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  1. #1
    Senior Member Monster Pete's Avatar
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    Half-step plus granny conversion questions

    I have a 10-speed (2x5) bike from the early '90s I've been tinkering with, and was thinking of doing a HS+G conversion. It currently has 38-48 chainrings and a 14-17-20-24-28 freewheel. I was thinking of switching to a half-step setup, using 44t middle and 48t outer chainrings, with a 24t granny gear on the inside.

    Am I likely to run into any problems with this? I would set the chainline of the middle/outer chainrings as if they were a double, allowing me to use the 48/28 combo as part of the half-step setup. This would mean only really using using the 28-20 freewheel gears with the 24t chainring (24/17 would be borderline acceptable) but that places the granny gears in a neat sequence off the lower end of the half-step anyway. I'm thinking it's possible I'll run into problems getting the FD working correctly with such a big jump from small to middle chainring. Would it be better to ditch the granny gear and just go for a double?

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  2. #2
    coprolite fietsbob's Avatar
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    I bought a Specialized Expedition touring bike in the 80's , it came with a 48/44 triple.
    Would it be better to ditch the granny gear and just go for a double?
    28. is a 16t drop, 30 is a 14T drop, either pretty reasonable ,
    as if you have a smaller difference you gain only 1 0r 2 lower ratios
    making the added chainring more questionable benefit ,
    Vs a 14-32 5 0r 6 speed freewheel.

    then a granny gear seems less a gain..

    need a shallow back plate FD to clear the bigger middle ring.

    big jump between chainrings, is handled well at the summit of hills ,
    when the pull of force on the chain can be the least.
    Last edited by fietsbob; 09-14-11 at 09:39 AM.

  3. #3
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    I'm a big fan of the half step + granny, or similar configurations. They work fine allowing you to chose rings and a freewheel best suited to 99% of riding conditions, with a bailout for those long or steep grades that you run into occasionally. To make this work, you'll need to use a mountain or road triple FD, and possibly a long cage FD (maybe not if you only use the granny with larger sprockets) but other than that you'll be fine.
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  4. #4
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    Quote Originally Posted by FBinNY View Post
    I'm a big fan of the half step + granny, or similar configurations. They work fine allowing you to chose rings and a freewheel best suited to 99% of riding conditions, with a bailout for those long or steep grades that you run into occasionally. To make this work, you'll need to use a mountain or road triple FD, and possibly a long cage FD (maybe not if you only use the granny with larger sprockets) but other than that you'll be fine.
    I used to be a fan of half-step +granny back when 5 and 6-speed freewheels were the norm. Mine was a 46/42/26 triple crank and a 13x28 6-speed freewheel and the gear progression was very even with almost no duplicates. The OP is dealing with a very old type of gear arrangement and the hs+g is the only way to get even gearing steps plus an adequately low gear.

    Modern 9 and 10-speed cassettes have made half-step moot since the cog spacing is one tooth intervals for a lot of the range.

  5. #5
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    Quote Originally Posted by HillRider View Post


    Modern 9 and 10-speed cassettes have made half-step moot since the cog spacing is one tooth intervals for a lot of the range.
    Good point, with the steps so fine of 9s+, half step chainrings don't make as much sense. I've adjusted to step-and-a-half spacing, packing a nice assortment of very closed spaced ratios into the mid-upper range.
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  6. #6
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    Quote Originally Posted by FBinNY View Post
    Good point, with the steps so fine of 9s+, half step chainrings don't make as much sense. I've adjusted to step-and-a-half spacing, packing a nice assortment of very closed spaced ratios into the mid-upper range.
    In theory you could make half-step gearing with 9+ speed cassettes but the chainring spacing would be so close as to be useless. From a 12 to a 13T or a 13 to a 14T cog is about an 8% change. You would have to use something like 50/48T chainrings to get the 4% difference needed to "split" these.

  7. #7
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    I run half-step on a 7sp. freehub. The back is 11,13,16,19,23,28, and 34. On the front I have a 44-40 with a 20t grandpa gear. Of the 21 speeds there are 18 different usable gears.

  8. #8
    Senior Member oldbobcat's Avatar
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    Quote Originally Posted by fietsbob View Post
    need a shallow back plate FD to clear the bigger middle ring.
    What front derailleur do you recommend for this? In my experience all contemporary triple derailleurs, road and MTB, have a minimum gap from middle to outer of 10-12 teeth.

  9. #9
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    Quote Originally Posted by davidad View Post
    I run half-step on a 7sp. freehub. The back is 11,13,16,19,23,28, and 34. On the front I have a 44-40 with a 20t grandpa gear. Of the 21 speeds there are 18 different usable gears.
    I can see why this works since your cassette has such a wide range the steps between adjacent cogs are quite big. It's analogous to a 5 speed 14x28 or a 6-speed 13x28 freewheel.

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