Swapping double chainset for compact

star_rover
star_rover Posts: 318
edited September 2007 in Workshop
Want to swap my double chainset (shimano 105) for a compact. To save cash (and learn something) I plan to do it myself.
A few questions:
Will I need a new bottom bracket?
Will I need a new chain?
Will I need a new front mech (I hope not)?

Any other pitfalls I should look out for?

cheers

Comments

  • feno46
    feno46 Posts: 66
    I was going to ask just the same questions,

    I'm hoping to swap a campy veloce exa drive 53/39 for a veloce ultra drive compact.

    I know the bottom bracket on the ultra drive is different with outboard cups.

    Hope I havent hilacked your thread.

    Maybe a good tech will have the answers.

    Pete
    Its how far !!
  • maddog 2
    maddog 2 Posts: 8,114
    depends what version your 105 is.

    If it uses outboard BB cups then one the the current Shimano compacts will slot straight in.

    If it's octalink then you'll either need a octalink compact or swap the BB for BB cups.

    Chain might need shortening a link or two - just use a SRAM powerlink

    Shimnao recommend using a standard double f. mech, so that'll be okay (I actually use a Campag compact mech, which'll work with a tweak)

    Other than that, if your mech is braze-on then check it'll drop down far enough (4-5mm is usually needed)
    Facts are meaningless, you can use facts to prove anything that's remotely true! - Homer
  • campagsarge
    campagsarge Posts: 434
    I seem to remember on another similar post someone saying that you should not need a new mech, Feno46 as the Campag standard one will work just fine.

    I also seem to remember that you may need a new chainset if going compact as the chain-ring bolts are closer together.

    I would do a search on this forum and see what you come up with as I reckon this has appeared somewhere before.
  • feno46
    feno46 Posts: 66
    campagsarge wrote:
    I seem to remember on another similar post someone saying that you should not need a new mech, Feno46 as the Campag standard one will work just fine.

    I also seem to remember that you may need a new chainset if going compact as the chain-ring bolts are closer together.

    I would do a search on this forum and see what you come up with as I reckon this has appeared somewhere before.


    Yes I am buying a new chainset, Veloce ultra torque, and was told by the seller I would need a new front mech, ??

    I am still unsure about the bottom bracket set up. The cups that are coming with the cranks, will they be used with the existing bearing.?
    Its how far !!
  • Monty Dog
    Monty Dog Posts: 20,614
    Assuming you have the correct BB/external bearing assembly then the answer is no, you don't need a new one. No you don't need a new chain - it just needs to be shorted by the differnece in large chainring sizes e/g 53-50 = 3 teeth i.e. 1 link. Finally, no you don't need a new front mech - most work OK but alignment is a bit more critical. For the Campag ultra torque cranks, the bearings are fitted to the crank spindle and the cups only bought seperately..
    Make mine an Italian, with Campagnolo on the side..
  • jimwin
    jimwin Posts: 208
    Pete

    I'm hoping to swap a campy veloce exa drive 53/39 for a veloce ultra drive compact.

    I know the bottom bracket on the ultra drive is different with outboard cups.

    Pete[unquote]

    Make sure you have a long reach 10mm hex key for clamping the two halves together. I did the same swap to get a better gear spread when climbing steep hills. Compacts are noticably different in use.

    - JimW
  • star_rover
    star_rover Posts: 318
    thanks chaps

    it does currently have the outboard BB cups and standard 105 front mech, so I reckon I'm all set.

    appreciate the quick replies

Categories