Advertise on Bikeforums.net



User Tag List

Results 1 to 14 of 14
  1. #1
    Member
    Join Date
    Apr 2007
    Location
    Seattle, WA
    Posts
    27
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    crank, bolt keeps coming loose

    Hey, I'm relatively new to bike mechanics, and generally figuring it out by doing things wrong and then trying to fix them.

    I overhauled my bottom bracket about three months ago, and just last night my left crank came loose while I was riding. I'm still suspicious that someone unscrewed the bolt, because I park my bike the street, delivered to someone's door around the corner, came back, and immediately noticed the crank was wobbly. I got a socket wrench and tightened it down, but less than five minutes later the crank was loose again. I figured I hadn't tightened it properly, and tried again. Same thing a few minutes later.

    I took off my cranks today and put the bolts into the spindles without cranks and wiggled them around--the left side seems no more loose than the right, so I don't think I stripped the bolt or the inside of the spindle. The inside of the crank has wear, and slightly more on the left crank than on the right, so I'm thinking that may be my problem. Also, the washer inside the left crank won't come out anymore. It's been pretty worn for a while, but this is the first time I've been unable to get it out of the crank.

    I think that the crank is probably just worn enough on the inside that it's working itself loose. Any other thoughts? Thanks.

  2. #2
    black betty DeadSailor's Avatar
    Join Date
    Mar 2007
    Location
    florida
    My Bikes
    custom flatlandbike, trek fuel ex8
    Posts
    228
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    yea, sounds like taper on the crank has rounded out

    when you get those type of cranks its good to periodically check them to make sure theyre not loose...cuz once theyre loose theyll round out the crank and you can drag them out a bit...but eventually youll need new ones

  3. #3
    JRA...
    Join Date
    Oct 2003
    Location
    philly
    My Bikes
    trek 520 & 736, DeRosa Professional, Fuji Professional, Raleigh International 3-speed, Saronni (any info people?), Humber 3-speed, Raleigh Sports, Carlton Grand Prix coming soon!
    Posts
    839
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    did you recheck/retighten the crank after the intial installation? it's a very important step to do, and the most common cause of ruined (usually left) crankarms. cranks tend to "settle in" after installation, meaning the crank bolt is actually not as tight as it need to be any more, causing the arm to loosen and eventually wallow out on the spindle.

  4. #4
    feros ferio John E's Avatar
    Join Date
    Jul 2000
    Location
    www.ci.encinitas.ca.us
    My Bikes
    1959 Capo; 1980 Peugeot PKN-10; 1981 Bianchi; 1988 Schwinn KOM-10;
    Posts
    15,081
    Mentioned
    8 Post(s)
    Tagged
    0 Thread(s)
    Yes, do not forget that since both sides use clockwise threads, the left-side crank fixing bolt is self-loosening, like the lugnuts (lugbolts in my case) on the left side of your car.
    "Early to bed, early to rise. Work like hell, and advertise." -- George Stahlman
    Capo [dschaw'-poe]: 1959 Modell Campagnolo, S/N 40324; 1960 Sieger, S/N 42624
    Peugeot: 1970 UO-8, S/N 0010468
    Bianchi: 1981 Campione d'Italia, S/N 1.M9914
    Schwinn: 1988 Project KOM-10, S/N F804069

  5. #5
    Member
    Join Date
    Apr 2007
    Location
    Seattle, WA
    Posts
    27
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by dafydd
    did you recheck/retighten the crank after the intial installation? it's a very important step to do, and the most common cause of ruined (usually left) crankarms. cranks tend to "settle in" after installation, meaning the crank bolt is actually not as tight as it need to be any more, causing the arm to loosen and eventually wallow out on the spindle.
    i honestly don't remember at this point, but i'm aware that i should check it, and will make sure to check it next time.

    thanks for the help! time to go get a new crank, i guess.

  6. #6
    Banned.
    Join Date
    Feb 2003
    Location
    Fort Wayne, Indiana
    My Bikes
    84 Trek 660 Suntour Superbe; 87 Giant Rincon Shimano XT; 07 Mercian Vincitore Campy Veloce
    Posts
    4,766
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Hold your horses on the new crank. First try putting some Loctite Threadlocker Red on the threads, just follow the instructions on the package. This stuff could just stop the problem for way less then a new crank...unless you want to spend the jack for a new crank!

  7. #7
    Senior Member peripatetic's Avatar
    Join Date
    Oct 2004
    Location
    NYC
    My Bikes
    All 70s and 80s, only steel.
    Posts
    2,124
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Beware that aluminum crank arms are far softer than steel spindles (I'm not sure from your post if these are aluminum.) If you ride on a loose arm, even for a few street blocks, you will round out the square hole in it, and it will then be unuseable. I rode on a loose crank arm for about 5 easy miles and ended up having to replace it. If it keeps loosening on the spindle (as opposed to just the bolt), then you've probably worn it too much already.

  8. #8
    Senior Member iNewton's Avatar
    Join Date
    Aug 2005
    Location
    Baie-Comeau, Québec
    My Bikes
    Specialized Roubaix Comp '06
    Posts
    600
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by froze
    First try putting some Loctite Threadlocker Red on the threads,
    Don't use red loctite unless you never plan on unscrewing the thing.. Ever. Red is for big bolts that allows you to use either an impact wrench or huge leverage to undo.

  9. #9
    JRA...
    Join Date
    Oct 2003
    Location
    philly
    My Bikes
    trek 520 & 736, DeRosa Professional, Fuji Professional, Raleigh International 3-speed, Saronni (any info people?), Humber 3-speed, Raleigh Sports, Carlton Grand Prix coming soon!
    Posts
    839
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by iNewton
    Don't use red loctite unless you never plan on unscrewing the thing.. Ever. Red is for big bolts that allows you to use either an impact wrench or huge leverage to undo.
    a little heat fixes that. with that said, if the OP can see the deformation in the taper, chances are loctite will do little more than keep the crank bolt from unscrewing as the crankarm rocks back and forth.

  10. #10
    one and only
    Join Date
    Dec 2006
    Location
    Western Connecticut
    Posts
    63
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Sorry, but the Loctite won't help. It's not the bolts that hold your cranks on the spindle ... it's a proper press fit. Having ridden on loose cranks means that you've lost the proper press fit. As another poster noted, the soft aluminum of the cranks deforms very quickly under the load of your legs against the hard steel of the spindle. Once you've rounded the inside of the crank holes, you're done. I did that once before after not properly tightening the bolt down and riding less than 5 miles. I was never able to get the cranks on solidly after that.

  11. #11
    Senior Member peripatetic's Avatar
    Join Date
    Oct 2004
    Location
    NYC
    My Bikes
    All 70s and 80s, only steel.
    Posts
    2,124
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by s1nglespeed
    Sorry, but the Loctite won't help. It's not the bolts that hold your cranks on the spindle ... it's a proper press fit. Having ridden on loose cranks means that you've lost the proper press fit. As another poster noted, the soft aluminum of the cranks deforms very quickly under the load of your legs against the hard steel of the spindle. Once you've rounded the inside of the crank holes, you're done. I did that once before after not properly tightening the bolt down and riding less than 5 miles. I was never able to get the cranks on solidly after that.

    Yeah, I was the one who said that. Why do I get the feeling this specific post is attracting a lot of us who have learned through experience.

  12. #12
    Elitist Troglodyte DMF's Avatar
    Join Date
    Jun 2006
    Location
    Dallas
    My Bikes
    03 Raleigh Professional (steel)
    Posts
    6,896
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    You need to replace the cranks.

    Here's an interesting article on the issue: http://www.sheldonbrown.com/brandt/i...ng-cranks.html
    Stupidity got us into this mess - why can't it get us out?

    - Will Rogers

  13. #13
    Senior Member
    Join Date
    Jun 2003
    Location
    Aliwal North, Eastern Cape, South Africa
    My Bikes
    el rapido road Tandem, Raleigh R6000 Road Tandem, Omega Vectra MTB Tandem, Gary Fisher Tassajara, Carerra MTB, Trek 7200 Hybrid
    Posts
    200
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Always tighten crankbolts to the specified torgue of the manufacturer. Anything less will jeapordise the the integrity of your crankset.
    The Big H rides:
    Raleigh T6000 road tandem
    el rapido road tandem
    Omega MTB tandem
    Trek 7200 Hybrid
    Gary Fisher Tassajara

  14. #14
    Senior Member DannoXYZ's Avatar
    Join Date
    Jul 2005
    Location
    Saratoga, CA
    Posts
    11,507
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by Big H
    Always tighten crankbolts to the specified torgue of the manufacturer. Anything less will jeapordise the the integrity of your crankset.
    Yes, there's no way you can develop the proper 25-33 lb*ft of torque required by most cranks with short allen-keys of the tiny double-sided Park crank-bolt wrench. Only an automotive-style 3/8" torque-wrech with 12" handle will allow you to get that bolt tight enough.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •