front wheel now has wicked shimmy

Discussion in 'Cycling Equipment' started by BicyclingGuitar, Aug 17, 2009.

  1. BicyclingGuitar

    BicyclingGuitar New Member

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    Since the early 1980s I've ridden my 1977 Schwinn ten-speed many tens of thousands of miles "no-hand" while playing guitar in traffic day and night, up hills, from one town to the next and back nonstop, to stores, restaurants, etc.

    Last November I made the mistake of riding WITHOUT a guitar. Somehow my front wheel hit a curb or something and bent the rim. The LBS straightened it, but lately my front wheel has developed a wicked shimmy. It whips sideways back and forth faster and faster making it less safe for me to ride with no hands playing guitar.

    I checked the tire's air pressure first. It's good. I also don't think the front fork is bent. There are no scratches in the paint or deformations of the front fork to indicate any damage has been done to it. I had the front wheel hub rebuilt with all new bearings and fresh Phil Wood waterproof grease. When I hold up the bike and spin the front wheel, it looks straight. However, something is evidently wrong.

    It seems worse when I have cargo on the rack over the rear wheel. This may be taking some of the weight off the front wheel, but why is it shimmying? It didn't use to. Any ideas anyone?

    When I can afford it I plan to have new wheels built using vintage Schwinn Approved quick release hubs and new Sun CR-18 27" rims. Until then, if the shimmy on the existing front wheel can't be fixed, I will switch back to the original bolt-on front wheel that came with my bike.
     
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  2. BicyclingGuitar

    BicyclingGuitar New Member

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    I've done some research. The late great Sheldon Brown has an article about shimmy written by someone else posted on his site. There are other sites too. There seems to be some confusion or controversy over the cause, but one possible culprit may be a floppy unsupported cargo on the rear rack.

    Now that I think about it, the worst shimmying happens when I put my bookbag containing my Pignose amplifier and instrument cable on the back rack. I haven't had as much trouble carrying groceries and such there probably because they are secured more tightly.

    For the time being I think I'll keep the wheel I have and be more careful to tightly secure cargo on the rack. It was interesting to note the multitude of theories online about the cause of bicycle shimmying. I hadn't encountered it on my bicycle until recently, even though I've been riding the same bicycle the same way (while playing guitar) since the early 1980s.
     
  3. alfeng

    alfeng Well-Known Member

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    A damaged/bent fork is difficult to discern by simply eyeballing it ...

    The next time you have your bike outside, put your hand on the saddle and WALK your bike forward (on level ground) ... if the front wheel flops to one side or the other (presuming you are coordinated enough to walk along side your bike while only holding onto the saddle vs. the handlebars), then the fork was damaged when you ran into the curb OR at some other point in time.

    Try walking someone else's bike, too, just to confirm that the wheel isn't flopping because you are a klutz.
     
  4. BicyclingGuitar

    BicyclingGuitar New Member

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    I just tried walking my bike while holding the saddle. It isn't quite level where I live. The wheel eventually flops to one side or the other, but not consistently. I will try tomorrow at the LBS and try walking one of the bikes there.

    The shimmying problem only started in the past month or so, and I had ridden before then since the incident in November without any problems. I do hope my fork isn't bent! If it is, do I need a new one or can it be straightened somehow? My bicycle has a tubular fork so I'm not sure how that can be straightened...
     
  5. alfeng

    alfeng Well-Known Member

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    Theoretically, a bent fork can be straightened ...

    When a steel fork is made, it is often tweaked by the guy who brazed it ...

    So, while an LBS might be able to straighten a fork, it is something that should be done by a framebuilder.

    The "problem" is that it might be less expensive to simply buy a replacement/new fork UNLESS there is something historical about the fork which warrants spending the money on aligning it.
     
  6. BicyclingGuitar

    BicyclingGuitar New Member

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    The fork is of historical value, being part of the frame of the one bicycle I've been riding for nearly thirty years while playing guitar. However, a more likely suspect has been found: the spokes of my rear wheel badly need tightening.

    I have an appointment first thing tomorrow when the LBS opens. Hopefully this will resolve the issue. My bike should ride smoothly again then, especially since it turns out the front hub I recently had rebuilt trying to solve this problem DID need to be rebuilt. Tomorrow the LBS guy will also use a tool to check the alignment of the fork. Since several rear wheel spokes are definitely loose though, that is more likely the cause of my shimmy.
     
  7. BicyclingGuitar

    BicyclingGuitar New Member

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    Rear wheel spokes tightened, problem solved. The clue was that the shimmy problem was worse when there was weight on the rack over the rear wheel. Front fork alignment wasn't checked. My bike tracks straight and is very stable riding with no hands.
     
  8. BicyclingGuitar

    BicyclingGuitar New Member

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    Well, I *can't* afford it but I had new wheels built anyway! They are SO nice! I do notice some difference in how the bicycle handles as I ride with no hands playing guitar. It seems to take slightly more room to turn around than when I was riding with steel wheels, but since I had been riding this bike with the steel wheels since the early 1980s I probably just need to get used to the new feeling. It may end up being able to turn TIGHTER than before once I get used to it.

    Rainy season is here in Oregon though. When it's not raining and not too cold, I'll probably be able to ride for a couple more months still. Once winter truly arrives I won't be riding at all though. I *only* ride while playing guitar, and cold and wet isn't good for the guitar or for my fingers!

    [​IMG]
     
  9. steve

    steve Administrator
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    Thanks for the update, I have a similar problem that could be caused by my cheapo mavic wheels. For some reason I never thought of testing another set of wheels, i was sure my forks or frame was the cause.

    regards
     
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