repeatedly installing/removing square taper cranks...
#1
snupontgeam
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repeatedly installing/removing square taper cranks...
How many times can this be done? Does the crank begin to deform more and more eventually finishing the crank?
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A normal amount of removal and installation shouldn't be an issue. I've got some XTR cranks that must be about 12-13 years old now, and still haven't given up the ghost (great, now I've jinxed myself ).
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Why is this going to be an issue? You removing them and reinstalling them before you sleep each time? The more times you take it on and off the greater chance for damage, especially if you aren't using a torque wrench.
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snupontgeam
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I'll only be removing them a normal amount... for bb upkeep. Mainly I was just wondering when it would this would become a problem. I'd read that it can be a problem, but I was wondering if it takes.... 6-10 times? 10-20 times? you know like what ball park.
And yes I do use a torque wrench.
And yes I do use a torque wrench.
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This is one place a torque wrench is good to have so that you don't broach the crank.I've torqued my SR crank/Shimano BB to 40 ft-lbs for the last 30 years,no problems.I've put in or serviced it about 25/30 times.
I torque them down,leave the cap off,ride around the block a few times,check again,put caps on.Then I check every few days a couple times,just to make sure.Cheaper than a new arm.
I torque them down,leave the cap off,ride around the block a few times,check again,put caps on.Then I check every few days a couple times,just to make sure.Cheaper than a new arm.
Last edited by Booger1; 11-10-08 at 12:51 AM.
#8
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That's kinda overtightening it at 40-lbs. But you're more likely to cause damage by under-tightening them. All it takes is for them to come loose just once and you've buggered the square-taper hole and it'll never, ever fit right again.
I've found it's a lot more secure to replace the flat washer with a star-lockwasher if you're going to be removing the cranks a lot. Reduces the chance that a well-used bolt with worn threads may come loose. Usually a good practice to use new bolts every 10th time you've re-installed the cranks.
I've found it's a lot more secure to replace the flat washer with a star-lockwasher if you're going to be removing the cranks a lot. Reduces the chance that a well-used bolt with worn threads may come loose. Usually a good practice to use new bolts every 10th time you've re-installed the cranks.
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All it takes is for them to come loose just once and you've buggered the square-taper hole and it'll never, ever fit right again.
I've found it's a lot more secure to replace the flat washer with a star-lockwasher if you're going to be removing the cranks a lot. Reduces the chance that a well-used bolt with worn threads may come loose. Usually a good practice to use new bolts every 10th time you've re-installed the cranks.
The better solution for the OP is to stick a cartridge bb and forget about having to regularly overhauling the bb and it's subsequent problems. Time to get with the 21st century.
#11
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I have the same crank arms on my 33 year old bike, and they haven't worn out yet (oops, now they will wear out next week for sure....)
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You will effect the chain line each time you remount the cranks by moving it in a small amount. Amount depends on the crank and bottom bracket axle, as well as the torque. You will also wear the threads on the bolts and inside the axle. I suggest using DuPont Krytox on the threads and under the washers.
We travel with an S & S Coupled tandem. We got 20 trips in before the XT cranks became so worn that we could no longer use them. We don't apply lube on the crank axle square tapers but we do use a torque wrench each time to tighten the bolts.
We travel with an S & S Coupled tandem. We got 20 trips in before the XT cranks became so worn that we could no longer use them. We don't apply lube on the crank axle square tapers but we do use a torque wrench each time to tighten the bolts.
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I also have an S&S coupled bike so the 105 square taper crank has been off and reinstalled a dozen or more times. I've never had to touch the limit screws or indexing adjustment.
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Well, your method seems to be a good argument for lightly greasing the tapers.
We did need to touch up limit screws and JumpStop adjustments every other trip. We didn't need to readjust the rear derailer.
We did need to touch up limit screws and JumpStop adjustments every other trip. We didn't need to readjust the rear derailer.
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There isn't a lot of BB upkeep to do with a Phil Wood. It might be 5 years before you have to do anything other than an occaisional retorque. bk
Last edited by bkaapcke; 11-10-08 at 04:37 PM.
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If you only got 20 cycles of an XT crank, then you did something wrong. Seriously.
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I've been a machinist for almost 40 years,and I can tell you for a FACT that 40# will not broach forged aluminum,even crappy forgings.It takes around 200# of force to push a broaching tool thru an aluminum forging to cut a 3/8 keyway,and the broaching tool has carbide teeth on it.ID broaching tools cut on a taper,just like BB's.Imagine how much force it would take to push a BB spindle thru a forging with NO cutting teeth on it.
35-40 Ft/lbs is NOT going to broach a GOOD FORGED aluminum arm,EVER.Were talking 10#-15# over the recommended torque that gets used these days,spread out over the surface area of the spindle(1 1/2-2 sq-in or so),that's nothing.
I'm sure most of the men on this site can push a 100# with their hands,anybody think they can push hard enough to broach the crank arm out?....What if I get a 400# guy to sit on the crank arm,think that will do it? My guess is that most the problems we hear about are from cranks that have come loose,egged out the hole,then the fun begins.
In 1978 when I bought the bike,the shop told me that's what the torque was,been using it ever since.It may be too tight for the "professionals",but my cranks never come loose and the chainline is still fine after 30 years,so I'm sticking with what works.If it last another 30 years ,I'll be dead,someone else will have to worry about it.
35-40 Ft/lbs is NOT going to broach a GOOD FORGED aluminum arm,EVER.Were talking 10#-15# over the recommended torque that gets used these days,spread out over the surface area of the spindle(1 1/2-2 sq-in or so),that's nothing.
I'm sure most of the men on this site can push a 100# with their hands,anybody think they can push hard enough to broach the crank arm out?....What if I get a 400# guy to sit on the crank arm,think that will do it? My guess is that most the problems we hear about are from cranks that have come loose,egged out the hole,then the fun begins.
In 1978 when I bought the bike,the shop told me that's what the torque was,been using it ever since.It may be too tight for the "professionals",but my cranks never come loose and the chainline is still fine after 30 years,so I'm sticking with what works.If it last another 30 years ,I'll be dead,someone else will have to worry about it.
Last edited by Booger1; 11-10-08 at 01:47 PM.
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Also, older cranks may have nutted spindles, rather than bolted, and they generally appreciate more torque.
In the bigger picture, if someone's worried about this issue, there's always Hollowtech II or Octalink
In the bigger picture, if someone's worried about this issue, there's always Hollowtech II or Octalink
Last edited by mechBgon; 11-10-08 at 12:45 PM.
#19
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if you use a torque wrench every time you install them, indefinitely
I use 27 ft lbs each time. 25 is the standard and 30 won't kill ya either
I use 27 ft lbs each time. 25 is the standard and 30 won't kill ya either
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20 trips = 40 cycles as we re-stalled the cranks to ride around home too.
I am stating what I observed and experienced.
I can't give exact quantifiable data as to how much the chain line changed, but I know that I readjusted the front derailer stops and the JumpStop 10 times during the life of the crank. The cranks had around 52k miles and were replaced a couple years ago along with the bottom brackets.
We are now using Octalink BBs and cranks, so I don't see any movement in the chain line now.
I am stating what I observed and experienced.
I can't give exact quantifiable data as to how much the chain line changed, but I know that I readjusted the front derailer stops and the JumpStop 10 times during the life of the crank. The cranks had around 52k miles and were replaced a couple years ago along with the bottom brackets.
We are now using Octalink BBs and cranks, so I don't see any movement in the chain line now.
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I've been a machinist for almost 40 years,and I can tell you for a FACT that 40# will not broach forged aluminum,even crappy forgings.It takes around 200# of force to push a broaching tool thru an aluminum forging to cut a 3/8 keyway,and the broaching tool has carbide teeth on it.ID broaching tools cut on a taper,just like BB's.Imagine how much force it would take to push a BB spindle thru a forging with NO cutting teeth on it.
35-40 Ft/lbs is NOT going to broach a GOOD FORGED aluminum arm,EVER.Were talking 10#-15# over the recommended torque that gets used these days,spread out over the surface area of the spindle(1 1/2-2 sq-in or so),that's nothing.
I'm sure most of the men on this site can push a 100# with their hands,anybody think they can push hard enough to broach the crank arm out?....What if I get a 400# guy to sit on the crank arm,think that will do it? My guess is that most the problems we hear about are from cranks that have come loose,egged out the hole,then the fun begins.
In 1978 when I bought the bike,the shop told me that's what the torque was,been using it ever since.It may be too tight for the "professionals",but my cranks never come loose and the chainline is still fine after 30 years,so I'm sticking with what works.If it last another 30 years ,I'll be dead,someone else will have to worry about it.
35-40 Ft/lbs is NOT going to broach a GOOD FORGED aluminum arm,EVER.Were talking 10#-15# over the recommended torque that gets used these days,spread out over the surface area of the spindle(1 1/2-2 sq-in or so),that's nothing.
I'm sure most of the men on this site can push a 100# with their hands,anybody think they can push hard enough to broach the crank arm out?....What if I get a 400# guy to sit on the crank arm,think that will do it? My guess is that most the problems we hear about are from cranks that have come loose,egged out the hole,then the fun begins.
In 1978 when I bought the bike,the shop told me that's what the torque was,been using it ever since.It may be too tight for the "professionals",but my cranks never come loose and the chainline is still fine after 30 years,so I'm sticking with what works.If it last another 30 years ,I'll be dead,someone else will have to worry about it.
I want to know the appropriate torque because I do not want to break the bolt (too much torque) and I do not want the crank coming loose (too little torque).
#22
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About 22-25# is about what the manufacturers recommend. I usually go a little higher to 30# and haven't had any problems.
#23
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For the record, you can have a crank come loose on you and not ruin it, you just have to catch it early. There is a definite feel when the crank first starts to come loose, and as long as you catch is there, no damage will be done. Argue all you like, but I've felt my crank loosen (my fault, it was the one time i didn't use a torque wrench), but I caught it, pedaled home with 1 foot. When I checked it, the tapers were still fine.
I wouldn't recommend it, but just letting you know one loosen isn't death.
I wouldn't recommend it, but just letting you know one loosen isn't death.
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I'm sure some of the problems people have,is not their fault.Like Daveornee above,where he had his arm screw up after 20 times on and off.He probably did everything by the book.
If the taper angles don't match well when new,everytime you take the arm off and put it back on,the arm will recede on the spindle a tiny bit until the surface area is big enough to hold the forces involved.So then it ends up being a race between the arm receding and enough surface area on the mating surfaces on the tapers.Depending on who wins the race,determines if the bolt/nut bottoms on the end of the spindle or not.
If the taper angles don't match well when new,everytime you take the arm off and put it back on,the arm will recede on the spindle a tiny bit until the surface area is big enough to hold the forces involved.So then it ends up being a race between the arm receding and enough surface area on the mating surfaces on the tapers.Depending on who wins the race,determines if the bolt/nut bottoms on the end of the spindle or not.
Last edited by Booger1; 11-10-08 at 10:00 PM.
#25
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Should one keep the same orientation of the crank arms on the spindles? In other words, should the arms go on in the same position as they came from? Does it even matter? I've always put mine on in the same location that they came from and never had any problems, in the 25 years of doing this, on my various bikes.