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How-To/Mechanics: Looserning of drive side crank bolt

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  1.  
    • CommentAuthorsfbee
    • CommentTimeApr 22nd 2009
     
    How frequently do you find your crank bolts needing tightening?

    I've had a lot of trouble in the past with wallowing out bottom brackets and cranks in the past due to my size (6'3, 235lbs), and honestly a lack of proper maintenance. I have a set of 75's on my current bike (cranks/bb), and I'm pretty attentive about maintenance now, performing a run through of the crank and chain ring bolts with an allen wrench before and after my daily commutes.

    Lately it seems as if the drive side crank bolt needs a little tightening by the time I get home at night, which is usually after a 50 or so mile round trip commute. When tightening the bolts, I don't put all of my weight into it, but do apply a generous amount of pressure.

    My question is: Is this normal? How frequently should I really need to tighten the drive side? I've never really had problems with the drive side loosening (on geared bikes), with the left arm usually being the problematic one.

    I don't attempt to do any tricks (with the exception of the occasional attempt to ride fakie). Could the force from back pedaling when stopping and riding fakie be contributing to this?
    • CommentAuthorfilthpunx
    • CommentTimeApr 22nd 2009
     
    they should never come loose if you tighten it good enough unless something is stripped/ worn out.put a little BLUE locktite on it if it keeps it up and itll be fine
    • CommentAuthorgreg
    • CommentTimeApr 22nd 2009
     
    Put some grease on them if you haven't already and then crank down - the grease will help the threads engage a little bit more and chances are it will fix the problem (if you haven't already done this)
  4.  
    Find someone with a torque wrench and make sure you're tightening them enough. I was amazed how tight they're supposed to be the first time I actually used one. Now if I have a wrench that's maybe 8 inches long, I know to just tighten the bolt as tight as I can get it. After that I never have them coming loose. I'm only 140 lbs, but still, we're not bouncing around on these things standing up like on a bmx bike. All the weight going down on a fixed gear should be evened out by how hard you're pulling up, so even though I'm only 140, the top half of me is tiny, and most of the weight is my legs from riding a bike.

    Does the crank arm actually come loose, or just the bolt? If the whole crank arm is coming loose you might want to check the taper, after you've ridden on a loose crank arm so long, the taper tends to get worn down and there's no amount of tightening that'll ever keep the crank arm on.

    A 50 mile round trip commute huh? That sounds pretty intense.
    • CommentAuthorsfbee
    • CommentTimeApr 22nd 2009
     
    I'm probably gonna pick up a torque wrench when I get out of the office tonight, as I've been using an allen wrench from a cheapo auto toolkit up until this point. I had them professionally installed, and the guys who installed them have a pretty good rep, so I'm sure they applied the appropriate torque. I'll definitely apply either the locktite or grease when I do this, or may just drop it by the shop that installed them if I get the chance

    The cranks should be fine. I'm real paranoid about my bolt tightness based on experiences with previous setups, so I've been obsessively attentive with this set from the start. When the bolts are loose, it's not so loose that I feel it in the cranks, just loose enough that I can apply further tightening with only a little bit of pressure

    Thanks for the input guys

    Posted By: upthemaidenA 50 mile round trip commute huh? That sounds pretty intense.


    Yup, that's a round about figure. 15 miles door to door from home to office, but I usually head out an hour early and do some riding around parts of the city. I live in Houston, so everything is really, really spread out with no hills, so it's not too bad. I'm thinking about doing my first century fixed this weekend, if the current weather conditions persist (and if my cranks don't fall off first, heh)
  7.  
    That doesn't sound as bad. Where I live you're either climbing up a hill for 10 minutes, or shooting down the other side for 2, then back up another.

    Also I forgot to say that you should check your bottom bracket spindle. Did they grease it before the crank arms went on? Some people will argue both sides of this, but considering it's a tapered fit, you should not be greasing the spindle and crank arm(except for the crank bolt threads, which should be greased). Greasing the spindle before tightening the cranks on gives it less resistance, and a better chance that your crank arm will slide on farther than it should, and could stretch the taper, and would also make it easier for the crank arm to slide off slightly as well. I'm sure plenty of people here can say "I always grease my spindle and my crank arms never come loose!", but that's how it is
    • CommentAuthorgreg
    • CommentTimeApr 22nd 2009
     
    Oh, I thought we were talking about chainring bolts. Don't grease your tapers, grease your crank bolts and chainring bolts liberally and often
    • CommentAuthorsfbee
    • CommentTimeApr 22nd 2009
     
    Nah, The chain ring bolts have been fine so far. I just include checking them in my daily routine to be safe. So far, the cranks bolts have been the only problem, in the fact that they loosen up more than I'm comfortable with
    • CommentAuthorOtto Rax
    • CommentTimeApr 22nd 2009
     
    are the cranks and spindle the same taper?
    • CommentAuthorsfbee
    • CommentTimeApr 22nd 2009 edited
     
    Yea, both the cranks and bb are SG75, so that shouldn't be an issue (I would hope :)
  12.  
    A greased taper will crack your cranks if you tighten them to spec. Never grease a spindle.
  13.  
    i have a problem wtih my bottom bracket but mine is on the non-drive side. i'm a similar size (6'4", 205) and have 175s. my bottom bracket (only 6 mo. old) clicks on the non-drive side (left arm) when i'm applying alot of pressure (fakie, stands) or alot of torque when pedaling hard. it's definitely not my chain ring or my pedals. is it possible that the non-drive side is too tight? i don't mean to hijack the thread but while we're on the subject...
    • CommentAuthorsfbee
    • CommentTimeApr 22nd 2009
     
    My first guess would be it's from the frame flexing, but I'm probably wrong
    • CommentAuthorfilthpunx
    • CommentTimeApr 22nd 2009
     
    could be to tight, or maybe too loose?, my bottom bracket did the same thing before when it was loose
  16.  
    Most of the time that grindy click sound is due to a worn bb, or cups that are not tight in the frame.

    Also, when it comes to bearings, always remember a hair loose is better then too tight.
  17.  
    I'd pull out your bottom bracket, clean everything, regrease, and put it back together. one of my bikes has been clicking when push down on the drive side pedal, but only if it's after I've pushed on the non drive side, if I push on the drive side, then let the non drive side pass, then push on the drive side again it doesn't creak, so it means something is shifting back and forth. I've just been too lazy to pull it apart and mess with it since my basement is currently a mess.
  18.  
    Maiden that sounds like a pedal.
    • CommentAuthorhenrydec1
    • CommentTimeApr 22nd 2009
     
    put a little locktite on them and if they keep going bad they may be striped out.
  20.  
    Locktite!? Locktite is never a solution for ANY part on a bicycle. Fix the problem, don't put a bandaid on it. If something will not stay tight, then there is a problem with it.
  21.  
    Oh shit. I am harassing someone who lives in my zip code. Even so. I stand firm in my argument that locktite has no place on a bicycle. Where bouts you livin henry?
    • CommentAuthorlatron
    • CommentTimeApr 22nd 2009 edited
     
    Posted By: hardsole5280A greased taper will crack your cranks if you tighten them to spec.


    Hmm. I guess I've been doing everything wrong -- greasing tapers, yet never cracked a crank. So I'm not tightening the bolts to spec? Anyway, still alive -- and my bolts stay put.
  23.  
    Google it bro. Check selton brown- its all over. Spindles shold not be greased. But I am very, very happy for you.
  24.  
    And how would a greased taper have anything to do with the bolt staying on?
    • CommentAuthorlatron
    • CommentTimeApr 22nd 2009 edited
     
    Clearly I'm the wrong one to ask. :) (Actually, this was a reference to the original comment; I've never had this problem, for what it's worth.)

    Re Sheldon Brown, I looked and found this: http://sheldonbrown.com/brandt/installing-cranks.html. Perhaps the author doesn't count as Sheldon himself, so one should disregard?
  26.  
    Barnett, campy and shimano all recommend no grease on square taper bottom brackets. The only one who does is race face, and they claim to compensate for grease in the machining of their cranks.

    I have seen 2 non drive cranks crack on the back side, and have seen cranks suck up so far the bolt would not hold them tight.

    But I don't really know anything about bikes.
  27.  
    I thought it was the pedal at first, but if it was then it would creak every time around whether I put pressure on the other side or not. I figure it must be the bottom bracket because it only makes the noise when I alternate between pressure on both sides, meaning that something is moving when I push on the non drive side that effects the drive side making a noise, and that wouldn't have anything to do with the pedal.

    Loctite works well on rack mounting bolts. A lot of other random parts come from the factory with loctite on them as well, like the bolts that hold disc brake calipers and disks, but I don't recommend putting it everywhere. I never understand why so many people feel the need to loctite their cogs onto their hubs when I put grease on mine just to make sure they don't get stuck. Then their cog needs replaces and they're fighting with it for a week and giving you that stupid face that says "why is my life so difficult?!"

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