Chain length

Hi, I've just installed a 105 11 speed groupset to upgrade from an 8 speed claris. It's an 11-30 with a mid size rear deraillier and 50-34 chainset. I purchased a new chain and did the method where you put the chain on the largest cog front and back etc. but no matter how many links I remove I'm either too slack on the small chainring or too tight on the large. Just wondering if theres anything I've missed here? As it stands I can shift to the largest cog front and back but it wont shift from there and if I add a link then the smallest cog front and smallest 3 cogs on the casette are unusable as the chain is too slack. I'm guessing too slack is better than too tight as I won't ever use the 12th gear but just wondering why I can't get it right. Any advice would be very much appreciated even if it's just confirmation to leave it as it is because the bike (Trek Domane AL2) is shifting fine on the road.


  • N0bodyOfTheGoat
    N0bodyOfTheGoat Posts: 5,845
    IIRC, the 105 7000 SS short cage mechs officially support up to and including 30T.
    2020 Voodoo Marasa
    2017 Cube Attain GTC Pro Disc 2016
    2016 Voodoo Wazoo
  • Right, so you cant have a mid cage mech with an 11-30? Well you can but you end of with this problem
  • arlowood
    arlowood Posts: 2,561
    Use the calculator in the link below to double check you have the right chain length. I've used it for years and it has always worked for me.

    Your medium cage derailleur should work with an 11-30 cassette. The comment above about the short cage working is OK but the medium cage should be ideal for this set up. I can't understand why you are having the issues you describe. Maybe a couple of pics might help us guide you more confidently.
  • wongataa
    wongataa Posts: 1,001
    Download the installation instructions for you drivetrain from Shimano and follow their instructions for setting the chain length.
  • s_j_pwmb
    s_j_pwmb Posts: 75
    edited July 2020
    Shimano’s guidance is exactly as you’ve done, plus two links (a pair) around the big-big combination so you should be fine.

    I’m using a Shimano GS derailleur and a KMC chain which uses a quick-link which means I’ve had to add an extra link into the length over what I’d run if using a pin to connect the ends (so I have an extra 1.5 inches in total). As I’m running a 11-34 cassette I also have an extra 2 inches of chain over what you’ll have on your 11-30, despite this “extra” 3.5 inches it works flawlessly from 50/11 to 34/34, being neither too tight nor too slack.

    Two thoughts spring to mind, is your B Screw adjusted correctly for the 30 tooth cog (see below), and are you sure the derailleur is mounted correctly on the hanger? I have (embarrassingly) fitted a derailleur with the hanger-stop knob between the two ridges on the derailleur rather than below them which affected the angle-of-dangle (The “Z” knob in the second picture).

  • pilot_pete
    pilot_pete Posts: 2,120
    Pictures required really as if you have done everything s_j has said then all should work. Can’t understand what you’ve done wrong from the description alone...

  • The Rookie
    The Rookie Posts: 27,812
    The 105 mid cage has a capacity of 39, your setup needs 35 so the cage is long enough IF its installed correctly.
    So sounds like an install issue, reset the chainlength properly and then look at the instal', random shortening of the chain can end with catastrophic and expensive consequences.
    Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.
  • Thank you to everyone taking the time to assist me on this. I had installed it incorrectly. this was old position, as someone suggested it was in the middle
    I have now moved it to the correct position (I think)
    I still think the chain is too short though but like your advice to confirm this. This was what I was facing with the rear mech incorrectly installed (50-30)
    now this is the current situation (34-11)
    So would say Im still short? I have the rest of the chain to add but will adding the links back in effect the integrity of the chain? Do I just use the chain link tool in reverse so I'm pushing the link back in rather than out? I Realise I wont be cross chaining as a rule but sometimes I find myself in these gears and although I quickly get out of them Im aware it would only take a second to do some damage.

    Many Thanks

  • lesfirth
    lesfirth Posts: 1,382
    edited July 2020
    Cross chaining is not something you or your drivetrain die from. The most serious consequence is accelerated wear when done excessively. A quick bit will not do any damage.
    Your set up in the last photos looks fine. Any problems you have with gear changing are not related to your chain length.
    Now stop thinking and ride the bl00dy bike.
  • 😂😂 you've got a valid point, it's been on the stand more than on the road recently. Thanks for the advice.
  • Ben6899
    Ben6899 Posts: 9,686
    edited July 2020
    Looks good now, Dave. :)

    Bikes: Donhou DSS4 Custom | Condor Italia RC | Gios Megalite | Dolan Preffisio | Giant Bowery '76
  • Ben6899 said:

    Looks good now, Dave. :)

    Thank you, looking forward to getting it on the road again 👍