Compact chainsets

Discussion in 'UK and Europe' started by MartinM, Jan 19, 2006.

  1. MartinM

    MartinM Guest

    Following on from a discussion about these; I see CW have got a whole
    article about them. However none of them seem to go below 34T. This is
    not that much less than the 39T on my current double. The alternative
    to fitting one seems to be using the bottom two rings only of a triple,
    although I can see possible issues with the front mech. Does anyone
    have any experience of doing this? I only want to fit one for La
    Marmotte and hopefully cascade it down afterwards. Would the top two of
    an MTB one be easier?

    TIA
     
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  2. David Martin

    David Martin Guest

    MartinM wrote:
    > Following on from a discussion about these; I see CW have got a whole
    > article about them. However none of them seem to go below 34T. This is
    > not that much less than the 39T on my current double. The alternative
    > to fitting one seems to be using the bottom two rings only of a triple,
    > although I can see possible issues with the front mech.


    I thought I had chain line problems till I realised it was the vertical
    line from my 34t compact inner that was the problem. Unfortunately it
    is a braze on fitting so I might have to do a bit of hunting for a new
    front mech with a longer cage.

    34t makes a significant difference over 39t (equiv to 28-32 jump at the
    rear) IME. Of course you could bite the bullet and get a TA Vega or
    Carmina which would then let you put on almost anything you want.

    > Does anyone
    > have any experience of doing this? I only want to fit one for La
    > Marmotte and hopefully cascade it down afterwards. Would the top two of
    > an MTB one be easier?


    Probably. I find 48/34 to be fine and climb most anything with that and
    a suitable (12-26 or 12-28) cassette in back.

    ...d
     
  3. Arthur Clune

    Arthur Clune Guest

    MartinM wrote:
    > Following on from a discussion about these; I see CW have got a whole
    > article about them. However none of them seem to go below 34T. This is
    > not that much less than the 39T on my current double.


    In practice it's a useful drop. 34x26 is a fairly low gear on a road bike
    (same as 30x23 near enough)

    Combine with a 13-28 cassette for a lower gear if you want. You can
    always do what I did and turn a 13-up cassette into a 12-up cassette
    with a jump at the top end by replacing the 13-tooth lockring with a
    12. I used a Campag 9 speed block that looked like this

    12-14-15 ... - 26

    The gap at the top doesn't really matter since in the Alps.

    > The alternative
    > to fitting one seems to be using the bottom two rings only of a triple,
    > although I can see possible issues with the front mech. Does anyone
    > have any experience of doing this? I only want to fit one for La
    > Marmotte and hopefully cascade it down afterwards. Would the top two of
    > an MTB one be easier?


    As I said before, I think you'll be undergeared doing this. You'll probably
    have chainline issues as well since a MTB triple is designed to work on a
    longer bottom bracket than a double.

    Arthur

    --
    Arthur Clune
     
  4. MartinM

    MartinM Guest

    Arthur Clune wrote:

    > In practice it's a useful drop. 34x26 is a fairly low gear on a road

    bike
    > (same as 30x23 near enough)


    30x23 is what I have on my Audax bike, not really low enough for last
    gasp climbs

    > Combine with a 13-28 cassette for a lower gear if you want. You can
    > always do what I did and turn a 13-up cassette into a 12-up cassette
    > with a jump at the top end by replacing the 13-tooth lockring with a
    > 12. I used a Campag 9 speed block that looked like this
    >
    > 12-14-15 ... - 26


    I used a 21-28 jump on a botched cassette a couple of years ago before
    the triple; it was virtually impossible to get out of bottom gear on a
    steep climb



    > As I said before, I think you'll be undergeared doing this.


    I know you have, the alternatives are;

    compact

    use the triple bike, neither give me much of an advantage over the
    existing 39x26. Fortunately I have a band on front mech so can drop it
    down as required. Presumably using a 28 on the back would cause chain
    length issues?

    what are the chainline issues? I would only be using the little ring on
    the top 3 gears?
     
  5. Arthur Clune

    Arthur Clune Guest

    MartinM wrote:
    >
    > I used a 21-28 jump on a botched cassette a couple of years ago before
    > the triple; it was virtually impossible to get out of bottom gear on a
    > steep climb


    That's why I say put the jump at the top end of the cassette. You'd not
    want a large jump in the low gears anyway when climbing.

    > compact
    >
    > use the triple bike, neither give me much of an advantage over the
    > existing 39x26. Fortunately I have a band on front mech so can drop it
    > down as required. Presumably using a 28 on the back would cause chain
    > length issues?


    Don't see why. A short cage mech is fine with a 28 and the extra chain
    you need for the 28 should be compenstated for by the smaller large
    ring.

    > what are the chainline issues? I would only be using the little ring on
    > the top 3 gears?


    It may (or may not) put the little ring too close to the frame. You'd have
    to see.

    --
    Arthur Clune
     
  6. In article <[email protected]>,
    MartinM ([email protected]) wrote:
    > Following on from a discussion about these; I see CW have got a whole
    > article about them. However none of them seem to go below 34T. This is
    > not that much less than the 39T on my current double. The alternative
    > to fitting one seems to be using the bottom two rings only of a triple,
    > although I can see possible issues with the front mech. Does anyone
    > have any experience of doing this? I only want to fit one for La
    > Marmotte and hopefully cascade it down afterwards. Would the top two of
    > an MTB one be easier?


    IIRC road bike front mechs /can/ be a little fractious when asked to
    play with MTB-size "big" chainrings and in the case of $himano, road
    front mechs have different cable pull requirements to MTB ones. So
    getting STI shifters to co-operate with an MTB front derailleur /may/
    also be an issue.

    If you can find a cheap Stronglight chainset with 86 mm BCD rings - such
    as the 80 or 99 - you could assemble a 28/nn double, where nn is almost
    anything you like. I used to run a 28/42 setup with a 99 years before
    these so-called "compact" wossnames came onto the market[1]. This,
    admittedly, was because as a Penniless Student Oaf I could not amass
    sufficient credits to acquire a TA Cyclotourise, Stronglight 49D or one
    of those new-fangled Red S 74/110 triples.

    If you /can't/ find one, I am willing to rent out the one[2] from my
    fixer for a suitable fee ;-)

    1 - So /I/ invented them, and all these manufacturers must give me lots
    of money immediately
    2 - Though you'd need new chainrings, obv.

    --
    Dave Larrington - <http://www.legslarry.beerdrinkers.co.uk/>
    Dead journalists make excellent objets d'art.
     
  7. David Martin

    David Martin Guest

    Arthur Clune wrote:
    > Don't see why. A short cage mech is fine with a 28 and the extra chain
    > you need for the 28 should be compenstated for by the smaller large
    > ring.


    I'd check the mech. It isn't so much the cage length as the body
    length. My Sante one is not rated above 23 (IIRC) and will not do 26
    (though will do 25).

    ...d
     
  8. MSeries

    MSeries Guest

    Dave Larrington wrote:
    > In article <[email protected]>,
    > MartinM ([email protected]) wrote:
    > > Following on from a discussion about these; I see CW have got a whole
    > > article about them. However none of them seem to go below 34T. This is
    > > not that much less than the 39T on my current double. The alternative
    > > to fitting one seems to be using the bottom two rings only of a triple,
    > > although I can see possible issues with the front mech. Does anyone
    > > have any experience of doing this? I only want to fit one for La
    > > Marmotte and hopefully cascade it down afterwards. Would the top two of
    > > an MTB one be easier?

    >
    > IIRC road bike front mechs /can/ be a little fractious when asked to
    > play with MTB-size "big" chainrings and in the case of $himano, road
    > front mechs have different cable pull requirements to MTB ones. So
    > getting STI shifters to co-operate with an MTB front derailleur /may/
    > also be an issue.
    >


    Nah, my 105 triple front mech works fine with my 48/38/28 Deore
    chaniset. BUT I don't use STi or indexed front on this bike.
     
  9. MartinM

    MartinM Guest

    Arthur Clune wrote:

    > It may (or may not) put the little ring too close to the frame. You'd have
    > to see.


    That's exactly what I was worried about; although I could buy a wider
    BB, this could also be re-cycled (as skogTM) has a good record of
    wrecking these IMX despite being "sealed"
     
  10. MartinM

    MartinM Guest

    David Martin wrote:

    > Arthur Clune wrote:
    > > Don't see why. A short cage mech is fine with a 28 and the extra chain
    > > you need for the 28 should be compenstated for by the smaller large
    > > ring.

    >


    breaks the rules about chain length a bit Shirley in that you won't be
    able to use every front with every back cog (as if you'd ever want to).
    My Ribble was converted from a double to a triple without needing a
    long cage rear mech (max 50x13 min 30x23). I got a "audax specific"
    50/40/30 Ofmega chainset from sjs, very pleased with it and all alloy
    unlike Sora.
     
  11. MSeries

    MSeries Guest

    MartinM wrote:
    > Following on from a discussion about these; I see CW have got a whole
    > article about them. However none of them seem to go below 34T. This is
    > not that much less than the 39T on my current double. The alternative
    > to fitting one seems to be using the bottom two rings only of a triple,
    > although I can see possible issues with the front mech. Does anyone
    > have any experience of doing this? I only want to fit one for La
    > Marmotte and hopefully cascade it down afterwards. Would the top two of
    > an MTB one be easier?
    >
    > TIA


    I have a Deore triple with 48/38/28 rings (110mm PCD), you are
    suggesting something like --/42/28 on such a device ? I use a 105 front
    mech. I did have 50/36 and a 105 double front mech worked fine. Non
    indexed of course, why would anyone need to index two positions, even
    with three it really isn't hard to get it right.
     
  12. MartinM

    MartinM Guest

    MSeries wrote:

    why would anyone need to index two positions, even
    > with three it really isn't hard to get it right.


    because they have STI's? ;-) and the ratchet type as well so no use
    with a triple.
     
  13. MSeries

    MSeries Guest

    MartinM wrote:
    > David Martin wrote:
    >
    > > Arthur Clune wrote:
    > > > Don't see why. A short cage mech is fine with a 28 and the extra chain
    > > > you need for the 28 should be compenstated for by the smaller large
    > > > ring.

    > >

    >
    > breaks the rules about chain length a bit Shirley in that you won't be
    > able to use every front with every back cog (as if you'd ever want to).
    > My Ribble was converted from a double to a triple without needing a
    > long cage rear mech (max 50x13 min 30x23). I got a "audax specific"
    > 50/40/30 Ofmega chainset from sjs, very pleased with it and all alloy
    > unlike Sora.


    Audax Specific ? Like it knows about route sheets and controls and min
    and max speeds ?
     
  14. In article <[email protected]>,
    MSeries ([email protected]) wrote:
    >
    > Dave Larrington wrote:


    > > IIRC road bike front mechs /can/ be a little fractious when asked to
    > > play with MTB-size "big" chainrings and in the case of $himano, road
    > > front mechs have different cable pull requirements to MTB ones. So
    > > getting STI shifters to co-operate with an MTB front derailleur /may/
    > > also be an issue.
    > >

    >
    > Nah, my 105 triple front mech works fine with my 48/38/28 Deore
    > chaniset. BUT I don't use STi or indexed front on this bike.


    48 is quite large by current MTB standards, thobut. They mostly seem to
    be 42 or 44 these days.

    --
    Dave Larrington - <http://www.legslarry.beerdrinkers.co.uk/>
    Ha ha, you fool! You've fallen victim to one of the classic blunders!
    The most famous is "Never get involved in a land war in Asia"
     
  15. MartinM

    MartinM Guest

    Dave Larrington wrote:
    > In article <[email protected]>,
    > MSeries ([email protected]) wrote:
    > >
    > > Dave Larrington wrote:

    >
    > > > IIRC road bike front mechs /can/ be a little fractious when asked to
    > > > play with MTB-size "big" chainrings and in the case of $himano, road
    > > > front mechs have different cable pull requirements to MTB ones. So
    > > > getting STI shifters to co-operate with an MTB front derailleur /may/
    > > > also be an issue.
    > > >

    > >
    > > Nah, my 105 triple front mech works fine with my 48/38/28 Deore
    > > chaniset. BUT I don't use STi or indexed front on this bike.

    >
    > 48 is quite large by current MTB standards, thobut. They mostly seem to
    > be 42 or 44 these days.


    Thanks everyone for all the advice; still pondering. The options seem
    to be;

    Stronglight compact chainset (for one ride) 49.99

    Buy a 105 triple groupset and fit to bike, cascade old groupset to (as
    yet still in Dreamland) 2007 Audax bike

    Go back to plan A, take the triple Audax bike and suffer slowly (with
    secret weapon 26T cassette)

    The Inland Revenue seem to be having the final say ;-( Working Families
    tax credit (FSVO credit)
     
  16. Arthur Clune

    Arthur Clune Guest

    MartinM wrote:
    >
    > Stronglight compact chainset (for one ride) 49.99


    You might find, like me, that you like it so much you just
    leave it on all the time. I run 38/48 normally now with a
    34 inner ring fitted for long and steep rides.

    > Go back to plan A, take the triple Audax bike and suffer slowly (with
    > secret weapon 26T cassette)


    Option 3?

    Put gears from Audax bike onto light bike. If you can do the
    work yourself, this might be an option.

    Arthur

    --
    Arthur Clune
     
  17. MartinM

    MartinM Guest

    Arthur Clune wrote:
    > MartinM wrote:
    > >
    > > Stronglight compact chainset (for one ride) 49.99

    >
    > You might find, like me, that you like it so much you just
    > leave it on all the time. I run 38/48 normally now with a
    > 34 inner ring fitted for long and steep rides.
    >
    > > Go back to plan A, take the triple Audax bike and suffer slowly (with
    > > secret weapon 26T cassette)

    >
    > Option 3?
    >
    > Put gears from Audax bike onto light bike. If you can do the
    > work yourself, this might be an option.


    did think of this, it is the cheapest and easiest option, just swap
    front mech/ chainset and STI unit (RX100/RSX) can restrict the Audax
    bike to flat rides in the interim. Thanks

    May need to use the Audax bike for a rack (depends what Caradice the
    birthday fairy brings).
     
  18. David Martin wrote:

    > MartinM wrote:
    >
    > I thought I had chain line problems till I realised it was the vertical
    > line from my 34t compact inner that was the problem. Unfortunately it
    > is a braze on fitting so I might have to do a bit of hunting for a new
    > front mech with a longer cage.
    >


    Campag seem to have introduced some new "compact" double front mechs
    with a much deeper inner cage plate [1], presumably to take care of
    efficient upshifts between rings with a wide difference in no. of teeth
    like 34T to 50T, which sound as though they'd do the job well. Don't
    know if there are any compatibility issues, though (e.g. suitable for
    10sp chains only?).

    David Belcher

    [1] See, for instance, probikekit.com's full-page ads in CW for photos
    showing cage design.
     
  19. Arthur Clune

    Arthur Clune Guest

    MartinM wrote:

    > May need to use the Audax bike for a rack (depends what Caradice the
    > birthday fairy brings).


    It's the Marmotte. Why on earth would you need a rack?

    If you really think you need a rack, you are taking far too much.

    Arthur

    --
    Arthur Clune
     
  20. MartinM

    MartinM Guest

    Arthur Clune wrote:
    > MartinM wrote:
    >
    > > May need to use the Audax bike for a rack (depends what Caradice the
    > > birthday fairy brings).

    >
    > It's the Marmotte. Why on earth would you need a rack?


    only to get from the airport, will be stripping everything off at Bourg
    (rack, light brackets,liposuction) although the bus is an option.
     
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