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I'm trying to find a 24/34/42 175mm square tapered crankset for a 7 speed mtb rebuild but can only find a 24/34/44 crankset. Will the 2 extra teeth on the large chainring be a problem for me? would I have to change any other components ( like my chain, or rear wheel cassette so everything works perfectly?

Note* the rear wheel cassette I'll be using is a stock 7 speed 13-28 cassette.

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  • Are you fitting a new chain and freewheel as well ?
    – Criggie ♦
    Commented May 17, 2023 at 20:33
  • @Criggie Yes. im going to try and get the same as I had before 13-28t 7 speed cassette and definitely a brand new chain.
    – Matt
    Commented May 17, 2023 at 23:58
  • good luck! 13-28 freewheel is uncommon, the majority are 14-28. In that case your hardest gear will get slightly easier, so a slightly larger chainring will somewhat balance that.
    – Criggie ♦
    Commented May 18, 2023 at 1:39

1 Answer 1

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The issue with larger chainrings is usually frame clearance, but with a triple and only 2T difference, very unlikely that it will be an issue.

For the rest,

  • You may need a slightly longer chain (1 link).
  • The rear derailleur would need an extra 2T capacity, but that would depend on the current derailleur: considering that the current one is "within specs", it may have enough capacity, and if not, 2T is usually not an issue if go beyond the rated capacity - the main risk is to have too much slack when being on small rear sprockets and and small chainring.
  • The front derailleur may not have enough capacity, but that's very unlikely. The radius difference between a 44T chainring and a 42T chainring is about 3mm. Front derailleurs in this segment are usually not optimized for one size, so it should be OK (for example the current Tourney TX goes from 42T to 48T), but it may be useful to check that too. Again, there's a tolerance if you are at the theoretical limit, so best to simply try if you already have the parts.
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    Thanks for your answer Renaud! The only specs I have for this bike that may be relevant is this: Front Derailleur: Shimano Altus Rear Derailleur: Shimano Acera Crankset: SR Suntour PFF 8 speed XR180, 24/34/42 teeth Rear Cogs: 7-speed, 13 - 28 teeth Chain: 1/2 x 3/32"
    – Matt
    Commented May 17, 2023 at 19:55
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    Altus and Acera are product ranges, used for many years, so that won't be sufficient to check. Usually, Shimano writes the model on the components, the format should be FD-Mxxx for the front derailleur and RD-Mxxx for the rear one.
    – Rеnаud
    Commented May 17, 2023 at 20:08
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    @Matt An RD-MD330 has a 39-tooth capacity. Increasing the large front chaining by 2t will require a 35t capacity - your original 33t plus the two added, well within the capabilities of an RD-M330. Changing the front chainring size won't have much if any effect (outside of the change in needed capacity) on the RD (within reason, but you'd run into other problems first with FD reach/position or hitting the frame - or ground.).
    – Andrew Henle
    Commented May 17, 2023 at 22:29
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    @AndrewHenle Thanks for your answer. It got me searching and I just found a manual online for the Shimano RD-M330. yep 39t cap. awesome. As far as FD goes, I'm expecting I will have to adjust the position to accommodate for the slightly larger 44t chain ring.
    – Matt
    Commented May 18, 2023 at 0:17

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