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I bought a second hand bike and there was some noise and jerkiness coming from the driveline. I checked the chain and it was worn off, and I have changed it. Noise is reduced but still every now and then (let's say every 10 times i pedal) the crank behaves jerky.

Could the crankset be the issue ? I have seen the following marks in the sprockets. enter image description here

The crankset is "175 FC-TY301". A quick search also lead me to a model called FC-TY501. Is 501 a better model than 301 ?

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    You clearly have another chainring there. Test by riding in that ring and see if the problem changes ?
    – Criggie
    Aug 5 at 9:31
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    Yes, i have 3 chainrings, as per the model 175 FC-TY301. In the photo, only the 3rd ring is shown but other rings have also very similar marks. And riding in the other rings(gears) also produce the same sound.
    – Erman
    Aug 5 at 15:43
  • At first glance, those chainrings do not look very worn out, albeit being a bit muddy. Clean them with an old tooth brush and soapy water, and take another picture, if possible, from more than one angle. Some chainrings have "weird" marks or tooth profiles in certain spots that may look like damage, but are actually there to facilitate gear shifts. A mis-adjusted deraileur may cause some noise and jerkines when the chain meets those spots in the chain ring.
    – Jahaziel
    Aug 5 at 20:02

2 Answers 2

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It sounds like you replaced a very worn chain.

I would keep the cranks, but replace the chainrings (i.e. front sprockets). You might need a new cassette (collection of rear sprockets) as well.

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  • Unfortunately, chainrings have riveted connection in this design, therefore i can not replace the chainrings, i have to change the whole assembly.
    – Erman
    Aug 5 at 22:52
  • @Erman: It might be possible to drill out the rivets and replace them with bolts (and bolted chainrings).
    – Michael
    Aug 9 at 10:39
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Sorry to hear!

I have fixed a, 'clicky creak' like this by re-greasing the BB (Bottom Bracket) bearing and cleaning the area out. It is not uncommon that a BB starts to make noises. The give-aways are that it has jerkyness (bearings loose) and it doesn't happen at the same point of each crank rotation. Also that it happens on all 3 rings. The BB bearing should be rust & particle free, it should move freely without any okay. It should be well greased. Failing this, get a replacement BB bearing, you should be able to find the details on the existing one, make note of part number/width and diameter.

If it's not BB, it could be the peddle/s. A bent chainring. The previous owner upgraded the cassette to have more than 8 speeds, of which the front rings aren't designed for 9+ speed chains. It could be the tyre on the frame, the brakes and so on. It depends what you have done to isolate the noise. Sometimes we can be sure it's coming from one place, but then it turns out the sound/s is coming from somewhere totally different!

Re: 301/501.. I see little difference, both are 170mm crank arm lenth, fit square taper and are designed upto 8 speed. So both will work. The 501 I believe is a small amount more expensive and has a 4mm larger arm spacing. Anyway, you're still talking about bottom-end Shimano Tourney components so don't expect any notable riding difference.

Cheers, Manx Tatty.

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  • Hi Joe (or Manx Tatty) Thank you for your detailed answer. Tomorrow i will remove the existing crankset, so i can hopefully reach the BB and learn more about it. Meanwhile, since i have just changed the chain, i do not believe the bent chainring has anything to do with this. Also, on a bike stand, when i disengage the chain, no matter how strong i hit the pedals, it doesnt jerk or do the "clicky creak". Therefore, i do not believe pedals have something to do with it either. Thanks for the tip about 301/501. Is there any improvement i can make ? what would you suggest ? (up to 75€ or so)
    – Erman
    Aug 8 at 19:46

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