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I really need your suggestions. The situation is bellow: I have bought brand new one "Specialized Rockhopper Sport 29" 2017 satin navy-hyper" in a official dealer of Specialized.

When i arrived at home, just for interest rotated bicycle and checked the spinning... during the spinning i noticed that pedal and cassette was shaking - confused, went back to shop and asked them for change but they told me that this is totally normal and there is no bicycle without this.

Maybe it is a hub problem and thats why it shakes.

Still wondering, need your advice, should i take care about it or it is normal?

Here is the video:

Youtube:

Vimeo: https://vimeo.com/236250012

Please consider the fact, even when i touch to cassette it is obvious that it shaking really.

Thanks a lot. Look forward to hearing from you people.

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    Looks fine to me there is bound to be a tiny bit of movement during freewheeling upside down. You will not notice it while riding – Nate W Oct 10 '17 at 21:54
  • You say cassette, but don't you mean chainrings? (The cassette is the rear gears; the chainrings are attached to the cranks.) – David Richerby Oct 11 '17 at 0:00
  • NateWengert Yes, during the riding i do not feel anything, but i mean during the free hub spinning it is obvious. DavidRicherby nope, chainrings is fine, i mean literally gear cassette, it moves up and down during the spinning : ) – George Oct 11 '17 at 6:26
  • It would be helpful if the video showed the problem. What I see is that focus is on chainrings and cassette, when it is visible, is at most rotating a bit back and forth. – ojs Oct 11 '17 at 10:01
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    Rule #49 Keep the rubber side down. from velominati.com/the-rules ;-) – Carel Oct 11 '17 at 12:35
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I can't see anything wrong at all.

The any vibration you may feel when the rear wheels is spinning but the cranks and chain and cassette are not moving is due to the clicking of the pawls in the free-hub.

I think if you hold a pedal and spin the cranks so the rear wheel turns you will not detect any vibration or 'shaking', as the free-hub will engage.

I think if you ride the bike you will find it functions normally.

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  • Even holding the pedal i can detect the vibration. During the riding there is no problem at all, just wondering about this fact - cassette is literally vibrating up and down thats all : ) So if it should be like this with a brand new one - i can do nothing... Can this problem affect to another parts? Thank you – George Oct 11 '17 at 6:31
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Another possibility is that the "shaking" you are seeing is due to the (expected!) wheel unbalance.

No bike wheels are truly balanced the way a car wheel would be. Weight doesn't matter for car wheels, so those wheels are balanced by adding weights to the rim. On bikes, the forces are lower and saving weight is more important, so we don't bother. This means that the tire valve and reflector, however light, are enough to noticeably unbalance the wheel. When you allow the wheel to spin freely off the ground, this imbalance causes the wheel, drive train, and even possibly the whole bike to shimmy a bit.

But don't worry! This has absolutely no effect once you actually put it on the ground and start riding it.

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  • Yeap, during the normal riding it is not noticeable at all, but it seems something like the rim is not balanced or something like this... just wondering - this vibration is up and down for cassette as well not only for pedal... – George Oct 11 '17 at 6:35

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