Shimano 105 rear derailleur weird specs

Discussion in 'Cycling Equipment' started by Rick Onanian, Aug 9, 2003.

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  1. Rick Onanian

    Rick Onanian Guest

    I'm looking at Shimano's website, considering a triple crankset for my 2001 Giant TCR2, stock all
    105 double.

    I'm trying to figure out how little I can get away with changing to put a triple on here.

    I can see that I'll need [obviously] a crankset and a front derailleur, but I wonder if I can get
    away with no new rear derailleur.

    How about, instead of a triple, compatibility with a mountain bike rear derailleur and then I use a
    really wide ratio cassette? I'd rather have the triple, but are Shimano road shifters compatible
    with Shimano MTB rear derailleurs?

    I think I don't understand a few terms. Here's what the site says about 105 double and triple rear
    derailleurs:

    Rear derailleur for double cranksets: Total Capacity: 37t Front Difference: 22t

    Rear derailleur for triple cranksets: Total Capacity: 29t Front Difference: 14t

    Maybe I don't understand the terminology, but I figured that the capacity is the amount of chain
    slack that the derailleur can take up, and the front difference is the largest difference in
    chainring that the rear derailleur can swallow suddenly (though I'm sure I'm wrong about that, I
    think I'm right about capacity).

    Everything else is the same (except the one for triples weighs a few more grams). Info from:
    http://bike.shimano.com/Road/105/componenttemplate.asp?partnumber=RD-5501- SS-S
    http://bike.shimano.com/Road/105/componenttemplate.asp?partnumber=RD-5501- GS-S

    Or, in tiny URLs: Double -- http://tinyurl.com/jilr Triple -- http://tinyurl.com/jilp

    --
    Rick Onanian
     
    Tags:


  2. Grenouil

    Grenouil Guest

    "Rick Onanian" <[email protected]> wrote in message news:eek:[email protected]...
    >
    > I'm looking at Shimano's website, considering a triple crankset for my 2001 Giant TCR2, stock all
    > 105 double.
    >
    > I'm trying to figure out how little I can get away with changing to put a triple on here.
    >
    > I can see that I'll need [obviously] a crankset and a front derailleur, but I wonder if I can get
    > away with no new rear derailleur.
    >
    > How about, instead of a triple, compatibility with a mountain bike rear derailleur and then I use
    > a really wide ratio cassette? I'd rather have the triple, but are Shimano road shifters compatible
    > with Shimano MTB rear derailleurs?
    >
    > I think I don't understand a few terms. Here's what the site says about 105 double and triple rear
    > derailleurs:
    >
    > Rear derailleur for double cranksets: Total Capacity: 37t Front Difference: 22t
    >
    > Rear derailleur for triple cranksets: Total Capacity: 29t Front Difference: 14t
    >
    > Maybe I don't understand the terminology, but I figured that the capacity is the amount of chain
    > slack that the derailleur can take up, and the front difference is the largest difference in
    > chainring that the rear derailleur can swallow suddenly (though I'm sure I'm wrong about that, I
    > think I'm right about capacity).
    >

    Rick - read the 'oracle' - Sheldon Brown's site at http://www.sheldonbrown.com/harris/index.html The
    glossary and articles will provide all the information you're looking for....

    You can use a double RDR with a triple crank, but depending on how you size the chain you could have
    some slack when using the smallest ring and some of the smaller rear sprockets, or a nasty
    experience when you inadvertently try to use the largest ring and the largest sprocket if the chain
    is too short. Probably better to get a triple RDR.

    An alternative to a triple is to use a 'wider' cassette and/or smaller chainrings. The largest rear
    sprocket for most 'road' dérailleurs according to the Shimano spec is 27T, but lots of people report
    using 30 or even 32 - the disadvantage is bigger gaps between adjacent sprockets.

    The smallest chainring you can use on a 130mm BCD crank like the Shimano 105 is 38T, so to go
    smaller you'll need a new double crank with a smaller BCD.
     
  3. G Huang

    G Huang Guest

    Rick Onanian wrote:
    >
    > I think I don't understand a few terms. Here's what the site says about 105 double and triple rear
    > derailleurs: ...

    If you download the service instruction in pdf on the same page, you'll see that it all makes sense.
    The web page erroneously swapped the numbers between SS and GS.
     
  4. Rick Onanian

    Rick Onanian Guest

    On Sat, 9 Aug 2003 17:06:15 -0500, Grenouil <[email protected]> wrote:
    > Rick - read the 'oracle' - Sheldon Brown's site at http://www.sheldonbrown.com/harris/index.html

    Of course...I never thought to look there for routine info, just the wacky stuff!

    > You can use a double RDR with a triple crank, but depending on how you size the chain you could
    > have some slack when using the smallest ring and some of the smaller rear sprockets, or a nasty
    > experience when you inadvertently try to use the largest ring and the largest sprocket if the
    > chain is too short. Probably better to get a triple RDR.

    I think I can shift carefully. Do I dare find out?

    > An alternative to a triple is to use a 'wider' cassette and/or smaller chainrings. The largest
    > rear sprocket for most 'road' dérailleurs according to the Shimano spec is 27T, but lots of people
    > report using 30 or even 32 - the disadvantage is bigger gaps between adjacent sprockets.

    I can handle the wide ratios. I don't need 9 gears all a single tooth (or two) apart from eachother.

    > The smallest chainring you can use on a 130mm BCD crank like the Shimano 105 is 38T, so to go
    > smaller you'll need a new double crank with a smaller BCD.

    Hmm...I could put a wider cassette and a new double crankset with a smaller small ring...that may be
    an option.

    --
    Rick Onanian
     
  5. Rick Onanian

    Rick Onanian Guest

    On Sat, 09 Aug 2003 18:09:24 -0400, G Huang <[email protected]_bell-labs.com> wrote:
    > see that it all makes sense. The web page erroneously swapped the numbers between SS and GS.

    I was afraid that was the case.

    --
    Rick Onanian
     
  6. Bruce

    Bruce Guest

    Triple crank & BB, triple front der.... You will also need a new left brifter to shift the triple.

    If a wider cluster might fit your needs you can use a 12-27 with the stock 105, and maybe up to a
    30. Or just switch the rear derailer to a MTBike (XT or LX or ...) and use a 12-34. That's what I do
    with my Dura-Ace setup when I want to tour with some extra baggage. I use a 12-34 w/ a 50-38, and
    only switch the rear derailer. The 12-34 has very even ratios of 10 to 15%.
    12-14-16-18-20-23-26-30-34

    15.4% = ln(14/12)
    16.4%
    17.4%
    18.5%
    19.%
    20.3%
    21.3%
    22.5%

    -Bruce

    "Rick Onanian" <[email protected]> wrote in message news:eek:[email protected]...
    >
    > I'm looking at Shimano's website, considering a triple crankset for my 2001 Giant TCR2, stock all
    > 105 double.
    >
    > I'm trying to figure out how little I can get away with changing to put a triple on here.
    >
    > I can see that I'll need [obviously] a crankset and a front derailleur, but I wonder if I can get
    > away with no new rear derailleur.
    >
    > How about, instead of a triple, compatibility with a mountain bike rear derailleur and then I use
    > a really wide ratio cassette? I'd rather have the triple, but are Shimano road shifters compatible
    > with Shimano MTB rear derailleurs?
    >
    > I think I don't understand a few terms. Here's what the site says about 105 double and triple rear
    > derailleurs:
    >
    > Rear derailleur for double cranksets: Total Capacity: 37t Front Difference: 22t
    >
    > Rear derailleur for triple cranksets: Total Capacity: 29t Front Difference: 14t
    >
    > Maybe I don't understand the terminology, but I figured that the capacity is the amount of chain
    > slack that the derailleur can take up, and the front difference is the largest difference in
    > chainring that the rear derailleur can swallow suddenly (though I'm sure I'm wrong about that, I
    > think I'm right about capacity).
    >
    > Everything else is the same (except the one for triples weighs a few more grams). Info from:
    > http://bike.shimano.com/Road/105/componenttemplate.asp?partnumber=RD-5501- SS-S
    > http://bike.shimano.com/Road/105/componenttemplate.asp?partnumber=RD-5501- GS-S
    >
    > Or, in tiny URLs: Double -- http://tinyurl.com/jilr Triple -- http://tinyurl.com/jilp
    >
    >
    > --
    > Rick Onanian
     
  7. "Bruce" <[email protected]> wrote in message news:[email protected]...
    > Triple crank & BB, triple front der.... You will also need a new left brifter to shift the triple.
    >
    > If a wider cluster might fit your needs you can use a 12-27 with the stock 105, and maybe up to a
    > 30. Or just switch the rear derailer to a MTBike (XT or LX or ...) and use a 12-34. That's what I
    > do with my Dura-Ace setup when I want to tour with some extra baggage. I use a 12-34 w/ a 50-38,
    > and only switch the rear derailer. The 12-34 has very even ratios of 10 to 15%.
    > 12-14-16-18-20-23-26-30-34
    >
    > 15.4% = ln(14/12)
    > 13.4%
    > 11.4%
    > 10.5%
    > 14.%
    > 12.3%
    > 14.3%
    > 12.5%
    >
    > -Bruce

    I'm new to this. Why the need to use natural logs in the above calculation? What's wrong with simple
    ratios between adjacent pairs?

    Cheers
    --
    M Stewart Milton Keynes, UK www.megalith.freeserve.co.uk/oddimage.htm
     
  8. Bruce

    Bruce Guest

    "Malcolm Stewart" <[email protected]> wrote in message
    news:[email protected]...
    > "Bruce" <[email protected]> wrote in message news:[email protected]...
    ..... The 12-34 has very even ratios of 10 to 15%.
    > > 12-14-16-18-20-23-26-30-34
    > >
    > > 15.4% = ln(14/12)
    > > 13.4%
    > > 11.4%
    > > 10.5%
    > > 14.%
    > > 12.3%
    > > 14.3%
    > > 12.5%
    > >
    > > -Bruce
    >
    > I'm new to this. Why the need to use natural logs in the above
    calculation?
    > What's wrong with simple ratios between adjacent pairs?
    >
    > Cheers
    > --
    > M Stewart Milton Keynes, UK www.megalith.freeserve.co.uk/oddimage.htm
    >
    >
    >

    Q: Why the need to use natural logs in the above calculation?
    R: The beauty of symmetry:

    18/20 = 9/10 = 0.90 = -10% change
    19/18 = 10/9 = 1.111 = 11.1% change.
    ln(20/18) = minus ln(18/20) = 0.10536 = 10.5%

    While I can do the first two calculations w/o computer assitance (and hence while riding) I perfer
    the symmetric choice. That way when I downshift from the 18 to the 20 it's the same change as when I
    upshift from the 20 to the
    18.

    Note the key word here is 'prefer'. Choose which method you prefer.

    -Bruce pure mathematician since age 7.
     
  9. "Rick Onanian" <[email protected]> wrote in message news:eek:[email protected]...
    > On Sat, 9 Aug 2003 17:06:15 -0500, Grenouil
    <[email protected]>
    > wrote:
    > > Rick - read the 'oracle' - Sheldon Brown's site at http://www.sheldonbrown.com/harris/index.html
    >
    > Of course...I never thought to look there for routine info, just the wacky stuff!
    >
    > > You can use a double RDR with a triple crank, but depending on how you size the chain you could
    > > have some slack when using the smallest ring and some of the smaller rear sprockets, or a nasty
    > > experience when you inadvertently try to use the largest ring and the largest sprocket if the
    > > chain is too short. Probably better to get a triple RDR.
    >
    > I think I can shift carefully. Do I dare find out?

    Don't risk it -- one day you may forget and have a serious problem.

    If the setup you desire is close to the capacity of your current derailleur, then I think you should
    set the bike up with a triple, a sufficiently long chain to handle the biggest cog and biggest ring,
    and the current derailleur, and just see how it works. If the chain is way too slack in the smallest
    cog/ring combo you would frequently use (this might not be the smallest cog and smallest ring -- if
    you go into the gear combo by accident it's not a big problem), then get the new derailleur. If the
    current rear derailleur can handle things, great, you saved some money.

    JT

    --
    *******************************************
    NB: reply-to address is munged

    Visit http://www.jt10000.com
    *******************************************
     
  10. spamsink-<< I'm looking at Shimano's website, considering a triple crankset for my 2001 Giant TCR2,
    stock all 105 double.

    I'm trying to figure out how little I can get away with changing to put a triple on here. >><BR><BR>

    BB, crank and front der and a little 'imaginative' chain length, meaning perhaps a little short...

    << How about, instead of a triple, compatibility with a mountain bike rear derailleur and then I use
    a really wide ratio cassette? >><BR><BR>

    yep, can use to about a 30t..for bigger, you really need a long cage rear der-like 105 or Deore..

    << I'd rather have the triple, but are Shimano road shifters compatible with Shimano MTB rear
    derailleurs? >><BR><BR>

    yep....

    Peter Chisholm Vecchio's Bicicletteria 1833 Pearl St. Boulder, CO, 80302
    (303)440-3535 http://www.vecchios.com "Ruote convenzionali costruite eccezionalmente bene"
     
  11. bruce-<< Triple crank & BB, triple front der.... You will also need a new left brifter to shift the
    triple. >><BR><BR>

    If the setup is 9s...the left shifter is double and triple compatible..think in 2001 it was...

    Peter Chisholm Vecchio's Bicicletteria 1833 Pearl St. Boulder, CO, 80302
    (303)440-3535 http://www.vecchios.com "Ruote convenzionali costruite eccezionalmente bene"
     
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