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  1. #1
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    An Unstable Ride

    Hey gang,

    My first post!

    So I know my way around a bike. I've raced, I've worked in bike shops etc. However, recently I have been experiencing a very unstable ride on my new Supersix. Basically, when i go at speed, or up or down a hill the bike turns into a bucking bronco. It hops vertically, and will also shake laterally.

    What would cause something like this? My fit to be bike? Am I too heavy for my wheels? (I stopped riding for a year and gained some weight. I'm 180 now)

    I'd really appreciate any advice! If you need to know more I'm glad to update the post.

  2. #2
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    Are your wheels true? No broken spokes?

    P.S.: 180lbs? Don't be silly, any wheel can take that no problem.

  3. #3
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    Could be many things like a loose headset, loose wheel bearings, loose skewer, a crack in the frame or fork, or a fork that is not straight (described at Fork Symmetry | Calfee Design)

  4. #4
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    I would first start with a visual inspection, tires out of round, wheels out of true, the easy stuff. Then take it for a ride again. If it still does what you said do you ahve a extra set of wheels you can borrow to just swap out and try again.
    If it happens again you now know it isnt the wheels in any way shaper or form. But it it stops you know the problem area. I was thinking bad tires.

    Let us know. Bill

  5. #5
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    Quote Originally Posted by CruachanSean View Post
    Hey gang,

    My first post!

    So I know my way around a bike. I've raced, I've worked in bike shops etc. However, recently I have been experiencing a very unstable ride on my new Supersix. Basically, when i go at speed, or up or down a hill the bike turns into a bucking bronco. It hops vertically, and will also shake laterally.

    What would cause something like this? My fit to be bike? Am I too heavy for my wheels? (I stopped riding for a year and gained some weight. I'm 180 now)

    I'd really appreciate any advice! If you need to know more I'm glad to update the post.
    The bike does this on uphills, too? That is odd (I'm assuming that your uphills aren't "at speed?")

  6. #6
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    Quote Originally Posted by crossracer View Post
    I would first start with a visual inspection, tires out of round, wheels out of true, the easy stuff. Then take it for a ride again. If it still does what you said do you ahve a extra set of wheels you can borrow to just swap out and try again.
    If it happens again you now know it isnt the wheels in any way shaper or form. But it it stops you know the problem area. I was thinking bad tires.

    Let us know. Bill
    ^^ This

    Loose headset would have been my first guess but I assume you've checked this. Check everything for unwanted play and then swap out the wheels. I'm thinking bad tires (or even tube?) too. If it were a car, I'd say the wheels were out of balance but I've never heard of this being noticeable on a bike. Too many spokie dokes on one side of your wheel?

  7. #7
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    Quote Originally Posted by carveitup View Post
    If it were a car, I'd say the wheels were out of balance but I've never heard of this being noticeable on a bike.
    I might have, or just wheels not strong enough. My last set of wheels would get the wobbles real bad on a fast descent. It could have been that they were too flexy 16/20 CX ray spokes for my 190lbs.

    In addition to all the above advice, maybe lowering your tire pressure a little bit and keep pedaling while going down will help add stability.
    My carbon footprint has cleats

  8. #8
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    Quote Originally Posted by carveitup View Post
    If it were a car, I'd say the wheels were out of balance but I've never heard of this being noticeable on a bike.
    In order for a bounce to develop in an out-of-balance bicycle wheel, the tire would have to compress significantly. Given the typical static load on the tire (90-110 lb. or 40-55 kg in the case of the OP) it is unimaginable that some amount of wheel imbalance could impart a force on the tire within an order of magnitude of the existing load and therefore no way it could significantly compress the tire and cause a bouncing movement. Not possible.

  9. #9
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    Doubtful the wheels aren't strong enough.

    If the wheels/bike are hopping vertically, there's a good chance that the wheels (or perhaps the tires) are out of round. Pull the tires and put it in a truing stand and it should be pretty obvious if that's the problem. I'm also assuming this happens on more than one hill. Otherwise, there might be small irregularities in the pavement that match the harmonic frequency of your bike at the speed you're going.
    "Five and Dime, all the time!"

  10. #10
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    Next time when you're going downhill at about the speed where this happens place/lean your knee against the top tube. My bet is that will stop it. I have a couple of bikes that do that & after a thorough investigation I just resort to the knee. You don't have to exert a lot of pressure-lust a little.
    Before you criticize someone walk a mile in their shoes. That way when you criticize them you'll be a mile away & you'll have their shoes.

  11. #11
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    I have a Specialized Armadillo tire that causes my bike to 'hop' at speed. It looks fine but the problem goes away when I change the tire. Try new tires after checking the other things listed above.
    Embrace the fact that everyone on these forums has their own unique desires, needs, experiences and environment so what works for you may not work for others.

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