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  1. #1
    Senior Member spinbackle's Avatar
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    New Tandem Frame...Need Advice

    This is the first of what is probably going to be a lot of questions in the future as I'm putting together a new tandem from the frame up.

    My son finally outgrew the trail-a-bike (he's about to turn 8 and about 65 lbs.)

    I have the wheels, seatposts/seats, rear derailleur,V-brake calipers, and fork on the frame already. Cranks, BBs, front derailleur,stem, bars, and Ergo shifters are waiting to be put on.

    I have a stoker stem (adjustable) that is 29.8 diameter. Problem is my seatposts are 31.6. Before I start hunting on the internet, is there such a thing as a 31.6 stoker stem? No matter how much I try to spread the stem I cannot get the seatpost through it.

    I need to know how many chains to buy for the drive chain and for the timing chain.

    I also need to know a good brand of brake/derailleur housing to use and how many sets I need to buy (I've found extra long cables and travel adjusters already).

    Any help/advice would be appreciated.

    I built a half bike this way but this is not going quite as smoothly.

    Scott
    '84 Trek 850--spinbackle-built, '85 Trek 670 Campy Nuovo Record--project, '87 Trek 560 SS/Fixed--project, '87 Specialized Stumpjumper Comp w/ Deore XT--Specialized-built, '87 Rossin Record, '03 LeMond Wayzata--commuter,
    '?? TST Mtn Bike frame--project, '07 Tsunami Tandem--home-built

  2. #2
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    would you consider buying a new seatpoast that will fit the adjustable stoker stem?
    then all you need to do is get the right shim that will reduce 31.6 to the new seatpost diameter.
    Rommel and Lucille

  3. #3
    hors category TandemGeek's Avatar
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    What brand and model of tandem is this?

    Regardless, as already noted, consider using a smaller diameter seatpost with a shim: easy and inexpensive.

    Otherwise, if you're dealing with 1.25" seatposts and a stoker stem didn't come with the bike, you'll probably need to cobble one together using one of Santana's 1.25" alloy handlebar stems, which you can find at any of their better-stocked tandem speciality dealers, e.g., www.precisiontandems.com comes immediately to mind. I think they may offer one as long as 150mm. If that's not long enough you could either use any one of a variety of different styles of handlebars, flipped upside down and backwards and with or without an ASX-50 stem riser / adapter: again, something you'll find at the better tandem speciality dealers. There are some very pricey 31.6mm carbon stoker booms on the market, i.e., $250 from Stealth, etc... but you'd probably pay less for a custom steel stoker stem from someone like Bushnell Cycles, Bilenky, Bob Brown, or any local frame builder. As previously mentioned, the smaller seatpost for the captain with a shim is a far more practical solution.

    As for chains, it takes 1 standard 112 - 118 link chain for the drive side and ~1.5 for the timing side (depends on the length of the boom tube and the number of teeth on the timing ring), so a total of 3 chains should do it. Some better bike shops sell chain off a spool and they could provide you with a continuous length of chain for the timing chain for a few bucks less than two better quality standard length chains.

    One standard set of cable housings should be all you need. Housing is not normally used for the long cable runs between the cable stops at the front and back of the tandem. Some off-road tandems are the exception where a few short lengths of housing are sometimes needed at the top-tube and captain's seat tube junction.

  4. #4
    Senior Member spinbackle's Avatar
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    Quote Originally Posted by the desert fox View Post
    would you consider buying a new seatpoast that will fit the adjustable stoker stem?
    then all you need to do is get the right shim that will reduce 31.6 to the new seatpost diameter.
    Thanks for the help...I think a 27.7 seatpost with the appropriate shims will make my life a lot easier.

    Scott
    '84 Trek 850--spinbackle-built, '85 Trek 670 Campy Nuovo Record--project, '87 Trek 560 SS/Fixed--project, '87 Specialized Stumpjumper Comp w/ Deore XT--Specialized-built, '87 Rossin Record, '03 LeMond Wayzata--commuter,
    '?? TST Mtn Bike frame--project, '07 Tsunami Tandem--home-built

  5. #5
    Senior Member spinbackle's Avatar
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    Quote Originally Posted by TandemGeek View Post
    What brand and model of tandem is this?

    Regardless, as already noted, consider using a smaller diameter seatpost with a shim: easy and inexpensive.

    Otherwise, if you're dealing with 1.25" seatposts and a stoker stem didn't come with the bike, you'll probably need to cobble one together using one of Santana's 1.25" alloy handlebar stems, which you can find at any of their better-stocked tandem speciality dealers, e.g., www.precisiontandems.com comes immediately to mind. I think they may offer one as long as 150mm. If that's not long enough you could either use any one of a variety of different styles of handlebars, flipped upside down and backwards and with or without an ASX-50 stem riser / adapter: again, something you'll find at the better tandem speciality dealers. There are some very pricey 31.6mm carbon stoker booms on the market, i.e., $250 from Stealth, etc... but you'd probably pay less for a custom steel stoker stem from someone like Bushnell Cycles, Bilenky, Bob Brown, or any local frame builder. As previously mentioned, the smaller seatpost for the captain with a shim is a far more practical solution.

    As for chains, it takes 1 standard 112 - 118 link chain for the drive side and ~1.5 for the timing side (depends on the length of the boom tube and the number of teeth on the timing ring), so a total of 3 chains should do it. Some better bike shops sell chain off a spool and they could provide you with a continuous length of chain for the timing chain for a few bucks less than two better quality standard length chains.

    One standard set of cable housings should be all you need. Housing is not normally used for the long cable runs between the cable stops at the front and back of the tandem. Some off-road tandems are the exception where a few short lengths of housing are sometimes needed at the top-tube and captain's seat tube junction.
    Thanks for the help!

    The frame is an '07 Tsunami Road Tandem. Just a cheap way to see if my son (8 y.o.) and I will like tandeming.

    Here's what's going on it:

    Campy Ergo 10-speed shifters
    Avid Single Digit 7 V-brakes (frame and fork are disc ready if I choose to go that way...real flat here)
    Nashbar Carbon Cross fork
    Velocity Dyad Wheelset
    American Classic Cassette
    Campy Chorus Triple rear derailleur
    Campy Comp Triple front derailleur
    Truvativ Elita Triple Tandem crankset
    Truvativ ISIS BBs
    Wippermann 10 speed chain
    FSA headset
    ...and a few other odds and ends

    I've built a single from the ground up but this is taking a bit more time, and money.

    Looking at replacing the cranks/BBs some time in the future with Phil BBs and a square taper tandem crankset.

    Bars are Salsa and seatposts are Thomson.

    Scott
    '84 Trek 850--spinbackle-built, '85 Trek 670 Campy Nuovo Record--project, '87 Trek 560 SS/Fixed--project, '87 Specialized Stumpjumper Comp w/ Deore XT--Specialized-built, '87 Rossin Record, '03 LeMond Wayzata--commuter,
    '?? TST Mtn Bike frame--project, '07 Tsunami Tandem--home-built

  6. #6
    Senior Member
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    i hope you can post a blow by blow pix of the build.
    it would be fun building it as riding.
    Rommel and Lucille

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