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Old 08-20-07, 07:15 PM   #1
mike
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Grease the BB spindle/axle?

I know this question has been asked a million - no make that a kajillion - times before. I apologize to fellow BF.net junkies who see this stuff et nausium.

Ah.

'n so, here is the question: "Should bottom bracket spindles be greased before putting the crank arms?"

Of course, I know, or think I know that the answer is "no". However, I just had a terrible time removing a stuck crank - had to cut it off (see the other thread).

Now I am wondering... hmm. Should you grease the spindle so it will come off at a future date? OR, will this lead to a cronic loose crank arm?

Any thoughts, oh my beautiful mechanic friends?
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Old 08-20-07, 07:26 PM   #2
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Is it a campy or shimano crank?
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Old 08-20-07, 07:43 PM   #3
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Slined- yes , Square tapered- no
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Old 08-20-07, 09:31 PM   #4
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+1

(though, in truth, I doubt it matters much)
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Old 08-21-07, 02:03 AM   #5
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Is it a campy or shimano crank?
Shimano. (Does that matter?)
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Old 08-21-07, 06:21 AM   #6
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AFAIK, Shimano doesn't say either way for square tapers and yes for Octalink. Campagnolo says absolutely not for square tapers.

However, a mechanical engineer I know who is an expert on clamped interference fit parts says grease on square taper cranks is definitely a good idea. What he also says is to torque the crank to spec once when the arms are installed and then leave them alone. The damage is done by repetatively retorquing the fixing bolts which "chases" the arms up the taper until they are distorted or crack.
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Old 08-21-07, 06:33 AM   #7
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However, a mechanical engineer I know who is an expert on clamped interference fit parts says grease on square taper cranks is definitely a good idea. What he also says is to torque the crank to spec once when the arms are installed and then leave them alone. The damage is done by repetatively retorquing the fixing bolts which "chases" the arms up the taper until they are distorted or crack.
Well, that's a brilliant idea considering everyone has the appropriate torque wrench in their tool box. Did he give a good con for NOT greasing the spindle?
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Old 08-21-07, 06:40 AM   #8
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Well, that's a brilliant idea considering everyone has the appropriate torque wrench in their tool box. Did he give a good con for NOT greasing the spindle?
It's not "brilliant", it's mechanical fact. If you don't torque the bolts to at least close to the specified value, it doesn't matter what else you do. Search this forum for all of the "my crank came loose" threads for evidence.

The con was that the initial fit of dry surfaces is unpredictable due to the unknown coefficient of friction and the degree of interference. A greased interface makes the fit much more predictable.
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Old 08-21-07, 06:44 AM   #9
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FWIW, the last two Shimano bottom brackets I bought (UN-54's), came significantly oiled in the packaging. The oil felt a lot like low viscosity motor oil. I assume it was done at least for corrosion resistance during storage and possibly for installation as well. I left the oil on when I installed the cranks.

I only mention this because I had previously bought two other square taper Shimano bottom brackets and neither of them came oiled, though they were a lower end model.
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Old 08-21-07, 06:51 AM   #10
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It's not "brilliant", it's mechanical fact. If you don't torque the bolts to at least close to the specified value, it doesn't matter what else you do. Search this forum for all of the "my crank came loose" threads for evidence.
Oh please. If you're the guy installing crank bolts without a torque wrench, you KNOW you have to keep rechecking the bolts after a ride or two to make sure they haven't come loose.

You make it sound as if they only way you could ever put cranks on right is to use a torque wrench. And for the record "my cranks came loose" threads should also have an equal if not greater amount of threads that state "my cranks didn't come loose".
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Old 08-21-07, 06:56 AM   #11
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Same here. If you ever get a square taper steel axle and a alu crank "welded" together, you know why. I've never had a problem with cranks working loose doing this either, and only ever had problems removing cranks when they were put on by other people who -and I think I'm pretty sure here -didn't use anything. Anti-seize is the way to go! (never dealt with carbon though).
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Old 08-21-07, 07:12 AM   #12
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Oh please. If you're the guy installing crank bolts without a torque wrench, you KNOW you have to keep rechecking the bolts after a ride or two to make sure they haven't come loose.
Yes you do and what you "know" is incorrect and damaging.

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You make it sound as if they only way you could ever put cranks on right is to use a torque wrench. And for the record "my cranks came loose" threads should also have an equal if not greater amount of threads that state "my cranks didn't come loose".
Either use a torque wrench or be experienced enough to know what 30-foot-pounds feels like without one. A lot of the "my cranks won't come off" threads are due to corrosion or serious distortion of the square taper by the repetative torquing I mentioned.
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Old 08-21-07, 08:15 AM   #13
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I grease any metal - metal interface.
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Old 08-21-07, 09:22 AM   #14
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I recently installed a Shimano UN73 on my bike. The spindle was greased when I took it out of the box, so I'm guessing that Shimano, at least, thinks the spindle should be greased before installing the crank.
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Old 08-21-07, 09:35 AM   #15
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Quote:
Originally Posted by HillRider View Post
However, a mechanical engineer I know who is an expert on clamped interference fit parts says grease on square taper cranks is definitely a good idea. What he also says is to torque the crank to spec once when the arms are installed and then leave them alone. The damage is done by repetatively retorquing the fixing bolts which "chases" the arms up the taper until they are distorted or crack.
Jobst Brandt says the same thing:

http://sheldonbrown.com/brandt/installing-cranks.html
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Old 08-21-07, 09:43 AM   #16
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Good to know. I wasn't quoting Jobst but the reasoning was the same.
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Old 08-21-07, 11:08 AM   #17
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I greased mine. Square taper for my fixed gear bike. One shot installation. Grease crank bore, grease spindle, slide on, torque to spec, and don't fiddle with it later.
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