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self extracting crank arm bolts...

jonKranked

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Nov 10, 2005
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Ok... so I have an old set of XTR cranks that have Shimano's old self extracting bolts. The system is on an octalink BB. I was wondering if it is possible to replace the self extracting bolts with stand crank arm bolts (and if anyone has done this)? I get an odd creaking from the cranks occasionally when I pedal; I have tried a diff BB to no avail. This is about all I can think of that would cause it - other than the splines on the crank arms themselves being worn out.

Thoughts?
 

Dartman

Old Bastard Mike
Feb 26, 2003
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Richmond, VA
The only part that makes them self extracting are the rings screwed into the dust cap threads and they don't come into play when the bolts are tight. When you unscrew the bolts they push against the rings to remove the crank. Other than that they are just regular bolts.

You could try removing the rings and their washer with a pin spanner to see if they are causing the squeak. It's important for the washers to be there so the bolt slips easily against the ring.

I'd take everything apart and give it a good cleaning, use teflon tape on the BB threads and then lube the BB splines and install the cranks. Use a torque wrench to 35-40ft/lbs on the bolts.

Check the chainring bolts too. Might want to do that first since it's easy. :p
 

jonKranked

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Nov 10, 2005
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The only part that makes them self extracting are the rings screwed into the dust cap threads and they don't come into play when the bolts are tight. When you unscrew the bolts they push against the rings to remove the crank. Other than that they are just regular bolts.

You could try removing the rings and their washer with a pin spanner to see if they are causing the squeak. It's important for the washers to be there so the bolt slips easily against the ring.

I'd take everything apart and give it a good cleaning, use teflon tape on the BB threads and then lube the BB splines and install the cranks. Use a torque wrench to 35-40ft/lbs on the bolts.

Check the chainring bolts too. Might want to do that first since it's easy. :p
word. thanks for the heads up y'all. I'll also check the spider... since its one of the ones that's bolt on.
 
Strip it/ clean it. Don't use tefflon tape. Greasethe threads, and spline. If it is square teper do NOT put grease on the taper. Check the frame for cracks around the welds especially at the BB area. Remove the pedals and lube the threads there too. If they are clipless pedals squirt some tri-flow on the springs. If the BB is Octalink make sure it is not wasted, chances are it is.
 

Dartman

Old Bastard Mike
Feb 26, 2003
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Richmond, VA
If it is square teper do NOT put grease on the taper. .

Subject: Installing Cranks
From: Jobst Brandt

My cranks get loose, quite quickly too; over about 10 miles or so from being solid to flopping about in the breeze. Any suggestions?
One or both of the cranks are ruined!* Once ridden in the "floppy" mode, the tapered square bore of the crank has been deformed and can no longer be secured on a spindle. Install and properly tighten new cranks on the spindle after greasing the tapered square ends of the spindle. Proper tightness should be achieved with a torque wrench or by a skilled hand.
The admonition not to grease the spindle finds life mainly in the bicycle trade. When I discussed the "dry assembly" rule with crank manufacturers, I discovered that they had warranty claims from customers who split cranks. However, cranks cannot be split by overtightening them. This can be proven by attemting to do so. An M8x1 bolt is not strong enough to split a major brand crank.
Failure from "over-tightening" is caused by repeated re-tightening of properly installed cranks. In use, an aluminum crank squirms on its taper and, because the retaining bolt prevents it from moving off the taper, it elbows itself away from the bolt and up the taper ever so slightly. The resulting loss of preload, after hard riding, can be detected by how easily the bolt can be turned.

Loss of crank bolt preload is greater on left than the right cranks, because left cranks transmit torque and bending simultaneously while right cranks transmit these forces separately. The left crank transmits driving torque through the spindle to the right crank and chainwheel while the right crank drives the chainwheel directly. Besides that, the right crank transmits torque to the spindle only when standing on both pedals. Doing this with the right foot forward (goofy footed) is the only time the spindle transmits reverse torque.

Mechanics, unaware of why crank bolts lose preload (and commensurate crank tightening), have re-tightened bolts until cranks split. No warnings against re-tightening properly installed cranks are evident although it is here where the warning should be directed rather than at lubrication.

Because friction plays no role in torque transmission, preload in the press fit must be great enough to prevent elastic separation between the crank and spindle under torque and bending. This means that no gap should open between crank and spindle facets under forceful pedaling. Crank bore failure occurs when the press fit is loose enough that a gap opens between spindle and crank. Torque is transmitted by both leading and trailing half of each facet, contact pressure increasing and decreasing respectively. In the event of lift-off, the entire force bears only on the leading edge of facets and causes plastic deformation, causing the bore takes on a "pin cushion" shape (loose crank syndrome). Subsequent tightening of the retaining screw cannot correct this because neither the retaining bolt nor crank are strong enough to re-establish the square bore.

The claim that a greased spindle will enlarge the bore of a crank and ultimately reduce chainwheel clearance is also specious, because the crank cannot operate in a plastic stress level that would soon split the crank in use. However, increased engagement depth (hole enlargement) may occur without lubricant, because installation friction could ream the hole.

With or without lubricant, in use, cranks will make metal-to-metal contact with the spindle, causing fretting erosion of the steel spindle for all but the lightest riders. Lubricating the spindle for assembly assures a predictable press fit for a given torque. Without lubrication the press is unknown and galling (aluminum transfer to the steel spindle) may occur during assembly. After substantial use, spindle facets may show rouge and erosion from aluminum oxide from the crank, showing that lubricant was displaced.

Crank "dust caps" have the additional duty to retain loose crank bolts. Because crank bolts lose preload in use, they can become loose enough to subsequently unscrew and fall out if there is no cap. If this occurs, loss of the screw will not be noticed until the crank comes off, after the screw is gone.
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jonKranked

Press Button, Receive Stupid
Nov 10, 2005
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If it is square teper do NOT put grease on the taper.
...

The system is on an octalink BB.

:lighten:

If the BB is Octalink make sure it is not wasted

I have tried a diff BB to no avail.
It was a brand new BB that I tried, so that eliminates that possibility.


Check the frame for cracks around the welds especially at the BB area.
Frame is fine, I didn't have this problem when I had other cranks installed on the frame, but I had this problem when I had these cranks installed on other frames, just now getting around to addressing it.


Thanks for the advice tho :thumb:
 

binary visions

The voice of reason
Jun 13, 2002
21,695
498
NC
My experience with the Shimano Octalink bottom brackets is that they are very prone to creaking unless you over-tighten them. I know it's not good practice, but I usually just torqued the hell out of the bottom bracket and it would go away. Came up with no other solutions, and believe me, I tried. Regular tightening of the BB was the solution.

That's from 3 different frames and 2 different sets of Octalink BB/cranks. The self-extracting crank bolts are not the cause since they went missing for one of the installations and I used another set. As a matter of fact I never found a loose crank bolt to be the cause, it was always the bottom bracket backing out a little.

Doesn't really help, I know, but at least you know you aren't the only one who has seen the problem :p
 

Dartman

Old Bastard Mike
Feb 26, 2003
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0
Richmond, VA
I have that same XTR crank setup on my M1. I had swapped out the BB for the original XTR octalink BB with the lock ring on the left side. It has deeper threads for the chainguide boomerang. It has never creaked. I'm the only thing creaking on the bike. :p

Unfortunately they are very hard to find now if not impossible.