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Cranks coming loose....

Discussion in 'The Shop' started by stosh, Sep 23, 2005.

  1. stosh

    stosh Darth Bailer

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    So is there anyway to stop my cranks from coming loose from my square BB?
     

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  2. Urban FR'er 666

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    Remove the nut or bolt, extract the crank, clean any grease off the spindle including inside threads(bolt type), and in the crank, and on the bolt(or in the nut). Then put the crank back on, the spread "RED LOCTITE"(not the common blue) on the threads. Reinstall the nut/bolt, a little tighter than usual, and don't ride it for 24hours(for the loctite to set to maximum strength).
     
  3. stosh

    stosh Darth Bailer

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    Ok cool thanks man!!!
    I was worried about putting locktight on the threads though.
     
  4. Jeff 151

    Jeff 151 Monkey

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    Cranks in good order should stay tight with just grease. Check that the square holes in the arms aren't deforming, as they will when ridden loose. If they are, then pitch 'em. Red loctite is typically for stuff you never plan on unscrewing. 242 (blue) is more appropriate. Cranks go on balls tight so use a torque wrench to make sure you're gettin' up there.
     
  5. Grizzle

    Grizzle Monkey

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    Whoah, im not so sure thats totally correct. I believe for a square taper crank you should have absolutely NO grease ANYWHERE on the spindle, and only a very small amount on the bolt that holds the arm on the bottom bracket. If you get grease on the square taper, it will oval out. The square taper works off friction, grease is the enemy of friction. And you should not need to tighten that bolt to more than 50 ft/lbs.
     
  6. binary visions

    binary visions The voice of reason

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    Yeah, square taper cranks shouldn't have grease on the spindle.

    A little bit of blue loctite on the crank bolt will do one of two things:

    A) keep the cranks from coming loose again, or
    B) tell you that it's time for new cranks or a new BB. Square tapers that are constantly coming loose have often given up the ghost.

    Red loctite really doesn't belong anywhere near a bike, since you always want to be able to get the part back off again.
     
  7. stosh

    stosh Darth Bailer

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    Ok cool I have some blue locktight at home so I'll throw some on and clean off the spindle.
     
  8. Urban FR'er 666

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    Red Loc-tite can be used on threads of steel-steel(and it can be removed, it isn't as "PERMINANT" as they claim), and the place you would only want to use blue is a steel bolt in an aluminum item...
     
  9. Jeff 151

    Jeff 151 Monkey

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    Grizzle, I know you don't grease a 4-taper spindle. I didn't say you did. But I see where you read me wrong. I meant cranks should stay tight with grease, not loctite on the hardware threads.
     
  10. Grizzle

    Grizzle Monkey

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    Sorry jeff, guess i read your post wrong. I just wanted to clarify that to him, i have had people put grease on them before, and it is bad news bears in a hurry.
     
  11. maxyedor

    maxyedor <b>TOOL PRO</b>

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    typicly the crank will wallow out then ruin the spindle so naturaly if you nreplace just one part the other will ruinthe new part in a hurry if a dab of loctite doesn't work chuck 'em both and get some profiles they will positivly never loosen break or fail in any way
     
  12. Mackie

    Mackie Monkey

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    Not really. This is one of the age old debates that rages over in esoteric corners of the web like rec.bicycle.tech. Some manufacturers would recomend grease (Race Face) others would say to stay away from it (Shimano, Campy). In the end, the story is that it does not really matter if you grease tapers or not. Park says it's not needed, but they don't say it will harm the cranks.

    Inadequate tightening in initial installation is what causes crank holes to get a little out of square - the soft aluminum can move slightly on the hard steal and you end up with an out of spec hole. After that, you need loctite or other fixes to keep things snug.

    Here's what Jobst Brandt says, over on Sheldon Brown's website:

    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.
     
  13. BMXman

    BMXman I wish I was Canadian

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    I use to always grease square tapers and never had a problem all you need is a torque wrench.. and a little grease...but it really depends on how old and in what shape the cranks are in....my advice would be to ditch them. There are much better set up's out there now days...D