Changing a 50/34 chainring to a 53/39 question

Dan777
Dan777 Posts: 49
edited August 2009 in Workshop
hi,
i am assuming this is possible, but would the derailleur need to be moved up, and would you be able to move the derailleur up if the front derailluer appears to be bolted onto the frame rather than clamped on. the bike in question is a felt f4.

any help would be greatly appreciated, thanks.

Comments

  • freehub
    freehub Posts: 4,257
    Bolted? Is that the braze on with like a part welded onto the frame the mech screws to? I'm sure you can move them up. Yes the derailleur will need to be moved up.
  • Dan777
    Dan777 Posts: 49
    it looks like you describe yes. i was just worried it might weaken the frame if re bolted further up the frame
  • amaferanga
    amaferanga Posts: 6,789
    Are you talking about drilling a hole in the frame? Anyway, I think the BCD for the compact and standard rings will be different (130mm on a double, 110mm on a compact) so I don't think it'll be possible. I've never tried it though so could be wrong....
    More problems but still living....
  • skyd0g
    skyd0g Posts: 2,540
    amaferanga wrote:
    Are you talking about drilling a hole in the frame? Anyway, I think the BCD for the compact and standard rings will be different (130mm on a double, 110mm on a compact) so I don't think it'll be possible. I've never tried it though so could be wrong....

    I think the OP is looking to swop the entire chainset, not just the rings.
    Cycling weakly
  • Dan777
    Dan777 Posts: 49
    i would replace the 50/34 with 53/39, that ideally would be all i would replace. my only concern is moving the derailleur up, and if i did would it be possible without frame damage.
  • RedJohn
    RedJohn Posts: 272
    Should be no problem, loosen the bolt and slide it up in the slot (that's made for the purpose).

    Some front mechs are specifically made for compact or standard sizes of chainring so it may not work quite as slickly (should still work though).
  • amaferanga
    amaferanga Posts: 6,789
    skyd0g wrote:
    amaferanga wrote:
    Are you talking about drilling a hole in the frame? Anyway, I think the BCD for the compact and standard rings will be different (130mm on a double, 110mm on a compact) so I don't think it'll be possible. I've never tried it though so could be wrong....

    I think the OP is looking to swop the entire chainset, not just the rings.

    Oooops :oops:
    More problems but still living....
  • Pokerface
    Pokerface Posts: 7,960
    Dan777 wrote:
    i would replace the 50/34 with 53/39, that ideally would be all i would replace. my only concern is moving the derailleur up, and if i did would it be possible without frame damage.

    Just a note...

    You CAN get 53/39 rings with a 110BCD (to fit a compact chainset) - but they are hard to find.

    Don't just go out and buy ANY 53/39 rings as they won't fit your existing crank arms. You'll have to get aftermarket rings. I've done the swap myself and had to search around a bit to find something that worked.
  • neil_pcp
    neil_pcp Posts: 65
    do not touch anything that is directly attatched to the frame!!

    The piece of metal that the front mech is bolted to has a hole that is oval shaped and allows vertical adjustment just loosen the bolt at the front of the mech and slide it up 2mm which should be enough to accomodate a larger chainring

    http://techdocs.shimano.com/media/techd ... 673798.pdf

    see diagram the bolt you loosen is number 7 on the diagram which allows you to slide the mech up and down the bracket number 5/6. It is refered to as a braze on as traditionally this piece of metal was brazed onto a metal frame yours will be attatched with rivets or small bolts
    Neil
  • bexley5200
    bexley5200 Posts: 692
    overgeared 34 too small for most u surly can get a 39 t to fit that damed compact try a new cassette 11 23 first though thats what im doing
    going downhill slowly
  • RedJohn
    RedJohn Posts: 272
    bexley5200 wrote:
    overgeared 34 too small for most u surly can get a 39 t to fit that damed compact try a new cassette 11 23 first though thats what im doing

    I run a 50/11 top, I find it's too high and I almost never use it. Plan is to swap the 11-23 out for a 12-23, to get some closer ratios at the other end. I find I hunt back and forth between the 17 and 19 on flat-ish roads, so an 18 would be good.

    Of course you might easily be considerably fitter & stronger than me and be in a position to make use of a 53/12 or 50/11.

    Of course you could just pedal faster :-)

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