Is this gear combination allowed?

Discussion in 'Cycling Equipment' started by Telford, Jun 14, 2003.

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  1. Telford

    Telford Guest

    My touring bike currently has

    26-36-46 RSX crank 12-32 shimano "P' 8 sp. cass Deore LX rear derail RSX front derail RSX
    STI Shifters

    Can I put a 22 ring on the smaller one (I need to put little lower gear for loaded touring but short
    of changing the whole crank to something like Deore 22-32-46, may be I can just change only the
    small chain ring??

    I know there's ring-difference that is not allowed, just not sure how it will be for me.

    Thank you.
     
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  2. Telford wrote:
    > My touring bike currently has=20
    >=20
    > 26-36-46 RSX crank 12-32 shimano "P' 8 sp. cass Deore LX rear derail RSX front derail RSX STI
    > Shifters
    >=20 20
    > Can I put a 22 ring on the smaller one (I need to put little lower gear for loaded touring but
    > short of changing the whole crank to something like Deore 22-32-46, may be I can just change only
    > the small chain ring??
    >=20
    > I know there's ring-difference that is not allowed, just not sure how it will be for me.

    Your crank uses the 74 mm bolt circle diameter (BCD). This means that=20 the smallest chainring
    physically possible to fit it is 24 teeth.

    There would be no problem at all going to a 24, but 22 isn't possible=20 unless you replace
    the crank.

    Sheldon "Limits" Brown +-------------------------------------------------+
    | I will be appearing in the Midsummer Revels | Boston Children=92s Museum, June 20 | (I=92ll be
    | the front of the Dragon) | http://revels.org |
    +-------------------------------------------------+ Harris Cyclery, West Newton, Massachusetts Phone
    617-244-9772 FAX 617-244-1041 http://harriscyclery.com Hard-to-find parts shipped Worldwide
    http://captainbike.com http://sheldonbrown.com
     
  3. Matt O'Toole

    Matt O'Toole Guest

    "Sheldon Brown" <[email protected]> wrote in message
    news:[email protected]...

    > Your crank uses the 74 mm bolt circle diameter (BCD). This means that the smallest chainring
    > physically possible to fit it is 24 teeth.

    > There would be no problem at all going to a 24, but 22 isn't possible unless you replace
    > the crank.

    ...unless you can find an Avid Microdaptor, which lets you put 58mm BCD chainrings on a 74mm BCD
    crank. I doubt these are still being made, but someone's likely to be hoarding them somewhere.

    I ran 22T chainrings on my old Deore DX cranks for years, before "Compact Drive" cranks came out.

    Matt O.
     
  4. Andresmuro

    Andresmuro Guest

    There is something called a spider. It is an attachemnt that you use to reduce the bolt circle from
    74 to 58?? This will allow you to put a 20 or 22 teeth chainring. I had one, but I don't think I
    have it anymore. If I can find it, I'll let you have it for $10 plus shipping. But the chances of me
    finding it are slim, so you are better off asking arounds to see who has them. Also, if you go to
    the Saint John's Street Cycle website (http://www.sjscycles.com/store/vIndex.ht), they have tons of
    cranksets that they sell very cheap. They sell all kinds of really cool shit. They sell new and used
    cranksets, pieces of cranksets, like right crank alone, etc. They are british, so they name things
    differently. So you have to figure out what they mean by chainset and stuff like that. I am sure
    you'll find what you need in their website. Good luck,

    I just checked their website and they have an adaptor. Go to the 74 bolt circle chainwheels, and
    they have the adaptor at the bottom. they call it avid microadaptor.

    Andres

    Subject: Re: Is this gear combination allowed?
    >From: Sheldon Brown [email protected] Date: 6/14/2003 9:29 PM Mountain Daylight Time
    >Message-id: <[email protected]>
    >
    >Telford wrote:
    >> My touring bike currently has=20
    >>=20
    >> 26-36-46 RSX crank 12-32 shimano "P' 8 sp. cass Deore LX rear derail RSX front derail RSX STI
    >> Shifters
    >>=20 20
    >> Can I put a 22 ring on the smaller one (I need to put little lower gear for loaded touring but
    >> short of changing the whole crank to something like Deore 22-32-46, may be I can just change only
    >> the small chain ring??
    >>=20
    >> I know there's ring-difference that is not allowed, just not sure how it will be for me.
    >
    >Your crank uses the 74 mm bolt circle diameter (BCD). This means that=20 the smallest chainring
    >physically possible to fit it is 24 teeth.
    >
    >There would be no problem at all going to a 24, but 22 isn't possible=20 unless you replace
    >the crank.
    >
    >Sheldon "Limits" Brown
     
  5. Telford wrote:
    >>
    >>>My touring bike currently has=20 26-36-46 RSX crank

    >>>Can I put a 22 ring on the smaller one

    I replied:

    >>Your crank uses the 74 mm bolt circle diameter (BCD). This means that=20 the smallest chainring
    >>physically possible to fit it is 24 teeth.
    >>
    >>There would be no problem at all going to a 24, but 22 isn't possible=20 unless you replace
    >>the crank.

    AndresMuro top-posted:

    > There is something called a spider. It is an attachemnt that you use to reduce the bolt circle
    > from 74 to 58?? This will allow you to put a 20 or 22 teeth chainring.

    > I just checked their [SJS] website and they have an adaptor. Go to the 74 bolt circle
    > chainwheels, and they have the adaptor at the bottom. they call it avid microadaptor.

    The Avid Microdaptor was a wonderful thing, but has, alas, been extinct for several years. I'd be
    surprised if St. John's Street actually has any left.

    In any case, this won't help Telford, 'cause he's got a Shimano crankset. Older 110/74 cranks had
    the 110 section flush with the arms, and you would use 3 mm spacer washers betwixt the granny ring
    and the spider. The Avid Microdaptor is designed to replace these spacers.

    Shimano cranksets, however, have protrusions built into the arm spider, rather than using the spacer
    washers. This is generally a good thing, makes it easier to assemble, and provides a greater thread
    depth. Unfortunately, however, it precludes the use of the Avid Microdaptor even if one could locate
    one. If you tried to install one, there would be a huge chasm between the inner and middle
    chainrings, and the chain would fall between them.

    Sheldon "Nice Try Though" Brown +------------------------------------------------+
    | Man will occasionally stumble over the truth, | but most of the time he will pick himself up |
    | and continue on. -- Sir Winston Churchill |
    +------------------------------------------------+ Harris Cyclery, West Newton, Massachusetts Phone
    617-244-9772 FAX 617-244-1041 http://harriscyclery.com Hard-to-find parts shipped Worldwide
    http://captainbike.com http://sheldonbrown.com
     
  6. The extra long cage for the LX (GS, I think Shimano calls it) has a total capacity of 22 teeth.

    To figure the capacity you'll need, add the number of teeth on the largest chainwheel/cog
    combination THAT YOU USE, and then do the same for the smallest/smallest.

    Now subtract the smaller sum from the larger. This is the total tooth difference you'll need in
    your derailer.

    May you have the wind at your back. And a really low gear for the hills! Chris

    Chris'Z Corner "The Website for the Common Bicyclist": http://www.geocities.com/czcorner
     
  7. Matt O'Toole

    Matt O'Toole Guest

    "AndresMuro" <[email protected]> wrote in message
    news:[email protected]...

    > I used to have a Deore DX crankset and I put an adaptor on it and it worked fine. I do remember
    > that the spacers were kind of wide. I remember that I had to use some shorter bolts and no
    > spacers, or maybe thinner spacers, or, the adaptor backwards, or something like that. I do
    > remember that I ended up
    using
    > the longer bolts and the wider spacers on the big chainring and the bolts weren't flushed.It
    > wasn't difficult to figure out.I just tried different
    setups
    > until it looked functional. I used the crankset with this combination for several years with no
    > problems. I sold the crankset but kept the adapter. However, since I moved, I put it in a box and
    > I am too lazy to dig it out.

    IIRC, I had similar hassles with my DX crank -- trying to find the right combination of bolts and
    spacers. I was convinced at the time this was a conspiracy to get me to buy only official Shimano
    replacement parts. Different replacement chainrings required different thickness shim washers, and
    finding the right one was a real PITA. This is even worse with modern, sculpted chainrings, which
    are difficult to measure to the tooth centerline, so it's all trial and error. After taking the
    crank off and putting it back on 5-6 times, I'm ready to hurl a chainring at a Shimano product
    manager, for ninja-star target practice.

    Anyway, the Microdaptor did work. I don't remember how much fiddling it took, specifically.

    > Still if he doesn't want to try the adaptor, he can probably by a compact
    right
    > crankarm from SJS for about the same price.

    Probably. These days you can often get a whole new crank with 3 chainrings for less than what one
    Shimano chainring costs. Then all you have to worry about is if your BB is the right length... ;-)

    Matt O.
     
  8. On Sun, 15 Jun 2003 14:32:55 -0400 (EDT), [email protected] (Chris Zacho "The Wheelman") wrote:

    >To figure the capacity you'll need, add the number of teeth on the largest chainwheel/cog
    >combination THAT YOU USE, and then do the same for the smallest/smallest.

    Yeah, except use the largest/largest combination that you might ever shift into by mistake, or in
    other words, the largest/largest combination you *have*. You can't have the chain shorter than
    necessary for that or, eventually, Really Bad Things *will* happen.

    Jasper
     
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