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Old 03-02-14, 10:23 AM   #1
MikeyUK
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Rear Wheel Unbalanced

Hi guys.

I got my first bike from my local bike shop a few weeks ago and have recently noticed that the rear wheel feels unbalanced. I can't feel anything whilst riding it, but if i lift the bike up by the seat and spin the wheel, the bike pulls my arm up and down in my hand (hope you can understand what I mean here). I have also had the bike in a friends bike stand, and can see the rear cassette and the chain moving up and down slightly as the rear wheel spins.

I would like to get your opinion before taking it back to the shop to have checked out.

Thanks!
Mike.
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Old 03-02-14, 10:54 AM   #2
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Quote:
Originally Posted by MikeyUK View Post
I can't feel anything whilst riding it,
Other than riding it, what else do you want from your bike?
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Old 03-02-14, 11:57 AM   #3
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Sounds like gyroscopic forces...

As for the cassette moving, they don't tend to run out perfectly true. They are on a slip-fit, loose tolerance connection, not a precision connection by any means.

If you think its really bad, take it in by all means to make sure (I can't see it so I don't want to say its fine...) But if you can't feel it, I'm guessing its no big deal
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Old 03-02-14, 11:57 AM   #4
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rims have seams, they are a rolled up extrusion.. there is a seam opposite from the hole for the valve stem.
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Old 03-02-14, 11:57 AM   #5
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Quote:
Originally Posted by MikeyUK View Post
I can't feel anything whilst riding it,
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Originally Posted by Retro Grouch View Post
Other than riding it, what else do you want from your bike?
Agreed. Sounds like the wheel is just fine. The shop will probably just laugh at you.
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Old 03-02-14, 01:58 PM   #6
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Originally Posted by MikeyUK View Post
......but if i lift the bike up by the seat and spin the wheel, the bike pulls my arm up and down in my hand......
Most of that is probably tire, not wheel.
Use a zip tie or similar with the end pointing close to the rim as a pointer.
Spin the wheel and observe the rim for hop/wobble etc.
Look at the tire to make sure it's seated "concentrically" on the rim.
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Old 03-02-14, 02:20 PM   #7
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Yes, your wheel is unbalanced. And yes it's 100% perfectly normal.

The tire has a valve of a certain weight, and there's no counter-balance opposite. So the wheel is unbalanced. Bicycle wheels aren't balanced as car wheels are partly because it isn't necessary for the speeds they spin, and partly because balancing implies adding weight, while the overall goal is reducing weight.

The only problem you have is that you're looking too closely and finding anomalies which make you worry. It's a bike, there are plenty of subtle little quirks, but none matter if it rides fine.
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Old 03-02-14, 05:26 PM   #8
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Originally Posted by FBinNY View Post
Yes, your wheel is unbalanced. And yes it's 100% perfectly normal.

The tire has a valve of a certain weight, and there's no counter-balance opposite. So the wheel is unbalanced. Bicycle wheels aren't balanced as car wheels are partly because it isn't necessary for the speeds they spin, and partly because balancing implies adding weight, while the overall goal is reducing weight.

The only problem you have is that you're looking too closely and finding anomalies which make you worry. It's a bike, there are plenty of subtle little quirks, but none matter if it rides fine.
This man knows where of he speaks. http://yarchive.net/bike/wheel_balancing.html
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Old 03-02-14, 06:09 PM   #9
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Also, if you have a reflector on that wheel, that will make the wheel do what you are describing.
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Old 03-02-14, 06:53 PM   #10
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Thanks for all of the answers guys. Maybe I am looking a bit too closely at it. I might mention it when I take it in for the 6 week service but will just enjoy it until then.

Thanks
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Old 03-03-14, 03:41 PM   #11
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You're just noticing something few pay attention to. I'd add that if you have reflectors on your wheel, it can exacerbate that visual perception. Generally, you have to spin the wheel pretty quickly for it to be noticeable.
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Old 03-03-14, 04:12 PM   #12
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Quote:
Originally Posted by FBinNY View Post
The tire has a valve of a certain weight, and there's no counter-balance opposite.
Not quite right. On most rims the joint is directly opposite the valve stem. With conventional low profile wheels the joint is more often than not heavier than the valve stem. Spinning a wheel and letting it stop will usually show which side is heaviest. Presently I have 4 sets of bicycle wheels in my garage. With two of the sets the valve stems are short and the heavy side is centered on the rim joints. On the deep section (57 mm) the 60 mm valve stem is centered on the heavy side. The 4th set, with short valve stems, seems to be perfectly balanced.

I agree that it's normal for a bicycle wheel to be out-of-balance but that does not normally cause any problems.
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Old 03-03-14, 04:49 PM   #13
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Not quite right. On most rims the joint is directly opposite the valve stem. ....
Yes, there are a number of factors which can make other areas heavier than the rim. OTOH, I made a decision to relieve a newbie of newbie concerns with a simple abbreviated explanation giving a typical example, rather than a long discourse which might confuse him even more.

Also given his newbie status, and a new bike, there's a good chance that he has a Shrader valve on a low profile welded rim, so the valve would be the heaviest part, unless there was a reflector.
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Old 03-03-14, 06:09 PM   #14
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If you want something worth paying attention to regarding your wheels try this:
With the front wheel off the ground move the stem on the front wheel to the three o'clock position and then let go. The wheel should rock back and forth several times until slowly coming to a stop. Pull the chain off the rear cogs (have your friend help if needed) and repeat. If the wheel comes to a stop after only a cycle of two your hub bearings may be adjusted too tightly, which is common as the assembler does not always fix the too-tight factory adjustment. If so don't wait til your 6 week check.
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Old 03-03-14, 06:41 PM   #15
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Originally Posted by cny-bikeman View Post
If you want something worth paying attention to regarding your wheels try this:
With the front wheel off the ground move the stem on the front wheel to the three o'clock position and then let go. The wheel should rock back and forth several times until slowly coming to a stop. Pull the chain off the rear cogs (have your friend help if needed) and repeat. If the wheel comes to a stop after only a cycle of two your hub bearings may be adjusted too tightly, which is common as the assembler does not always fix the too-tight factory adjustment. If so don't wait til your 6 week check.
Of course, if it doesn't rock back and forth much, it could be well balanced, or a newly greased hub may be fighting the grease's viscosity. IMO, this test is an unreliable indicator of nothing. Back when I was in retail, we had to waste tones of time explaining this away when people came in all concerned.
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Old 03-03-14, 06:50 PM   #16
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Well, in my defense I said the bearings may be too tight. I suggested it because of the high proportion fo lowere end bikes that I have I seen that were much too tight. I adjusted my advice above to make it more conservative. I think it's fairly safe to say that if it comes to a stop almost immediately there's likely a problem. I did not want to recommend the OP take the wheels off, as I did not want to open that can of worms on a newbie.
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There's no such thing as a routine repair.

Don't tell me what "should" be - either it is, it isn't, or do something about it.

If you think I'm being blunt take it as a compliment - if I thought you were too weak to handle the truth or a strong opinion I would not bother.

Please take the time to post clearly so we can answer quickly. All lowercase and multiple typos makes for a hard read. Thanks!
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