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I have a Charge Mixer bike with, I believe, a Shimano Alfine Inter-8 internal hub gear system. Recently the chain started to creak so I decided to change it. I bought a KMC X9 chain as Shimano appear to recommend a 9 speed chain. This chain does not fit around the chain ring so I assume that the old stretched chain has worn/damaged the chain ring, so I have decided to replace the chain ring and sprocket. How do I find out which sprocket and chain ring I should buy? Is counting the teeth enough?

I have always found the gearing slightly too low, ie, I often use the highest (hardest) gear and infrequently use the lowest (easiest). Is this an opportunity to fix that? eg, can I get a bigger chain ring and/or smaller sprocket?

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    Creaking could be a lot of different things. What else did you try before replacing the chain? How did you determine the chain to be the source of the sound?
    – SamA
    Commented Sep 15, 2022 at 10:24

1 Answer 1

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There is a dealer's manual for the Alfine Inter-8 on the Shimano website with the following table which says that the chain ring model is FC-S501, sprocket CS-S500, with possible teeth ratios of 45:20, 42:20 or 39:18.

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I have not found the official advice on chain width, but multiple sources online say that Shimano recommend 9 speed chains.

Update: I have now switched my 39:18 chainring and sprocket for 45:20 replacements, models FC-S501 and CS-S500 and put the X9 chain on and everything seems good. I'm not sure I can detect the difference in the ratio, though that's probably better than it being too different. I couldn't believe how easy it was to change these parts on a 15 year old bike.

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    I removed my answer. Sorry for the incorrect information. Shimano recommends a 9 speed HG series chain on the product page: bike.shimano.com/en-EU/product/component/alfine-s7000s700/…
    – SamA
    Commented Sep 15, 2022 at 13:24
  • Why don't you get the 18t sprocket for your hub? Usually there is enough adjustment in the chain length to try this and the sprockets are cheap. You can also use Sturmey Archer sprockets if you want more choice, if your hub uses the "three lobe" attachment. Going to 18t will move all your gears up by a small but noticeable amount.
    – Noise
    Commented Sep 21, 2022 at 18:50
  • Your new ratios are nearly identical to the old ones! kstoerz.com/gearcalc/compare/…
    – Noise
    Commented Sep 21, 2022 at 18:54
  • The new ratio has 3.8% more development. If OP had to pedal at 100rpm to reach a given speed in a certain gear, they now only have to pedal at 96rpm. Noticeable but not world changing. I’m surprised Shimano doesn’t give more freedom in sprocket/chainring selection. If you have 175mm length crankarms you could go to 170mm for another 2.9% ;)
    – Michael
    Commented Sep 22, 2022 at 6:58

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