Cassette Replacement Question- Mtbr.com
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  1. #1
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    Cassette Replacement Question

    I'm in the process of rebuilding my commuter road bike. I've basically stripped the entire thing down to the frame, which is being powder coated this week. I need to replace my cassette which is currently a 12-25 Shimano 9 speed. I would like a bit lower gearing for hill climbing, and my question is: How much bigger can I go with my cassette? Would something like an 11-32 9 Speed be too large?

    Thanks for any feedback.

  2. #2
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    it is very unlikely a bigger granny sprocket on the rear cassette will interfere with the frame tire or derailleurs...

    Need to do a tooth count to establish the required length of the derailleur arm...

  3. #3
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    What derailleur are you using now? That will determine if a new derailleur is required.
    '15 Niner Jet 9 Carbon
    '19 Karate Monkey
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    Raleigh Willard 3, Furley & Militis 3 (SS)
    Nashbar Carbon Road

  4. #4
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    Shimano 9 speed road and mountain are compatible with each other, so find an older Deore or XT and go as big as you want.

  5. #5
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    Yeah, that's a derailleur question, not a cassette question. Cassette granny ring can be as big as your derailleur can handle.
    You have no excuse for driving to work
    (unless you don't have studded tires)
    (no excuse for that either)

  6. #6
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    Any idea what derailure you have, and how many chainrings do you use up front?

    Agree with above. also want to check chain length. If you're getting a new chain (which you should do if you're getting a new cassette), not a problem. If you're breaking all the rules and keeping your old chain, it might not be long enough because of the increased cog size.

    In summary, get a new chain too.
    "a hundred travel books isn't worth one real trip"

  7. #7
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    I don't have the derailleur in front of me right now, but off the top of my head its a Shimano Tiagra 9 Speed. Also note this is a road bike (old Giant OCR 2) and not a MTB.

    I will also be replacing the chain along with lots of other various parts that are all used up.

  8. #8
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    Quote Originally Posted by p08757 View Post
    I don't have the derailleur in front of me right now, but off the top of my head its a Shimano Tiagra 9 Speed. Also note this is a road bike (old Giant OCR 2) and not a MTB.
    Looks like you might need a new derailleur then. Have to verify the model number, but it looks like 27T is the max cog size. Worst case, get a deore 9-speed mountain derailure and go up to 32 easily. As mentioned, same road shifter will work with a rear mountain derailure, so it's an easy swap.

    http://www.shimano.com/media/techdoc...9830607047.pdf
    "a hundred travel books isn't worth one real trip"

  9. #9
    CB of the East
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    You are interested in the cage length of the derailleur which will determine it's "capacity". If it is a short cage road derailleur then it might not work but if it is medium or long it should. Here is some info on determining the capacity.
    Understanding Rear Bike Derailleurs - Performance Bike Learning Center.

    Worst case you can try it. Break the chain so it fits over the large/large combination through the derailleur with just a little extra and then shift to small/small and make sure there is no slack (droop) in the chain. Even if there is you can avoid that gear. Or you can spend about $35 on Jenson and get a new one.

  10. #10
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    Quote Originally Posted by p08757 View Post
    (old Giant OCR 2)
    Memories...Cassette Replacement Question-picture1.jpg
    You have no excuse for driving to work
    (unless you don't have studded tires)
    (no excuse for that either)

  11. #11
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    Quote Originally Posted by CommuterBoy View Post
    Memories...Click image for larger version. 

Name:	Picture1.jpg 
Views:	22 
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ID:	1034452
    That looks like a 2001. Mine is a 2003:


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