situation, is it a case of tighten it up really good once and it'll be fixed forever, or is it just going to need retightening over and over and eventually ride up the taper far enough to crack the cranks? Depends how much it was ridden while loose. I would remove the crank, grease the spindle, grease the bolt threads, grease the underside of the bolt head, then tighten the bejasus out of it. If it isn't wrecked, this will do the trick. Ok, when I need a really big lever I use a bolt cutter with a good strong hollow 90cm handle to put the key inside. Should be able to get it very tight indeed. Normally I use it to undo stuck bolts. Careful.....you do not want to get carried away and damage the bolt, especially in a way that would make it hard to remove (I once snapped the head off a crank bolt in a moment of ham fisted madness). Well, I wasn't going to put my full weight on the end of the 90cm lever, just enough torque for all residual bejasus to be removed. My snapped-the-head-off misadventure was done using a regular 3/8" socket drive, and I was just trying to get it 'really tight', not any more than that. You can overtighten the crank bolts which can cause the square taper to stretch a little thus reducing the contact area of the small end of the taper. This happens frequently on machinery that runs on hardened steel taper drives. Chas. |
#8
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Clicking square taper cranks - fixable?
In this situation, is it a case of tighten it up really good
once and it'll be fixed forever, or is it just going to need retightening over and over and eventually ride up the taper far enough to crack the cranks? Depends how much it was ridden while loose. I would remove the crank, grease the spindle, grease the bolt threads, grease the underside of the bolt head, then tighten the bejasus out of it. If it isn't wrecked, this will do the trick. Ok, when I need a really big lever I use a bolt cutter with a good strong hollow 90cm handle to put the key inside. Should be able to get it very tight indeed. Normally I use it to undo stuck bolts. Ozark Bicycle wrote: Careful.....you do not want to get carried away and damage the bolt, especially in a way that would make it hard to remove (I once snapped the head off a crank bolt in a moment of ham fisted madness). Jim Higson wrote: Well, I wasn't going to put my full weight on the end of the 90cm lever, just enough torque for all residual bejasus to be removed. "Ozark Bicycle" wrote: My snapped-the-head-off misadventure was done using a regular 3/8" socket drive, and I was just trying to get it 'really tight', not any more than that. * * Chas wrote: You can overtighten the crank bolts which can cause the square taper to stretch a little thus reducing the contact area of the small end of the taper. This happens frequently on machinery that runs on hardened steel taper drives. Yes with repeated torque but not at one time. I used to have a big-bicep employee who routinely snapped off crank bolts before we got her to use a torque wrench. The bolt head breaks before you damage the crank. -- Andrew Muzi www.yellowjersey.org Open every day since 1 April, 1971 |
#9
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Clicking square taper cranks - fixable?
"A Muzi" wrote in message ... In this situation, is it a case of tighten it up really good once and it'll be fixed forever, or is it just going to need retightening over and over and eventually ride up the taper far enough to crack the cranks? Depends how much it was ridden while loose. I would remove the crank, grease the spindle, grease the bolt threads, grease the underside of the bolt head, then tighten the bejasus out of it. If it isn't wrecked, this will do the trick. Ok, when I need a really big lever I use a bolt cutter with a good strong hollow 90cm handle to put the key inside. Should be able to get it very tight indeed. Normally I use it to undo stuck bolts. Ozark Bicycle wrote: Careful.....you do not want to get carried away and damage the bolt, especially in a way that would make it hard to remove (I once snapped the head off a crank bolt in a moment of ham fisted madness). Jim Higson wrote: Well, I wasn't going to put my full weight on the end of the 90cm lever, just enough torque for all residual bejasus to be removed. "Ozark Bicycle" wrote: My snapped-the-head-off misadventure was done using a regular 3/8" socket drive, and I was just trying to get it 'really tight', not any more than that. * * Chas wrote: You can overtighten the crank bolts which can cause the square taper to stretch a little thus reducing the contact area of the small end of the taper. This happens frequently on machinery that runs on hardened steel taper drives. Yes with repeated torque but not at one time. I used to have a big-bicep employee who routinely snapped off crank bolts before we got her to use a torque wrench. The bolt head breaks before you damage the crank. -- Andrew Muzi www.yellowjersey.org I've only broken 1crank bolt from over tightening in 35+ years. I have a torque wrench, I should use it. What torque specs do you use for M8 x 1.0 crank bolts? Chas. |
#10
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Clicking square taper cranks - fixable?
On Feb 8, 8:28 am, "* * Chas" wrote:
I've only broken 1crank bolt from over tightening in 35+ years. I have a torque wrench, I should use it. What torque specs do you use for M8 x 1.0 crank bolts? Though the question was not addressed to me, never mind my far poorer experience than you guys have, I feel like jumping in and giving my own answer. Around here I have never seen any (expert) mechanic use a dynanometric wrench while tightening such bolts. My way of approaching such a problem is quite pragmatic, in fact. Given that God Tullio has made a wrench that long, rather short in fact, for my arms to use, and that all Goddesses recommend everything be clean and lubricated, I do clean, lube and turn by feel. No failure, so far. Sergio Pisa |
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