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Cassette size for medium derailleur

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  • March 9, 2020 at 5:33 pm #30537
    rob39

    Running Shimano RD 5800 medium rear derailleur with a 11-32 cassette. Will the derailleur take a 11-34? Would I get away with out changing chain?

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  • March 13, 2020 at 12:22 pm #956609
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    ktache

    As I said in my little tale,

    As I said in my little tale, it wasn’t for me.  Cranks would not turn, forwards or backwards.  Total jam and lock up.  And it really wasn’t easy to get the back wheel out.  Cross-chaining is bad, but this was awful.

    Even with a new correctly lengthened chain, when travelling through this particular car park, I would always check that I had gone into the middle on the front.  It was that bad and scary.

    Even coming down a big downhill, it was not a bad thing to slow down a bit, train station car park at the end of evening rush hour is a risky place for a cyclist, even with big lights and lots of Hi Viz.  

    https://road.cc/wp-content/uploads/roadcc/ashvale car park.PNG

    March 13, 2020 at 12:01 pm #956607
    0
    fukawitribe

    Big-big will be fine – well,

    Big-big will be fine – well, as fine as big-big on the 32 was.

    March 12, 2020 at 11:22 pm #956605
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    TheBillder

    I went from 28 to 34 on
    I went from 28 to 34 on a medium cage Tiagra with no change of chain (it was almost new). It’s perhaps slightly shorter than ideal but still works well, and staying away from big-big helps.

    March 10, 2020 at 7:14 pm #956603
    0
    ktache

    I ran a seven speed system on

    I ran a seven speed system on an eight speed casette, mainly because the XT STI levers operated my cantilevers and you could not get quality seven speed casettes, or at least eight speed were easier, but I used the smaller seven cogs, my commute changed and because of one particular off road hill (Crown Prince Hill in Ash Ranges) I sometimes needed better gearing, so I shifted the derilleur to use the bigger seven cogs.  I was still using the same chain, with the length optimised for the earlier set up.  It all still worked well, until I desended a big hill on the big ring, got to a car park, dropped a couple of gears, and then came to a stop at  a road junction, went down a few more.  Terrible, I know, but I went big big and the whole drivetrain jammed, it was not easy getting the chain onto a gear so that it would work, frustrating, had to whack the rear wheel out.

    If you keep the chain, DO NOT go big big.

    March 10, 2020 at 6:42 pm #956601
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    Skimpy1

    And assuming that there is

    And assuming that there is only limited wear on your current chain.

    I would always work on the assumption that a new chain is required when changing cassette.

    March 10, 2020 at 4:31 pm #956599
    0
    fukawitribe

    Yes and almost certainly yes,

    Yes and almost certainly yes, unless maybe your existing chain is staggeringly tight to the point of almost not working already.

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