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  1. #1
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    Chainline question when changing cranks.

    I am installing a Sugino 46/36/26 triple crank on an older used road bike with a seven speed cassette. Is it important to have the same chainline at the crank(distance from the bike centerline to the middle chain ring) as at the rear middle cassette gear ring by choosing the proper bottom bracket? In my case by selecting the correct spindle length? Also is there an ideal front derailer for this Sugino crank? My vintage Shimano setup has a crank(48,38,28) chainline of 49 mm and a rear mid cassette chainline of 41 mm and appears to work OK with most gear combinations. The Sugino with the original BB is 56 mm at the crank versus 41 mm at the rear, which appears very extreme by eye. The bike also has vintage Shimano STI indexed thumb shifters. I'm also hoping to achieve indexed shifting with the Sugino crank. I'm a newbie at this so please bear with me.

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    Yes, the proper spindle length is important. Usually, there are only two sizes of bottom bracket axles, one for double and one for triple...

  3. #3
    Senior Member sydney's Avatar
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    Quote Originally Posted by stonooka
    I am installing a Sugino 46/36/26 triple crank on an older used road bike with a seven speed cassette. Is it important to have the same chainline at the crank(distance from the bike centerline to the middle chain ring) as at the rear middle cassette gear ring by choosing the proper bottom bracket? In my case by selecting the correct spindle length? Also is there an ideal front derailer for this Sugino crank? My vintage Shimano setup has a crank(48,38,28) chainline of 49 mm and a rear mid cassette chainline of 41 mm and appears to work OK with most gear combinations. The Sugino with the original BB is 56 mm at the crank versus 41 mm at the rear, which appears very extreme by eye. The bike also has vintage Shimano STI indexed thumb shifters. I'm also hoping to achieve indexed shifting with the Sugino crank. I'm a newbie at this so please bear with me.
    BB spindle length match to crank being used is important.Current sugino 46/36/26 triples use a 113 or 118 spindle, the longer one with fatter seattubes or 135 dropout spacing. Thumb shifters werent sti,and the front was friction. How you approach indexing the front depends on the type of shifter you use. Road sti front sifter will require a road FD wich will work with the given rings. Mtb shifter will require a mtb FD that will handle the 46 big ring.

  4. #4
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    Thanks for the informative response. The original drive train is labeled Shimano 200CX. The 200CX is on both front and rear derailers, the Shimano triple crank and on the the thumbshifters. There is also a STI label on both thumb shifters. The front derailer definately indexes with the original setup. My rear dropout spacing is 130 mm. I believe I have ordered the correct length spindle from Harris Cyclery, which still lists about seven different ball and socket Sugino spindles.

    The bike is a Bianchi Adventure Cross, lug framed steel bike (made in Taiwan) with a slant top tube and 700C 36 spoke wheels. I purchased the bike used in good riding condition. I am not sure the drive train is original since the front top mount derailer interferes with using the seat tube water bottle holder brazes.


    The bike is equiped with a neat vintage Sakae drop bar and Sakae stem for a threaded fork, which would not be original for a cross bike. The nearby LBS label is still on the seat tube. I might drop in and try to get the original info on the bike.

  5. #5
    Senior Member sydney's Avatar
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    Quote Originally Posted by stonooka
    Thanks for the informative response. The original drive train is labeled Shimano 200CX. The 200CX is on both front and rear derailers, the Shimano triple crank and on the the thumbshifters. There is also a STI label on both thumb shifters. The front derailer definately indexes with the original setup. My rear dropout spacing is 130 mm. I believe I have ordered the correct length spindle from Harris Cyclery, which still lists about seven different ball and socket Sugino spindles.

    The bike is a Bianchi Adventure Cross, lug framed steel bike (made in Taiwan) with a slant top tube and 700C 36 spoke wheels. I purchased the bike used in good riding condition. I am not sure the drive train is original since the front top mount derailer interferes with using the seat tube water bottle holder brazes.


    The bike is equiped with a neat vintage Sakae drop bar and Sakae stem for a threaded fork, which would not be original for a cross bike. The nearby LBS label is still on the seat tube. I might drop in and try to get the original info on the bike.
    7 speed, STI thumbshifters(SIS maybe??), and old road bike(or even cross bike) is alot of stuff that does not compute.I've got some Shimano 400cx stuff that came off a a mid 90s(?) trek 7600 hybrid that used grip shifters and flat bar.

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    Thanks again. When I receive the spindle to match the Sugino crank, I will post the results. I anticipate having to replace the front der and perhaps loss of front indexing. If I am happy with the results with the new crank, I might replace the thumb shifters with Sora brifters. You can probably tell I'm a hardware junkie.

  7. #7
    Senior Member sydney's Avatar
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    Quote Originally Posted by stonooka
    Thanks again. When I receive the spindle to match the Sugino crank, I will post the results. I anticipate having to replace the front der and perhaps loss of front indexing. If I am happy with the results with the new crank, I might replace the thumb shifters with Sora brifters. You can probably tell I'm a hardware junkie.
    Ah Ha! I dug up a pair of dual lever 'thumb' shifters with the STI label on them, and yes the front is index and it's mountain bikey stuff, so you will need a mtb FD with them. 'Thumb' shifters are usually thought of as the single lever type sitting above the bar with no indexing in the front one.

  8. #8
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    Thanks Sydney,

    Yes, they are dual lever per shifter; one lever for down shifting and the other lever for upshifting. Thanks for continuing the research. Is the cable travel per shifter fixed or is there a hidden adjustment somewhere? What is the difference between a mtb front der and a road der? The front der on this bike is bottom cable pull. I thought most mtb front ders were top pull to avoid damage from the rough trail terrain conditions beneath the BB.

  9. #9
    Senior Member sydney's Avatar
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    Quote Originally Posted by stonooka
    Thanks Sydney,

    Yes, they are dual lever per shifter; one lever for down shifting and the other lever for upshifting. Thanks for continuing the research. Is the cable travel per shifter fixed or is there a hidden adjustment somewhere? What is the difference between a mtb front der and a road der? The front der on this bike is bottom cable pull. I thought most mtb front ders were top pull to avoid damage from the rough trail terrain conditions beneath the BB.
    There is no pull adjusrment. mtb FD can be top or bottom pull. Road FD are bottom pull.

  10. #10
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    Hi Sydney or anyone else who is interested,

    I received the 113 mm spindle for the Sugino 46/36/26 chain ring last week and finally got around to assembling it today. The 113 spindle does not work on my bike because the adjustment cup has wrenching protrusions on the outside surface which interferes with the left crank by a millimeter or so.
    The 117.5 mm spindle will not have the left crank interference but the chainring will be outboard by 1 1/2 mm more than with the shorter spindle. The chainline with either the 113 or 117.5 spindle is much improved over the original setup. The left crank will also be outboard more with the 117.5 but this is inconsequential, I think. The left crank was outboard a bunch with the original setup.

    I was pleasantly suprised to find the BB area on this old bike is clean.. no rust. The caged balls and the original bearing surfaces on the old spindle are in excellent condition and the lube was relatively clean. It looks like bike was not used very hard and stored out of the weather.

    It looks by eyeballing the chainline, that the old Shimano 200 SX FD will index with the 113 spindle and should index with the 117.5 if it is outboard by only 1 1/2 mm (.060 inches) more.

    I will check out one of my favorite used bike shop to see if I can find an adustment cup with no protrusions that uses a pinned spanner tool. If I am lucky to find a cup, I will also have to find a used tool or make or buy a new one. If not, I will have to exchange the 113 for a 117.5. Could not find such a cup on the WWW.

    After all this messing around, I could have probably used a sealed cartridge from the LBJ at the same cost,
    but I prefer to preserve the original ball and cup setup just to be different.

    Would appreciate any comments.

    Sinchi

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