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  1. #1
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    Optimum Deraileur Drivetrain

    For a deraileur equipped lightweight city bike with 650B X 42m Hetre tires, what would be an excellent shifting set up for a gear range of approximately 20-95 inches? I might be stuck using a V-O crankset, what would I be sacrificing compared to a Shimano crankset?

  2. #2
    coprolite fietsbob's Avatar
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    Which Shimano crankset? there have been many sorts..

    if you can get a TA Cyclotourist Crankset, they allow 2 chainrings of wide difference
    to be paired together.
    On a bike tour down the Cal coast my companion from Britain had a 50tooth ring and a 28 tooth ring.

    A hybrid drive train using schlumpf planetatry 2 speed crank is another approach
    his 2 overdrive cranks are 1.6X and 2.5X the size of the small chainring
    He also manufactures, in Switzerland, a reduction geared crank, I have one of those
    That I fitted on my Brompton Folding bike, to accompany its 3 speed hub..

    In my case the chain never leaves the chainrings on either end, as both ratio changes are internal..



    My 54 t ring is in effect a 21.6t granny .. the 50t ring size divided by 2.5 comes out an even 20t.

    on my 16" wheel bike.. low is 17" high is 77 " which is excellent for my purposes.


    In derailleur bikes triples with a 58 94 pairing , or a 74 110 bolt circle pairing will work too .

    in the 80's, attracted by shiny objects, i used a Campag triple as a double..
    Middle 52, inner 36, outer a cyclocross chainguard.
    it is 144, the inner an 86 mm , machined into the crank arms
    Gipiemme triple arms were thickened to suit.
    back then 13 t was as small as cogs on derailleur bikes were.
    Last edited by fietsbob; 12-31-10 at 10:47 AM.

  3. #3
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    too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
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    There's no one answer. You could go double or triple depending on your riding style and preferences. Glancing at this gear chart (which may be off a bit based on actual tire diameter) you can see that a 44/12 yields a decent high as would a 40 or 42/11. At the other end a 22/28, 24/30 or 26/32 would all give you the low you need.

    I prefer not to go above 28t on freewheels (just a preference, not saying it creates problems otherwise) and like tight gearing for use on the road, so I'd probably do something like a 12/28 cassette with a triple 22/34/44 crankset. I haven't worked it out in detail so that's something you need to do for yourself. For a mtn bike I'd probably opt for a double with a wider cassette, and use outer chainring position for a bashguard.

    You have lots of options, so use a gear chart to determine your endpoints then slot in the various choices for the middle based on available hardware.
    Last edited by FBinNY; 12-31-10 at 12:00 PM.
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    So far, I have never had success with using a double ring with a large gap of 20+ teeth for wide range gearing. I think a triple is the way to go unless somebody has a combination they know can work well. Chain suck on the downshift was a big problem with the dual chainring. I am unfamiliar with the latest equipment (I know all about TA!), so I don't know what to expect. What I need are recommendations for equipment groups that people know from experience will work. Price is not a major concern. I have heard the 650B wheel size could present some front deraileur clearance problems with mountain bike groups, it is this kind of stuff I need to know. Thanks for the help!

  5. #5
    coprolite fietsbob's Avatar
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    Another calculation .. more wheel sizes http://sheldonbrown.com/gears/

    On my touring bike which has 700c wheels 50/14 was a 95"
    24/34 or 32 was the low. 6 speed freewheel so 17 20 24 28 in between,


    a 40 or a 38.. campag race triple is a 24,40 50 dropping the 30..
    74 130 BCD lets the middle one be a 38

    optimum seems a Rohloff hub for Me, now
    down shifts when youre nackered to a stand still

  6. #6
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    A Rohloff hub is supposed to work well for this application. No experience with one and lots of people don't like the friction and noise on a road bike. I will try one soon, but I might be too old a dog for this new trick.

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