Replace Ultegra 12-25T with 105 12-27T ?

josehernandez
josehernandez Posts: 243
edited October 2012 in Workshop
Can I replace my Ultegra 12-25T cassette with a 105 12-27T without having to worry about new chains or extra links ?

Comments

  • john-e-big-guns
    john-e-big-guns Posts: 489
    edited September 2012
    New block= new chain...if the block is quite new and not much wear ya should be OK...but if is an old chain/block with wear ya will have problems
    No Pain; No Gain;

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  • smidsy
    smidsy Posts: 5,273
    Quite probably, certainly the rear mech will normally take it.

    Chain - depends how short yours already is, but normally not an issue as you should not be in 50/27 anyway :-)
    Yellow is the new Black.
  • drlodge
    drlodge Posts: 4,826
    smidsy wrote:
    Quite probably, certainly the rear mech will normally take it.

    Chain - depends how short yours already is, but normally not an issue as you should not be in 50/27 anyway :-)

    +1, it SHOULD be straight swap.
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  • greentea
    greentea Posts: 180
    I recently replaced a 11-28 cog on an Ultegra rear with a Tiagra 12-30 cog and the chain didnt need replacing or adjusting at all. The rear derailleur was an Ultegra s/s.

    You should be fine. Try it first, then if its really bad change the chain afterwards, but im guessing you wont need too.

    The only thing you might need to do is screw in the B-screw a little bit, on the rear derailleur, to give you a bit more clearance between the small cog and the largest gear (27) but again, might not even be needed.
  • josehernandez
    josehernandez Posts: 243
    What adjustments would be required if I change from 12 - 25 to a 11- 28T ?
  • bus_ter
    bus_ter Posts: 337
    possibly a slightly longer chain. As said above I would ideally be looking to change to chain at the same time, so you can resize the new one. Be aware that Shimano document a different way to measure up an 11-28 chain length than with a smaller range cassette.

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