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  1. #1
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    Seatpost diameter 1983 Trek MTB?

    I need to replace the seatpost on my original Trek but the place on the post the states the diameter is worn away. Does anyone know the diameter?

  2. #2
    Wrench Savant balindamood's Avatar
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    Is it an 830 or 850?? (not sure they had an 830 in '83)
    "Where you come from is gone;
    where you are headed weren't never there;
    and where you are ain't no good unless you can get away from it."

  3. #3
    cs1
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    Quote Originally Posted by balindamood View Post
    Is it an 830 or 850?? (not sure they had an 830 in '83)
    Not sure anybody except Specialized was making a factory bike in 1983. Trek sure wasn't.
    1999 Waterford RSE-11, 1995 Waterford 1200, 1989 Specialized Rockhopper Comp
    1989 Raleigh Technium, 1989 Schwinn Traveler, 1986 Specialized Rockhopper
    1984 Specialized Stumpjumper, 1986 Specialized Stumpjumper and just way too many projects to list.

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    a77impala a77impala's Avatar
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    I think '83 was Treks first year for Mtn bikes. I have an '85 870 and the seat tube is 27.2 mm. I have six Treks and all have the same size post.


    I just checked vintage-trek.com and the 850 was the first Mtn bike by Trek, in 1983. The only one in '83
    Last edited by a77impala; 02-01-11 at 10:37 AM. Reason: more info Trek mtn bikes
    Treks, 79-710, 83-500,600, 85-420, 87-560, 90-930, 91-1000, 92-1000, 93-930, 95-930, 96-930, 1220, LeMonds, 2000 Zurich, 05-Etape, 06-Versailles

  5. #5
    Old fart JohnDThompson's Avatar
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    Quote Originally Posted by cs1 View Post
    Not sure anybody except Specialized was making a factory bike in 1983. Trek sure wasn't.
    Yes, we were. The Trek model 850 was introduced in 1983, built with Reynolds 531AT tubing.

    OP's bike probably uses a 26.8mm post.


  6. #6
    Bianchi Goddess Bianchigirll's Avatar
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    doesn't the current seatpost have the size stamped on it somewhere?
    Last edited by Bianchigirll; 02-01-11 at 10:47 AM.
    Bianchis '87 Sport SX, '90 Proto (2), '91 Boarala 'cross, '93 Project 3, '88 Trofeo, '86 Volpe, '89 Axis, '79 Mixte, '99 Mega Pro XL Ti, '97 Ti Megatube, , '90 something Vento 603,

    Others but still loved,; '80 RIGI, '80 Batavus Professional, '87 Cornelo, '86 Bertoni (sold), '09 Motobecane SS, '98 Hetchins M.O., '09 K2 Mainframe, '89 Trek 2000, '?? Jane Doe (still on the drawing board), '90ish Haro Escape

  7. #7
    I'm Carbon Curious 531phile's Avatar
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    Call around and find a shop that has sizing poles(not sure what to call them) that they can insert into the seat tube to find out the exact seatpost size. You won't be able to eyeball the difference between 0.1 or 0.2mm when you line up seatpost. I tried lining up two seatpost because I had your same problem, turns out it was off by 0.4mm. It looked like they had the exact same diameter. It was only after I inserted the sizing poles that I learned I need a 26.8 vs. the 27.2 that I thought it needed.

    Don't take the chance by inserting one that is too small because it will mess up your seat tube, maybe even cause it to crack!!!

    See if you can find it on the vintage Trek website. Just google it. They have catalogs and a bunch of other info.
    Last edited by 531phile; 02-01-11 at 11:18 AM.

    Quote Originally Posted by avner View Post
    I loled. Twice. Then I cried. Then I rubbed one out and cried again, but thanks for sharing.

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    Senior Member LesterOfPuppets's Avatar
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    Here's the Mombat page on it. No seatpost diameter listed, however.

    They claim it's Tange Champion MTB tubing.

    Pic from Mombat:
    1980ish Free Spirit Sunbird fixed * 1996 Mongoose IBOC Zero-G * 1997 KHS Comp * 1990-ish Scapin * Olde Western Auto Cruiser.

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    Senior Member LesterOfPuppets's Avatar
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    Brochure at Vintage Trek says Tange also.

    Brochure says it's an SR MTE 100 post, but still no diameter listed.

    Crazy adjustability on that post!

    I'm starting to think John's 26.8 is a good guess, as that's the only size I've seen that post in so far.
    1980ish Free Spirit Sunbird fixed * 1996 Mongoose IBOC Zero-G * 1997 KHS Comp * 1990-ish Scapin * Olde Western Auto Cruiser.

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    Senior Member LesterOfPuppets's Avatar
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    Oops, velobase claims the post came in 26.6 - 27.2mm sizes.
    1980ish Free Spirit Sunbird fixed * 1996 Mongoose IBOC Zero-G * 1997 KHS Comp * 1990-ish Scapin * Olde Western Auto Cruiser.

  11. #11
    Old fart JohnDThompson's Avatar
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    Quote Originally Posted by LesterOfPuppets View Post
    They claim it's Tange Champion MTB tubing.
    The first run used Reynolds 531AT. Later runs used Tange MTB and eventually Tange Prestige tubing.

  12. #12
    Fuji Fan beech333's Avatar
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    Wouldn't any bike shop be able to measure. Hell, I had a Performance shop do it once.
    Seeking a 165mm Sugino Super Mighty track crankset.

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    Bianchi Goddess Bianchigirll's Avatar
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    Quote Originally Posted by 531phile View Post
    Call around and find a shop that has sizing poles(not sure what to call them) that they can insert into the seat tube to find out the exact seatpost size. You won't be able to eyeball the difference between 0.1 or 0.2mm when you line up seatpost. I tried lining up two seatpost because I had your same problem, turns out it was off by 0.4mm. It looked like they had the exact same diameter. It was only after I inserted the sizing poles that I learned I need a 26.8 vs. the 27.2 that I thought it needed.

    Don't take the chance by inserting one that is too small because it will mess up your seat tube, maybe even cause it to crack!!!

    See if you can find it on the vintage Trek website. Just google it. They have catalogs and a bunch of other info.
    Stien calles them "seatpost sizing rods" they are at the bottom of the page. http://www.jastein.com/Html/Tools_for_Frames_Forks.htm

    Quote Originally Posted by beech333 View Post
    Wouldn't any bike shop be able to measure. Hell, I had a Performance shop do it once.
    they should be able to it just depends on the person he runs into. I would not trust too many 'mechanics' these days to do.



    I ha thought these were made of a good polished stainless steel. the set I bought last year were alloy and I was a bit disappointed.
    Bianchis '87 Sport SX, '90 Proto (2), '91 Boarala 'cross, '93 Project 3, '88 Trofeo, '86 Volpe, '89 Axis, '79 Mixte, '99 Mega Pro XL Ti, '97 Ti Megatube, , '90 something Vento 603,

    Others but still loved,; '80 RIGI, '80 Batavus Professional, '87 Cornelo, '86 Bertoni (sold), '09 Motobecane SS, '98 Hetchins M.O., '09 K2 Mainframe, '89 Trek 2000, '?? Jane Doe (still on the drawing board), '90ish Haro Escape

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    wonder what the price was on that 850 in 83

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    Yes, it's the 850. 26.8 sounds good but thanks for the many suggestions to take it to the LBS and have it measured. Doy!

  16. #16
    a77impala a77impala's Avatar
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    I bought a cheap plastic vernier caliper to measure seat posts from Harbor Freight in Austin for just couple bucks, sure saves a lot of time
    trying to find the right post.
    Treks, 79-710, 83-500,600, 85-420, 87-560, 90-930, 91-1000, 92-1000, 93-930, 95-930, 96-930, 1220, LeMonds, 2000 Zurich, 05-Etape, 06-Versailles

  17. #17
    Senior Member spinbackle's Avatar
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    This is an '84/'85 850 and the seatpost size is 27.0. I have an '87 Stumpjumper Comp w/the same seatpost size. Awesome riding bike BTW.

    047..JPG052..JPG034..JPG037..JPG
    Last edited by spinbackle; 02-01-11 at 08:16 PM.
    '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

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