DuraAce 9150 Cassette Size
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  1. #1
    RoadBikeReview Member
    Join Date
    Jun 2004

    DuraAce 9150 Cassette Size

    I am about to get a bike with the new D/A Di2 (non-disc) groupo. It comes with 36/52 front chain rings and an 11/28 in the back. The Shimano website says the new D/A can take up to a 30 tooth cassette. I would like to put an 11/32 on the back. Has anyone tried this on the new D/A Di2?

    I'd also like to put a 34 on the front in place of the 36, and run a 34/52 in front. Has anyone tried this either? I know you can't do it on the mechanical group, but I've heard you can with the electric.


  2. #2
    RoadBikeReview Member
    Reputation: spdntrxi's Avatar
    Join Date
    Jul 2013
    likely the RD can handle it... hell even the 9070 could but it's also frame dependent .. For example 32 clears on my wife Madone but not on my parlee. B screw fully done and cannot adjust anymore. This is due to the difference in hangers. I can ran SRAM 30T no problem on my parlee.

    As for the 52/34 .. it works but not as crisp, but I've only tried with electric since that's what I have.. but 50/34 and 52/36 work better then 52/34.

  3. #3
    'brifter' is a lame word.
    Reputation: cxwrench's Avatar
    Join Date
    Nov 2004
    A rear derailleur does a couple of things, one of which you don't seem to understand. Obviously the derailleur shifts the chain over the cogs. It also wraps a given amount of chain so that you can have a long enough chain on the bike to work in both big/big and small/small. If you surpass the chain wrap capacity of the rear derailleur by using a larger big cog than specified and/or increasing the max difference between the chainrings you risk one of 2 things happening. If you use the normal chain sizing method you can pull the rear derailleur too far forward when using big/big and damage it or possibly rip it off the bike. Or, if you size the chain extra long so that you have enough length to use big/big you'll have a bunch of chain slack when in the small ring and small cogs.

    Front derailleur spec for FD-9150 is 16 teeth just like all Shimano road double derailleurs. Of course you can screw w/ the spec and run more than 16 but it won't shift as well and you'll end up w/ rub that you won't normally get if you stick to their spec. Shimano doesn't engineer a certain spec for no reason, they say 16 teeth max because that's what works best. You can trust me when I say their legions of engineer geeks know how to design things like derailleurs and when they say it works best w/ 16 teeth max difference between big and small rings it's the truth.

    When doing what you're trying to do you have to remember it's not just whether or not you can get the upper pulley to clear the large cog, it's important to remember that other things are affected as well. You're looking at a race group, not a recreational group. If you need a 34/32 to climb hills, buy Ultegra.
    I work for some bike racers
    I've got some bikes, some guns,
    and a bunch of skateboards

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