Advertise on Bikeforums.net



User Tag List

Results 1 to 13 of 13
  1. #1
    Senior Member
    Join Date
    Aug 2005
    Location
    New Hampshire
    Posts
    850
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    Effect of bearing precession on hub cones

    I have a theoretical question that isn't related to any specific problem I'm having, but it occurred to me as I was repacking a hub the other day.

    There are numerous threads and articles around describing what bearing precession is, especially as an explanation for why pedal and BB thread directions are reversed on opposite sides of the bike.

    My question is, does this effect apply to hub cones on threaded axles? For example, looking at my 105 rear hub from the left side, the hub shell rotates counterclockwise as the bicycle moves forward. If I'm thinking about it correctly, this would result in a slight clockwise torque on the cone. With a right-hand threaded axle, I believe this would tend to pull the cone away from the locknut. Since the only thing holding the cone in place is friction against the locknut, I would think this would create a vicious cycle where that friction force is reduced, leading to more creep in the cone, leading to even less friction, etc., while simultaneously increasing pressure against the bearings (bad).

    So, assuming I've got it right, is this ever a problem in real hubs? And if not, why is it a problem in pedals and BBs but not hubs? I would think it would make more sense to use a left-handed thread on the left side of the axle, and vice versa.

  2. #2
    Senior Member
    Join Date
    Sep 2004
    Location
    boston, ma
    Posts
    2,825
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    yes hub cones do become loose over time. whether its from precession or insufficient torque when adjusting the hub i dont know

  3. #3
    Senior Member
    Join Date
    Sep 2008
    Location
    Loveland, CO
    My Bikes
    Two LOOK 585s, one KG461
    Posts
    4,987
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    If the locknut is tightened properly, it should never be a problem. Precession forces are very small and would never loosen a cone. Very few modern hubs even use threaded cones these days - only cheap bikes with the old 10mm threaded axles.

    Some people will swear that precession forces are large enough to loosen the right side BB cup on an Italian threaded frame, but I contend that they are not. If a cup were to loosen for some other reason like the BB face not being square to the threads, or being under-torqued, those forces can eventually unscrew the cup, but not until it's fairly loose from other causes.

    The opposite situation never occurs. You don't find BB cups that have tightened themselves due to precession. If you were to hand tighten a BB cup, it will never get tight, all by itself.

  4. #4
    thompsonpost
    Guest
    Lock nuts, the clue.

  5. #5
    Senior Member
    Join Date
    Apr 2009
    Location
    New Rochelle, NY
    My Bikes
    too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
    Posts
    21,558
    Mentioned
    51 Post(s)
    Tagged
    1 Thread(s)
    As DaveSSS said these forces are miniscule, and aren't a meaningful factor in why hub bearings get loose, if they do. They're most important in pedals because of the large twisting force as the pedal spindle is flrxed back and forth with respect to the rotating crank, but otherwise can be pretty much ignored.

    Hubs where the bearing adjustment is well secured by a cone/keyed washer/locknut arrangement, or other secure system can go many thousands of miles without getting loose. Eventually they'll develop play because of wear, as will any bearing, but that's about it.
    FB
    Chain-L site

    An ounce of diagnosis is worth a pound of cure.

    “Never argue with an idiot. He will only bring you down to his level and beat you with experience.”, George Carlin

    “One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN

    WARNING, I'm from New York. Thin skinned people should maintain safe distance.

  6. #6
    bike whisperer Kimmo's Avatar
    Join Date
    Dec 2009
    Location
    Melbourne, Oz
    My Bikes
    copy/paste links: http://velospace.org/node/36949 http://velospace.org/node/47746 http://velospace.org/node/47747
    Posts
    6,824
    Mentioned
    8 Post(s)
    Tagged
    0 Thread(s)
    IMO left-hand threads on bikes are virtually pointless.

  7. #7
    Senior Member
    Join Date
    Apr 2006
    Location
    Sioux Falls
    My Bikes
    Bianchi Road bike, Nashbar Ultegra triple cyclocross, Raleigh full XT hybrid, lugged steel Schwinn, Full rigid Diamondback MTB
    Posts
    220
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Kimmo,

    I have a little experience with peddles and respectfully disagree. My kids have had issues with the peddles on their trailerbike. It seems that they were having fun peddling backwords. I didn't know it because I am usually cruising fast enough, and the trailerbike is geared low enough, that they couldn't "contribute" anyway. What they did find is that after a period of peddling backwords the pedal would fall off. Others have had this same experience with onoccupied trailerbikes. While I do understand that this probably wouldn't have happened if I had checked the torque of the pedels before the ride, I think that we would see many more people losing pedals if the left didn't have left handed threads.

  8. #8
    bike whisperer Kimmo's Avatar
    Join Date
    Dec 2009
    Location
    Melbourne, Oz
    My Bikes
    copy/paste links: http://velospace.org/node/36949 http://velospace.org/node/47746 http://velospace.org/node/47747
    Posts
    6,824
    Mentioned
    8 Post(s)
    Tagged
    0 Thread(s)
    By 'virtually' I mean completely pointless as long as the bearings aren't binding and everything's nice and tight. It could be argued the threads should be the other way round so then you know when something's wrong, cause bits fall off.

    BTW it's pedals.
    Last edited by Kimmo; 03-28-10 at 11:29 AM.

  9. #9
    thompsonpost
    Guest
    Kimmo, he got it right at least twice.

  10. #10
    bike whisperer Kimmo's Avatar
    Join Date
    Dec 2009
    Location
    Melbourne, Oz
    My Bikes
    copy/paste links: http://velospace.org/node/36949 http://velospace.org/node/47746 http://velospace.org/node/47747
    Posts
    6,824
    Mentioned
    8 Post(s)
    Tagged
    0 Thread(s)
    I'm guessing he didn't know when he was right, since he employed three different spellings.

    BTW, before anyone has a go, that comment re the threads being the other way round was kinda tongue in cheek

  11. #11
    thompsonpost
    Guest
    Yeah, I gave it a thought, too.

  12. #12
    AEO
    AEO is offline
    Senior Member AEO's Avatar
    Join Date
    Jun 2007
    Location
    A Coffin Called Earth. or Toronto, ON
    My Bikes
    Bianchi, Miyata, Dahon, Rossin
    Posts
    12,255
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    only on some raleigh bike hubs does it matter

    left side only has the single cone nut for the bearings with no lock nut.
    if you insert the wheel in backwards, the hub tightens itself to destruction.
    if you insert it in the correct way, the cone can't unwind because the fork dropouts and axle nut are holding it in place.
    Food for thought: if you aren't dead by 2050, you and your entire family will be within a few years from starvation. Now that is a cruel gift to leave for your offspring. ;)
    http://sanfrancisco.ibtimes.com/arti...ger-photos.htm

  13. #13
    bike whisperer Kimmo's Avatar
    Join Date
    Dec 2009
    Location
    Melbourne, Oz
    My Bikes
    copy/paste links: http://velospace.org/node/36949 http://velospace.org/node/47746 http://velospace.org/node/47747
    Posts
    6,824
    Mentioned
    8 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by AEO View Post
    left side only has the single cone nut for the bearings with no lock nut.
    O_O

    Sketchy...

Posting Permissions

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