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Need Some Help, Please
I recently took my bike in because of a knocking sound I have been having from time to time only while pedaling. It is not always constant and can come and go without anything (that I have noticed) triggering it.

I took it into my local bike shop and I ended up spending $100 for everything; got a new chain, had everything cleaned, etc. None of it fixed the problem so I brought it back in to see what they thought. The noise cannot be reproduced unless you're actually on the bike and pedaling. They wanted another $50 for something they said "may or may not" fix the problem so I decided to pass for now as I don't want to keep throwing money at an issue without knowing it actually will get fixed.

I attached a GoPro to the bike, seeing if I could notice anything myself (though I am no expert), but mainly to record the noise so I could get some opinions about what it might be.

At about the 1:20 mark in the video the noise starts and gets progressively worse. I stop pedaling at points to show that it only happens when pedaling. I also shift to several different gears to show that it is not associated with any particular gear. The noise persists and yet by the end of the short clip is gone. When riding long distances it comes and goes and comes again.

Any help would be greatly appreciated as this is frustrating and annoying.

Link to vid. https://www.youtube.com/watch?v=GQn--zGQ5uQ&;
A competent shop should not be replacing parts and cleaning until they know the problem - cart before the horse. What you really need is a good mechanic and diagnostician on the bike, but you might check to make sure the BB is tight in the shell, as that can cause a knocking/clunking sound/feel. Also possible is a freewheel/freehub problem. Chain is unlikely.
do you have a plastic spoke guard behind your rear cluster? Is it loose or broken, remove it. retest. you can try swapping rear wheels and test again to help isolate the rear or not, then focus on the front chainwheel/BB area.
I have a rear wheel in my true stand right now with a loose spoke guard and can almost duplicate your sound when I spin hard. the guard will break loose make the noise then hang up and be quiet, then I can pop it with my hand to simulate a bump in the road and it will start to make noise again until it hangs up and stops again
There are two kinds of people in the world, "Those who help themselves to people, and those who help people!"
I will start with the rear spoke guard, it is loose, or at least swivels. I will go from there and see what happens. Thanks a lot for all the advice.
OK, some thoughts -
The noise is the same rhythm no matter what gear you are in, but rather in time with bike speed.
That means it can't be anything related to the BB/cranks.
It also *cannot* be the chain, which travels around the bike at different rates in different gears, and in any case would not have a rhythm that fast and regular if there were tight links, for example.
Could very well be a spoke protector. The other guess would still be freehub.
If the head mechanic did not look at the bike you need that to happen, and it absolutely needs to be test ridden by a mechanic. If the head mechanic did look at it you need another shop.
So far so good after messing around with the spoke guard on the rear tire. I have gone out for several rides since and haven't had any trouble with the noise. I appreciate all the help you guys offered. Saved me money and headaches. I will post an update if it starts up again and fiddling with the spoke guard doesn't fix it next time. Keeping my fingers crossed. Smile
I use them til they crack, warp or cause trouble or even turn yellow if they are plastic. then just remove them. not really needed. unless a vintage resto with a nice metal one. Hope that does it for you, if it does I take paypal donations too! Smile
There are two kinds of people in the world, "Those who help themselves to people, and those who help people!"
I think it is better for you to take the bike into the service center and they will remove the knocking sound of your bike. There are number of website in online regarding the services of the bikes. So you can choose any of them.
I visited your Youtube site, I have a similar noisy knock. I deduced it was either the bottom bracket or rear wheel bearings but I felt since I have a sealed bottom bracket assembly that is less than a year old, it was unlikely to be the bottom bracket assembly. I removed, cleaned, measured the rear wheel bearings. The bearing balls were supposed to be .250" in diameter but were .238"......badly worn. I think that the loss of .012" on each of the 9 balls creates a gap of .108" (slightly less than 1/8") which could cause the balls to shift, thus "knocking" when under the load of pedaling while accelerating. Having no bearing balls in stock, I tested my theory by greasing the old balls well. The noise totally disappeared for the first mile, then returned. I ordered some quality bearing balls. Maybe you just need new rear wheel bearing balls.

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