fitting a compact chainset

el_vino
el_vino Posts: 64
edited May 2009 in Road beginners
I am planning to remove the standard 105 chainset on my bike and replace with a compact. I would like to do the work myself and have access to the hollowtech tool. I don't need to change the BB, just the chainset. What other adjustments am i likely to have to make

i.e. Will I need to shorten the chain if so by how much
what derauiler adjustments will be needed (doesn't look like height adjustment is possible)
what about cable lenght?

thanks
EV

Comments

  • Anonymous
    Anonymous Posts: 79,667
    Adjust deraillieur height so the outside edge of the derr has about 1-2mm gap from the chainset then fettle cable length as necessary.

    You may also need to take a few links out of the chain.
  • Monty Dog
    Monty Dog Posts: 20,614
    Assuming you're fitting an HT2 or MegaExo crank, the BB can stay put. Slide the new one in, fit non-drive crank, tighten botls/ adjust bearings in accordance with instructions. You should be able to get away with your current front mech - just drop it a few mm.
    Make mine an Italian, with Campagnolo on the side..
  • el_vino
    el_vino Posts: 64
    Thanks for the response guys, Its the lowering the height of my front mech that looks difficult, on other bikes I've owned (all mtbs) you would loosen the allen bolt on the collar and moive up or down, however this mech seems to be bolted into 2 threaded holes in the frame so not immediatly clear how to adjust mech height.
    thanks
    EV
  • andy_wrx
    andy_wrx Posts: 3,396
    Is there not a plate bolted into the frame, then the mech itself bolted to the plate, bolted through a slot so it can be moved up & down ?
  • el_vino
    el_vino Posts: 64
    Will look a bit closer this evening, this is my first road bike since the 1980s so I have a bit of catching up to do on the mechanical side of things!
    cheers
    EV
  • ohlala!
    ohlala! Posts: 121
    Why do you not try just changing the chainrings, Stronglight has 130 PCD on 50T and 34T chainrings. It's easier, faster and cheaper to change. You'd still have to adjust your derailleur after though.
  • el_vino
    el_vino Posts: 64
    Sorry but what does 130 PCD stand for? And is there any downside to changing the rings as opposed to the entire chainset?
    EV
  • Mister W
    Mister W Posts: 791
    PCD - Pitch Circle Diameter. It's a measure of the spacing of the chainring bolts. Most standard double chainsets have a PCD of 130. Most compact chainsets have a PCD of 110.

    I'm suprised that you can get a 34T ring with a 130 PCD. Can you give us a link, ohlala! ?

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