Sora 9 speed gearing/chain length?

tonysj
tonysj Posts: 391
in Workshop
Hi All,
I have a BTwin Triban 520 triple front ( 50/39/30t ) with a 32t - 11t rear cassette ( original has a 25t - 11t cassette) and a GS/Medium Rear derailleur. The chain needs replacing and I've got one ready to change over. It currently has 106 links on the bike but wondered if its worth leaving a couple more links in the chain as occasionally I cross chain by error from large front to large rear and it locks out resulting in a lot of fiddling and messy hands to release it.
Is there an online tool that will give a hint as if its doable?
Regards.
Tony.

Comments

  • Munsford0
    Munsford0 Posts: 678
    edited March 2021
    Lucky you've not ripped the rear mech off doing that!

    I have a 105 10 speed triple with the same chainrings as you and an 11-32 cassette so it's definitely doable.

    Shimano tech docs says this:

    For front triple (when largest sprocket is 32T or larger)

    With the chain put on both the largest
    sprocket and the largest chainring, add
    2 links to the "minimum number of links
    that can be connected".

    So thread the new chain round the big / big combo but not through the rear mech, mark the point where you could in theory join the chain. Take it off and cut it to be 2 links longer than this. Then install taking care to thread it correctly through the rear mech
  • tonysj
    tonysj Posts: 391
    Munsford0 said:

    Lucky you've not ripped the rear mech off doing that!

    I have a 105 10 speed triple with the same chainrings as you and an 11-32 cassette so it's definitely doable.

    Shimano tech docs says this:

    For front triple (when largest sprocket is 32T or larger)

    With the chain put on both the largest
    sprocket and the largest chainring, add
    2 links to the "minimum number of links
    that can be connected".

    So thread the new chain round the big / big combo but not through the rear mech, mark the point where you could in theory join the chain. Take it off and cut it to be 2 links longer than this. Then install taking care to thread it correctly through the rear mech

    Thanks Munsford0,
    I decided to increase the chain length by 2 links over the original as I could always take them out if it didn't work or caused shifting/clearance issues.
    Seems OK and works Large to Large/cross chaining just in case I have a mishap.
    Thanks.
    T.

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