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Discussion Starter · #1 ·
Everytime I decide I should try a new style BB (Octalink/ Isis) I hear another story about bearing failures - back to square taper. Problem is I get occasional creaking & loosening crank bolts. I have installed the cranks dry per Park tools instructions & lubed per my LBS's method - which do you do and why? Should I try a loctite on the crank bolts or not? Thank you
 

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Derailleurless
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Here's the book I wrote: Most important factor is proper torque. Second most important factor is lube on the spindles (I prefer anti-sieze lubricant).

Torque helps to ensure a proper balance between the crank fixing bolt stretching and developing the tension that holds the crank in place, versus the elastic deformation of the crank's square taper interface that prevents it from riding any further up the spindle. Too loose, and the crank rides up the spindle on its own (under pedaling torque) causing the bolt to lose tension and even allowing it to back out.

Lubricant does nothing more than to preserve the interface by preventing galling of the machined surfaces during the installation process, acting as an anti-corrosion layer between the aluminum crank arm and steel or titanium spindle, provides for consistant forces (as measured by the torque wrench) over the course of repeated installations, and assists in easy crank extraction.

LocTite is unnecessary. Proper torque resulting in sufficient tension should hold the crank fixing bolt in position without any aide from threadlockers.

Shimano specs proper torque at around 35 ft-lbs; other brands are in a similar range. Without a torque wrench, sometimes this feels like "too much", that's you've gone too far and are stripping or damaging something. Fact is, it just takes a long time to build up to full torque, because unlike a normal bolt application where you're fastening against something hard, in the case of a square taper crank installation you are slowly walking the crank interface up the taper, resulting in a prolonged build-up to proper torque.

As an aside, I've been running Octalink for a few years now and the bearings have held up fine. I don't read about many Octalink bearing failures, but the ISIS stuff does seem a bit abundant. Octalink cranks seem even more likely to work loose if not torqued correctly, but once they are fastened up per manufacturer's spec, they stay tight and present no notable problems.
 

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trail waggler
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Definitely it's all about torque...

As the 'feller above said, get a torque wrench, set it to 35 ft./lbs., and tighten both crank bolts. If I install a new crank, I have to do this after every ride for about a month, then I just check it once a month. BTW, if you use a click type wrench, back it off to 0 for storage, so the the spring won't tend to take a 'set', and change the calibration.

I have had no problems with square taper bottom bracket/cranksets, except for what to do with all the money I saved over buying the 'latest & greatest' :)
 

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keen said:
I have been running 30lbs. of torque - i'll try 35lbs. and see if that does the trick. Thanx
So I'm sure you know the drill already, but it bears repeating: if the taper has been ridden loose and has rounded, you may as well make it a paperweight or find a way to permanently affix it to the spindle (JB Weld, anyone?).
 

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Discussion Starter · #6 ·
Speedüb Nate said:
So I'm sure you know the drill already, but it bears repeating: if the taper has been ridden loose and has rounded, you may as well make it a paperweight or find a way to permanently affix it to the spindle (JB Weld, anyone?).
I had the arms off the other day and everything is like new. I just have to decide if I should continue using the Truvativ 5D's or use my Deore Hollowtech's? maybe they are of the same quality? Thanx
 

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"El Whatever"
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So far...

I've had problems with square tapers but not on Octalinks.

I don't have a torque wrench (just too expensive down the border) though I'd like to have one... but that only backs up my preference on octalinks. They do not need a careful adjustment.

Best thing to do here is not to touch the cranks if they don't need to.
 

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"El Whatever"
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Had you tired to buy one in Mexico???

Guess you don't. I could buy a new crankset for the price of a torque wrench.

Don't get me wrong... I'd like to get one. I've been working on installation of Gas Turbines and pretty much know the importance of the thing (especially with alloy Inconel bolts)... it's just that prices here are ridiculous...

If I could have at home the tools I had on Site... dude, my bike should be running even smoother than it does... I whish I could have a dial indicator to work on my rotors but down here those are around 150 bucks (the price of three rotors).
 

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MTB Rider
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Blue Loc-Tite Can't hurt anything!!!!

Speed?e said:
Here's the book I wrote: Most important factor is proper torque. Second most important factor is lube on the spindles (I prefer anti-sieze lubricant).

Torque helps to ensure a proper balance between the crank fixing bolt stretching and developing the tension that holds the crank in place, versus the elastic deformation of the crank's square taper interface that prevents it from riding any further up the spindle. Too loose, and the crank rides up the spindle on its own (under pedaling torque) causing the bolt to lose tension and even allowing it to back out.

Lubricant does nothing more than to preserve the interface by preventing galling of the machined surfaces during the installation process, acting as an anti-corrosion layer between the aluminum crank arm and steel or titanium spindle, provides for consistant forces (as measured by the torque wrench) over the course of repeated installations, and assists in easy crank extraction.

LocTite is unnecessary. Proper torque resulting in sufficient tension should hold the crank fixing bolt in position without any aide from threadlockers.

Shimano specs proper torque at around 35 ft-lbs; other brands are in a similar range. Without a torque wrench, sometimes this feels like "too much", that's you've gone too far and are stripping or damaging something. Fact is, it just takes a long time to build up to full torque, because unlike a normal bolt application where you're fastening against something hard, in the case of a square taper crank installation you are slowly walking the crank interface up the taper, resulting in a prolonged build-up to proper torque.

As an aside, I've been running Octalink for a few years now and the bearings have held up fine. I don't read about many Octalink bearing failures, but the ISIS stuff does seem a bit abundant. Octalink cranks seem even more likely to work loose if not torqued correctly, but once they are fastened up per manufacturer's spec, they stay tight and present no notable problems.
I messed around with a crank for months. The LBS was supposedly using the proper tools and the damn thing kept creaking and the bolt kept loosening. I finally got pissed off and put the right allen screw on a 14" wrench and went to to on that SOB. I also slathered blue LocTite all over the threads. I haven't heard a peep out of them since. They don't wan the dreaded wrench anymore ;-)

We shouldn't have to check our crank bolts AT ALL!!!!! This is like having to check your lug nuts. They should be tightened properly in the first place and STAY THERE!!!!!!
 

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willtsmith_nwi said:
I messed around with a crank for months. The LBS was supposedly using the proper tools and the damn thing kept creaking and the bolt kept loosening. I finally got pissed off and put the right allen screw on a 14" wrench and went to to on that SOB. I also slathered blue LocTite all over the threads. I haven't heard a peep out of them since. They don't wan the dreaded wrench anymore ;-)

We shouldn't have to check our crank bolts AT ALL!!!!! This is like having to check your lug nuts. They should be tightened properly in the first place and STAY THERE!!!!!!
Suit yourself. If's a self-fulfilling prophecy, you know -- install 'em loose, run 'em loose, and they'll keep loosening up. Tighten 'em up right the first time -- torque wrench and all -- and they'll stay put.

I'm glad you finally got yours settled into place, but the thought of Loctite slathered on anything.... brrrr -- sends shivers up my spine!
 
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