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Old 11-09-08, 08:14 PM   #1
patrick.decker@
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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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Old 11-09-08, 08:30 PM   #2
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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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Old 11-09-08, 08:42 PM   #3
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How many times can this be done? Does the crank begin to deform more and more eventually finishing the crank?
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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Old 11-09-08, 08:52 PM   #4
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it only takes one bad installation to deform the crank - I know, I've done it.

but, as long as you do it right everytime, no problem.
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Old 11-09-08, 08:53 PM   #5
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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.
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Old 11-10-08, 12:12 AM   #6
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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.
What is the proper torque value for a Campagnolo crank onto a Phil Wood bottom Bracket?
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Old 11-10-08, 12:26 AM   #7
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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.

Last edited by Booger1; 11-10-08 at 12:51 AM.
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Old 11-10-08, 12:56 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.
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Old 11-10-08, 07:08 AM   #9
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What is the proper torque value for a Campagnolo crank onto a Phil Wood bottom Bracket?
Going to have to ask you which campy crank you have.
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Old 11-10-08, 07:16 AM   #10
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That's kinda overtightening it at 40-lbs. But you're more likely to cause damage by under-tightening them.
No, by tightening them that much he's more likely to damage them to overtightening. Which he is doing by an extreme margin, already. 35Nm for square taper cranks with 8mm hex bolts is generally enough. And that is quite tight already

Quote:
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.
And all it takes is for one slide too far on the spindle if you overtighten.

Quote:

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.
Bolts come loose because of inadequate torque. If you're really that worried about it coming loose treat the threads with loctite. Which really ins't necessary. Using a star washer only serves to damage the crank.

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.
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Old 11-10-08, 07:34 AM   #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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Old 11-10-08, 08:58 AM   #12
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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.
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Old 11-10-08, 09:47 AM   #13
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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.
I haven't found this to be the case on a wide variety of cranks square taper including SR, Sun Tour, Shimano and Campy. I remove them for bb maintainence and reinstall them to the proper torque ( I do lightly grease the spindle taper - a BIG argument in itself) and the chainline does not move at all.

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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Old 11-10-08, 10:19 AM   #14
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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.
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Old 11-10-08, 10:29 AM   #15
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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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Old 11-10-08, 10:43 AM   #16
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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.
If you only got 20 cycles of an XT crank, then you did something wrong. Seriously.
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Old 11-10-08, 12:36 PM   #17
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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.

Last edited by Booger1; 11-10-08 at 01:47 PM.
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Old 11-10-08, 12:42 PM   #18
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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

Last edited by mechBgon; 11-10-08 at 12:45 PM.
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Old 11-10-08, 12:46 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
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Old 11-10-08, 12:49 PM   #20
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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.
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Old 11-10-08, 02:27 PM   #21
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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.
The "ring" of truth. You know it when you hear 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).
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Old 11-10-08, 04:14 PM   #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.
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Old 11-10-08, 04:39 PM   #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.
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Old 11-10-08, 09:45 PM   #24
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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.

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Old 11-11-08, 08:25 AM   #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.
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