What's that occasional thunking?

Discussion in 'Cycling Equipment' started by diehard, Apr 16, 2007.

  1. diehard

    diehard New Member

    Joined:
    Apr 14, 2007
    Messages:
    14
    Likes Received:
    0
    I'm a returning, tentative rider of a new Electra Townie 7-speed and have been feeling a sporadic thunking sound associated with the pedals. The bike shop guy rode it around the block and didn't notice anything. Could it be the rider and not the bike? PD causes one side to be less efficient than the other, i.e., my left foot drags. Could uneven pedalling be causing this. (I say "thunking" rather than "clunking" because I feel it in my body more than hearing a metallic sound.) Thanks.
     
    Tags:


  2. Darkhorse85

    Darkhorse85 New Member

    Joined:
    Mar 23, 2006
    Messages:
    31
    Likes Received:
    0
    does the 'bump' occur in the same place through your pedal rotation every time? even when you change gears?

    i have that exact problem...on a fairly new bike nonetheless [​IMG]
    It must be either the chain, the bottom bracket, or the pedals.
     
  3. bobbyOCR

    bobbyOCR New Member

    Joined:
    Aug 31, 2005
    Messages:
    1,357
    Likes Received:
    0
    It could be your saddle height. I'm by no means an expert in biomechanics but incorrect position, especially seat height and fore-aft position of the saddle can create some major problems with your leg joints.
     
  4. diehard

    diehard New Member

    Joined:
    Apr 14, 2007
    Messages:
    14
    Likes Received:
    0
    Thanks, Darkhorse85. I'll suggest these areas be looked at when I bring it in. It really helps not to go in empty-handed. Interesting that your bike is also new.
     
  5. diehard

    diehard New Member

    Joined:
    Apr 14, 2007
    Messages:
    14
    Likes Received:
    0
    P.S. Although I haven't carefully tracked it, yes, it seems to be occurring in the same place.
     
  6. diehard

    diehard New Member

    Joined:
    Apr 14, 2007
    Messages:
    14
    Likes Received:
    0
    Although a "body scan" was employed for correct fit, the seat has been adjusted up and down, so that's worth checking. Maybe when it's right, I'll mark the spot with an indeliible marker. Thanks for the idea.
     
  7. Insaneclimber

    Insaneclimber New Member

    Joined:
    Aug 21, 2006
    Messages:
    158
    Likes Received:
    0
    I think it would be unlikely to be you knee or hip. one possibility i can think of is that maby the free hub aint tight, and it turns slightly under load. which is normal on a new bike. As we say in maintenance, if you cant see whats wrong with it. just keep going till it realy breaks. Then youll know.
     
  8. diehard

    diehard New Member

    Joined:
    Apr 14, 2007
    Messages:
    14
    Likes Received:
    0
    Hi Insaneclimber. Is "Wait till it really breaks..." the same as "If it ain't broke, don't fix it (yet?) I think I'm out of my league. I can imagine "it" eventually breaking as I go flying off my bike, knowing finally what he problem really was. Still, I'm glad to know you don't think it's me that's causing it. Thank you.
     
  9. John Knees

    John Knees New Member

    Joined:
    Aug 31, 2004
    Messages:
    115
    Likes Received:
    0
    I notice that nobody so far has suggested checking the fit/tightness of the cranks on the bottom-bracket axle, for "float" in the bottom bracket itself, or even for a loose bottom-bracket cassette.

    If either crank isn't really tight on the axle, this will always manifest itself at the left crank, for obvious reasons.

    You can check for float in the bottom bracket by getting a mate (or bike-stand) to hold the bike while you rock either crank at right-angles to the plane of the b.b. axle. This will also show up whether the b.b. cassette (if you have one) needs a slight graunch with a spanner.

    Anyway it's always a good idea to run over the bike with spanners, Allen keys and screwdrivers at least once a week, and especially if you've just re-built it.

    Totally off the topic, I recall that many years ago Barry Hoban had appalling knee problems. They went on for weeks, and were finally tracked down to a a minutely out-of-plane pedal spindle.

    As the old song says, "little things mean a lot".

    Good Luck

    :eek: John :eek:
     
  10. diehard

    diehard New Member

    Joined:
    Apr 14, 2007
    Messages:
    14
    Likes Received:
    0
    Dear John. I'm impressed by the depth of your analysis on the basis of my somewhat vague description. This is great ammo to bring to the bike shop next week. I'll report back once I know something. Thanks for taking the time to respond.
    M
     
  11. Darkhorse85

    Darkhorse85 New Member

    Joined:
    Mar 23, 2006
    Messages:
    31
    Likes Received:
    0
    john, youre right!


    i just came back to this thread to report that i discovered that my bottom bracket was loose, and that is what was causing the thump. i can almost wiggle the crank arm in and out. under close inspection, it's the actual bottom bracket sealed cartridge itself which is moving.

    ...now all i gotta do is find out how to tighten it...

    from wikibooks:
     
  12. John Knees

    John Knees New Member

    Joined:
    Aug 31, 2004
    Messages:
    115
    Likes Received:
    0
    I must tell this "I was a pratt" story.

    I built my first "real racer" in 1947/48 ("One piece at a time", as per Johnny Cash) based on a 1939 Dawes frame. I was 14 at the time.

    Lubrication to head, hubs and bottom bracked was by grease gun: once you saw grease exuding, you stopped.

    Each week the head (2 nipples) and hubs got a pump or two, but the bottom bracket always seemed to need more before the little tell-tale snot appeared where the axle poked out.

    About three years later I decided to re-paint the frame. I stripped everything down, and took the paint off with a paraffin blowlamp (not too hot a flame). As I started burning the paint off the seat tube, there was a frying noise, and a large sausage of grease appeared in the bottom-bracket void.

    I salvaged this and carried on: more grease appeared, and more, and more, and the same thing happened with the down tube.

    Because the bottom bracket was open to both seat and down tubes, that's where the grease had been going - about a pound up each tube.

    Yer live and learn!

    :confused: John :confused:
     
  13. Insaneclimber

    Insaneclimber New Member

    Joined:
    Aug 21, 2006
    Messages:
    158
    Likes Received:
    0
    Didn't you say the mechanic at the bike shop tested it, that guy must be a moron, i wouldn't go there again.
     
  14. John Knees

    John Knees New Member

    Joined:
    Aug 31, 2004
    Messages:
    115
    Likes Received:
    0
    My old Dad used to say "Well boy, there's mechanics and there's muckanics...." - a fancy overall with a logo over the pocket doesn't always mean membership of the first group.

    :) John :)
     
  15. diehard

    diehard New Member

    Joined:
    Apr 14, 2007
    Messages:
    14
    Likes Received:
    0
    Dear Insaneclimber and Darkhorse,

    I don't believe I said he was a mechanic. He helped me when I was test-riding it and outfitting it before purchase; he also adjusted the fit. He is in no way a "moron," He just didn't experience the "thunking" when he rode it around the block, and it would be uncivil to call him that even if it were true.
     
  16. diehard

    diehard New Member

    Joined:
    Apr 14, 2007
    Messages:
    14
    Likes Received:
    0
    Thunking appears to be caused by the rider, not the bike. As I suspected, uneven pedaling is the culprit. Thanks anyway.
     
  17. diehard

    diehard New Member

    Joined:
    Apr 14, 2007
    Messages:
    14
    Likes Received:
    0
    Hi Drkhorse,

    Thunking appears to be caused by the rider, not the bike. As I suspected, uneven pedaling is the culprit. Thanks anyway.
     
  18. diehard

    diehard New Member

    Joined:
    Apr 14, 2007
    Messages:
    14
    Likes Received:
    0
    Thunking appears to be caused by the rider, not the bike. As I suspected, uneven pedaling is the culprit. Thanks anyway.
     
  19. diehard

    diehard New Member

    Joined:
    Apr 14, 2007
    Messages:
    14
    Likes Received:
    0
    Thunking appears to be caused by the rider, not the bike. As I suspected, uneven pedaling is the culprit. Thanks anyway.
     
Loading...
Loading...