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  1. #1
    Senior Member masi61's Avatar
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    Sora front triple index difficulties with 30-44-48 crank

    So I'm setting up this really cool women's specific 1883 Cannondale touring triple with interesting, rare ERTO 590 wheels and tires. A worthy project we thought. Everything is great and the bike is just about out the door with Sora 3 x 7 triple seven speed sti brifters. 7 speed rear s.i.s thread on freewheel with Shimano Light Action s.i.s. rear derailleur - a snap - the stuff works beautiful with the new Taya turbo chain. Triple front crank has 94 bcd chainrings in a 30-44-48 sorta halfstep with granny, sorta commuterbike mild gearing. Old friction front derailleur was a SunTour cyclone endless band. I decided to try a Shimano Deore (interestingly it also has Shimano's version of endless band). I went to the bikeshop and got a little nylon spacer for the front derailleur band to bring a 35mm down to a 31.8 mm to match the Cannondale seat-tube. The Deore front derailleur is engraved on the back of the cage "half-step" - interesting - I'm thinking - if anything has a shot of indexing on the first (or second, or third, or fourth ) try, this could be my ticket to precision.
    So I set the thing up...I must add that I'm a downtube shifter kind of mechanic, a little too old school I guess. Anyway, setting up the Sora Shifters was much easier than I thought.
    The problem is the grinding in the middle chainring mainly,only a few rear cogs are immune. The Sora shifts into 3 positions with very positive CLUNKs (as opposed to the rear where its satiny smooth light action quietness). I'm bidding on some 105 triple 31.8 FD's on ebay right now but I keep losing the auctions.
    Can anyway direct me on how to get this funky half step triple crank to index better with the Sora brifter ? Thanks.

  2. #2
    me have long head tube TallRider's Avatar
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    I think your problem is with the front derailler's cable-pull ratio more than with the chainring sizing. Main issue is that you're using a Shimano off-road front derailler with a road-triple indexed front shifter. As I understand it, Shimano's road-triple front deraillers have a different cable-pull ratio than Shimano's off-road front deraillers. So you'd need a 105 or Sora or Tiagra (etc.) triple-compatible front derailler.
    When you're shifting with a double-chainring setup with STI shifters, you can usually get away with whatever front derailler you want. Triples are much more finnicky and usually you'll need a Shimano front derailler designed for triple-STI shifting.

  3. #3
    Senior Member masi61's Avatar
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    Thanks for your prompt reply. I was kind of wondering if the cable pull was wrong due to it being a mtb front derailleur. They have a Tiagra 31.8 triple for $34.99 in stock at the LBS down the street and I can get 10% off that - still a little more than I wanted to pay but, OH Well - so maybe I'll go get it today. My friend who is bankrolling the project told me she wants it to work VERY WELL and she said she'll pay me a little more (50 bucks or less she said) for me to just get it dialed in right.
    The only concern I have with the Shimano 9 speed road triples is something I read on the specification sheet for the FD-5503,FD-5504 105 triple front derailleur. It reads: "Min. distance between top and intermediate - 10T".
    Now since the crank I'm using only has a 4T difference, can I still dial this thing in?
    Thanks again Tim for the quick response .

  4. #4
    me have long head tube TallRider's Avatar
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    Quote Originally Posted by masi61
    The only concern I have with the Shimano 9 speed road triples is something I read on the specification sheet for the FD-5503,FD-5504 105 triple front derailleur. It reads: "Min. distance between top and intermediate - 10T".
    Now since the crank I'm using only has a 4T difference, can I still dial this thing in?
    Thanks again Tim for the quick response .
    I doubt that difference will be a big problem, but it may be. I'd have set it up as a 48/40/30t myself. But the 44 may be the ideal cruising gear...

  5. #5
    Senior Member masi61's Avatar
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    I think you're right. Something like a 39, 40 or 42 would be better I think to make the thing a little more versatile. The only 94 bcd chainrings I find on ebay right now are like 44's (which is already on there) or like 32's.

  6. #6
    me have long head tube TallRider's Avatar
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    On the other hand, lots of older touring bikes with triple cranks had 52/48/30 chainrings, the idea being that the middle chainring was what you'd use most of the time and the granny was a bailout gear. I still don't think it's a great setup, but the 48/44/30 is kinda similar so it does have precedent.

    I'd not realized how difficult it's getting to find 94mm bcd 5-bolt chainrings. It might be easier/cheaper to get a used old MTB setup with 110mm bolt pattern and 46/36/26 chainrings.

  7. #7
    Senior Member Retro Grouch's Avatar
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    Quote Originally Posted by timcupery
    On the other hand, lots of older touring bikes with triple cranks had 52/48/30 chainrings, the idea being that the middle chainring was what you'd use most of the time and the granny was a bailout gear. I still don't think it's a great setup, but the 48/44/30 is kinda similar so it does have precedent.
    Yeah, but back in those days front derailleurs didn't have that deep inner blade like modern triple front derailleurs do. I think that the issue with the 10t minimum difference is that the inner blade might rub the middle chainring.

  8. #8
    Senior Member masi61's Avatar
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    That's partly what I was thinking, thus the attempt at making the Deore FD work. I fiddled and fiddled with the Deore this morning and there are a lot of issues but there is a sweet spot where you can get into a lot of gears without much rubbing. I'm going to ask my friend to try out the Deore FD and see if she can live with it.

  9. #9
    me have long head tube TallRider's Avatar
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    This is an example of why I really prefer Campy's non-indexed 13-increment approach to front shifting with brifters. Allows you to trim the front derailler cage and not worry about compatibility issues.

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