B-screw mods for road bike derailleurs (CX stuff)

Discussion in 'Parts 'n Stuff' started by takai, Oct 8, 2017.

  1. takai

    takai Eats Squid

    Ok, tried asking this on some road forums and they were all NFI due to it not being Durace etc

    Have Shimano 105 5700 setup on CX bike, running 1x10. Dont want to shell out for 1x11 and hydros just yet. Want bigger rear cluster. Wondering if its possible to do the B-screw mod on a 105 mech, like it is on the Shadow mechs to run larger rear clusters on 1x10 on the MTB.

    Considering this as i have a couple of spare 32T max rear clusters for the MTB, but no smaller NW chainrings spare.

    Not anywhere near the bike at the moment, so a bit hard to check. Anyone mucked around with this?

    Edit: Ugh, in wrong sub-forum. Anyone want to move it to Parts n Stuff.
    Last edited: Oct 8, 2017
  2. The Duckmeister

    The Duckmeister Eats Squid

    5700 got a mid-model update around 2012, which increased maximum sprocket capacity. Pre-'12 derailleurs officially have a limit of 28T, but some frames' hangers can put it a bit lower & give more clearance. 2012 model & later, post-tweak will fit a 32T out of the box. Official specs say you need the longer cage version to do it, but that's because they're assuming it'll be paired to a compact crankset with 16T chainring difference, and the total difference will push the short derailleur to its limit (but it will do it). The big cassette and tighter-range CX crankset will comfortably fit with a regular short late-model 5700 RD with no mods required.

    1x of course removes the chainring difference from the equation entirely.
  3. Haakon

    Haakon Not happy, Jan.

    Bloody roadies... I have never understood how they manage to ride with the stick so far up their arse.
  4. sane

    sane Likes Bikes and Dirt

  5. takai

    takai Eats Squid

    Thanks, found this https://www.amazon.com/Bicycle-Dera...=UTF8&qid=1507507243&sr=8-2&keywords=roadlink

    Appears to be the same thing, just unbranded.

    Also looking around it appears that i can use a 9sp MTB mech, as it has the same actuation ratio as the 10sp road shifters
  6. mtb101

    mtb101 Likes Bikes and Dirt

    probably wont ship to au, get the wolf tooth from mtbdirect, I've just put on a 11-42 x2 on friends cx works nicely no more whinging on the climbs.
  7. takai

    takai Eats Squid

    Ah, thats what i have a US dropbox for ;)

    Ill pick that up, but also have a play around with a XT M770 i have lying around. See if i can get a 11-36 on there. Its primarily for a lower gear so i can turn up to work somewhat less sweaty (new work is at the top of a climb), so a 36T should be enough..
  8. Calvin27

    Calvin27 Likes Bikes and Dirt

    Isn't the chainring easier to do?

    I run a 5700 Rd with 11-32 no mods.
  9. takai

    takai Eats Squid

    Easier != cheaper. Also more chain wrap at the front makes for more reliable NW.
  10. takai

    takai Eats Squid

    Right, 9sp rear mech and 10sp cluster works a treat:
  11. takai

    takai Eats Squid

    To confirm, this definitely works:

    Far easier than Bscrew mods, and lets me keep a good top gear as well as a broad range.

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