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  1. #1
    jta
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    Determining chain length on a chain that's already installed

    Sorry, I'm sure this topic's been covered before:

    I just took delivery of a new bike with an Ultegra 8000 drive train. It came with 52/36 and 11/32 gearing and I immediately swapped it out for 50/34 and 11/28.

    Should I shorten the chain?

    I am familiar with Shimano's dealer manual and their method of determining chain length for cassettes that have cogs with 28T or more, but it doesn't seem to help with a pre-installed chain.

  2. #2
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    Parks Tool has a good video section that covers this(chain sizing), among others, also will you by chance be putting the 11/32 back on at any time.

  3. #3
    Not a rocket surgeon.
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    Shift small, small. Is the chain slack? If so, its too long.
    Go to the big ring, slowly shift down the cassette from the small cog. Watch the rear derailuer, does it go tight? The cage should not be rotated much forward of vertical. If it can get into all ranges, its good.

  4. #4
    jta
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    Quote Originally Posted by Ventura Roubaix View Post
    Parks Tool has a good video section that covers this(chain sizing), among others, also will you by chance be putting the 11/32 back on at any time.
    thanks, good advice - I actually referred to that video awhile back and forgot about it.

    No chance the 11/32 is going back on. My other bike is set up with a 12/25 and I rarely use the 25T cog.

  5. #5
    jta
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    Quote Originally Posted by tihsepa View Post
    Shift small, small. Is the chain slack? If so, its too long.
    Go to the big ring, slowly shift down the cassette from the small cog. Watch the rear derailuer, does it go tight? The cage should not be rotated much forward of vertical. If it can get into all ranges, its good.
    Thanks, between the PT video and this, I think I'll be able to figure it out. The small/small method is what I'm familiar with, but Shimano has different instructions for 28T and above.

  6. #6
    jta
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    Okay, tried the small/small technique then switched to the big ring and went through the range. The chain seems to be okay as is for now.

    A bit surprised, but then I only lost 2 teeth in the small/small combination and in the big/big, the chain is pretty taut, so it must have been nice and snug with the bigger rings.

  7. #7
    jta
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    Update: Went ahead and took two inks out. I have an extra 12-25 cassette sitting around. I should be able to go back and forth from 11-28 to 12-25with out worrying about chain length now.

    BTW, shifting on Shimano's new groupsets (DA9100 and Ultegra 8000) seems to be an improvement over previous - the short throw on the front lever makes shifting onto the big ring effortless.

    Thanks for the advice everyone.

  8. #8
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    Quote Originally Posted by jta View Post
    Update: Went ahead and took two inks out.
    Why? If the chain wasn't hanging slack in the small-small combination, there was absolutely no reason to remove links. Things do not work better with a shorter chain.

  9. #9
    jta
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    Quote Originally Posted by Kerry Irons View Post
    Why? If the chain wasn't hanging slack in the small-small combination, there was absolutely no reason to remove links. Things do not work better with a shorter chain.
    I am admittedly not the expert here - just trying to follow the guidance of Park Tools and others that know more than me.

    As I mentioned I wanted to be able to swap out to a smaller cassette in the future and not worry about it. Figured this was a way to cover both options.

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