Vintage 650B build- GT Tachyon- Mtbr.com
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  1. #1
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    Vintage 650B build- GT Tachyon

    I usually post over in the Vintage forum, but I thought you guys might like my new bike. I just finished this- it's a 1991 GT Tachyon. Originally came with 700D wheels (GT called it a "crossover bike"). When I learned that the difference in diameters between 700D and 650B was minimal, I started looking for rims, tires, and tubes. I built it up with same-year 1991 Shimano XT bits, for the most part. Are there any other 700D bikes out there? They are great candidates for 650B wheels.

    IMG_1066.jpg

    IMG_1067.jpg

    And here's what it looked like in 1991:

    IMG_1167.jpg

  2. #2
    Mr.650b - Mr.27-5
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    Great looking bike! What size is it?

    I worked for a GT dealership and had one of these back in the day. It was a great bike for the era even though knobby were hard to come by for them.

    Have fun with it and give us a full ride report after you've gotten some good off road miles on her.

    Cheers,

    KP
    www.bikelugs.com

  3. #3
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    Quote Originally Posted by Kirk Pacenti
    Great looking bike! What size is it?

    I worked for a GT dealership and had one of these back in the day. It was a great bike for the era even though knobby were hard to come by for them.

    Have fun with it and give us a full ride report after you've gotten some good off road miles on her.

    Cheers,

    KP
    www.bikelugs.com
    Thanks man! I'll definitely post some after-ride remarks, and photos too. I'm sure you've heard it before, but thanks for the tires. They're awesome, and I can't wait to get 'em dirty. The frame is a 18", c-t-c.

  4. #4
    Mr.650b - Mr.27-5
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    Quote Originally Posted by djmuff
    Thanks man! I'll definitely post some after-ride remarks, and photos too. I'm sure you've heard it before, but thanks for the tires. They're awesome, and I can't wait to get 'em dirty. The frame is a 18", c-t-c.

    If you ever want to sell her.... let me know!

  5. #5
    Doesntplaywellwithmorons!
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    Only GT used the 700D size, and they invented it. Why they didn't just adopt 650B instead
    (when they had to go to IRC to have a run of tires made anyway) has always been a
    source of wonder since the difference in bead diameter is 3mm (the 700D being 3mm
    larger). I saw the model below the tachyon listed on the local craigslist a few months ago
    but didn't buy it. It was a cross-terrain model called the Continuum, 72/73.5 angles on a
    plain gauge tange infinity chromoly frame. The tachyon was listed in the mountain bike
    model line, had the same angles but used a double-butted tubeset.
    I don't post to generate business for myself or make like I'm better than sliced bread

  6. #6
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    Got the tires dirty yesterday, and it was great fun. Really smooth, I noticed the difference in the bigger wheels, even if they are only 1" bigger. Tires were great. I'm running Sun CR18's with lightweight tubes, and was happy to not get a flat.

    IMG_1176rs.jpg

  7. #7
    Mr.650b - Mr.27-5
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    Nice!

    There really is something beautiful about the simplicity of MTB's from this era!

  8. #8
    TNC
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    djmuff...how'd you like the way the Neo's fit those CR18 rims?

  9. #9
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    I remember those bikes...I actually thought of them when I first learned of the 650B idea.
    (My brother is riding around on a vintage GT Karakoram w/ the under the chainstay U-brake.)

    Anyway, it would be interesting to play around with the adjust able off-set fork to see what works best with the wheel size.

  10. #10
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    Quote Originally Posted by TNC
    djmuff...how'd you like the way the Neo's fit those CR18 rims?

    They were tight. It wasn't impossible mounting them, but I definitely needed a strong tire lever to get the last of the bead up and over the rim. And I'm not excited about having to change a tube. I feel it will be a pain removing a tire- more of a pain than mounting one.

  11. #11
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    I want one of these purely bacause of the U-Brake....

  12. #12
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    The horz. drop outs on the fork are amazing. Great looking bike.

  13. #13
    Mr.650b - Mr.27-5
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    I still want to buy this bike!

    cheers,

    KP

  14. #14
    Harshing my mellow, man..
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    We just built up one of these bad boys that we had sitting in the back of our shop. I'll post the pictures as soon as I load them up.

  15. #15
    Harshing my mellow, man..
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    As promised..

    Well, I got bored and I'll be posting the pictures sooner than I had expected. These have been taken with my phone, so the quality might not be as good as wanted.
    Attached Images Attached Images

  16. #16
    TNC
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    Hey Baylor...you're famous now. Baylor works at the same shop that I do, and I wondered how long it would take him to post up his frankenbike. He's even running that setup in tubeless form now. He was out at the trail this evening with that thing when I went for my ride. That thing has been sitting in the back storeroom at the shop for awhile. Only Baylor wanted to bring it back from the dead.

  17. #17
    YESBRO!!!
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    <a href="https://www.flickr.com/photos/datenschwanz/3141166817/" title="GT Tachyon Cross bike by datenschwanz, on Flickr"><img src="https://farm4.static.flickr.com/3118/3141166817_00f563b022_o.jpg" width="1920" height="1080" alt="GT Tachyon Cross bike" /></a>
    <a href="https://www.flickr.com/photos/datenschwanz/3141996610/" title="flip-flop stem by datenschwanz, on Flickr"><img src="https://farm4.static.flickr.com/3221/3141996610_7c80e22b8f_b.jpg" width="1024" height="576" alt="flip-flop stem" /></a>
    <a href="https://www.flickr.com/photos/datenschwanz/3141995290/" title="suntour accu-shifter shifters by datenschwanz, on Flickr"><img src="https://farm4.static.flickr.com/3097/3141995290_79db88ccb2_b.jpg" width="1024" height="576" alt="suntour accu-shifter shifters" /></a>

  18. #18
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    here are some pictures of my '91 Tachyon





    locobaylor, how did the pacenti tires fit the 700D rims?

  19. #19
    Mr.650b - Mr.27-5
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    Quote Originally Posted by Valen
    here are some pictures of my '91 Tachyon





    locobaylor, how did the pacenti tires fit the 700D rims?

    That thing is near mint! Let me know if you ever want to sell her.

    Cheers,

    KP

    PS: Word is my tires will go on a 700d rim, but you'd never want to try to fix a flat on the trail. Getting them off will be much harder than getting them on.

  20. #20
    Harshing my mellow, man..
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    Quote Originally Posted by Valen
    here are some pictures of my '91 Tachyon


    locobaylor, how did the pacenti tires fit the 700D rims?
    Just as Kirk said, they fit very snug, to be kind. I run tubeless, so I don't have to worry about them falling off on the trail. But it wouldn't be very fun to change a flat on the trail, like Kirk said again.
    Kirk, check your PM's please.

  21. #21
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    Quote Originally Posted by Kirk Pacenti
    That thing is near mint! Let me know if you ever want to sell her.

    Cheers,

    KP
    Hi!

    Yes it is in a good condition, but it's not mint. There are some stains and scratches, I had to change the bottom bracket (now a TA SpecialitÚs) and the chain (now Rohloff SLT99). I also replaced the original Suntour XC Ltd rear derailleur with a new XCE one.
    I really thought of selling her, and I tried it here in Germany a few weeks ago. But now with the opportunity of getting rims and tires that will fit in the frame, I'm thinking it over. Maybe I'll just ride it...
    I'll let you know, when I'm selling it...

    Here are some more photos: http://fotos.mtb-news.de/user/view/33876/page:1

    Cheers Uwe

  22. #22

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    I'll apologize in advance for semi-hijacking the thread, but I am trying to reach owners of the Tachyon.

    Does anyone still have the original crank/rings from their Tachyon to either sell or trade? I have an older Tachyon version without the threadless stem, ajustable fork, and with different ring sizes. My crank is a Suntour XC-LTD with 46-36-24 rings. I would love to get the rings described in the ad listed above in the 52-42-32 flavor.

    TIA

  23. #23
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    Quote Originally Posted by Gault
    I'll apologize in advance for semi-hijacking the thread, but I am trying to reach owners of the Tachyon.

    Does anyone still have the original crank/rings from their Tachyon to either sell or trade? I have an older Tachyon version without the threadless stem, ajustable fork, and with different ring sizes. My crank is a Suntour XC-LTD with 46-36-24 rings. I would love to get the rings described in the ad listed above in the 52-42-32 flavor.

    TIA
    Gault,
    I have the set that you're looking for, just send me a PM or email and I'll try to work something out with you. Thanks.

  24. #24

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    locobaylor,

    TY. I sent you a PM, I cannot send you an e-mail through the forum, it is blocked.

  25. #25
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    It's cool to see this thread get some more attention. I'm still riding my Tachyon, and I love it. I bought a Peace 9er a few months ago, and now I have two big-wheel GTs.
    I love them both, but the Tachyon is just soo cool. Here's pics of both.

    IMG_1173rs.jpg

    IMG_1627.JPG

  26. #26

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    Here's my Tachyon. I intend on doing more road riding, but I live in an area where the roads are a bit rough, so I want the thicker road tires the Tachyon offers. That and I live in Colorado, so I plan on riding some serious hills and the three front rings might help there.

    This tachyon is a bit different, it doesn't have the adjustable front fork or the threadless stem.

    Hey, locobaylor, let me know if you are still willing to sell the bigger rings.


  27. #27
    Drinking the Slick_Juice
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    that gt would make a fine SS
    "If women don't find handsome , they should at least find you handy."-Red Green

  28. #28

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    I will claim ignorance, SS= Single speed?

    If so, why would you say that? I am always willing to be educated.

  29. #29
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    Quote Originally Posted by Gault
    Here's my Tachyon. I intend on doing more road riding, but I live in an area where the roads are a bit rough, so I want the thicker road tires the Tachyon offers. That and I live in Colorado, so I plan on riding some serious hills and the three front rings might help there.

    This tachyon is a bit different, it doesn't have the adjustable front fork or the threadless stem.

    Hey, locobaylor, let me know if you are still willing to sell the bigger rings.

    Wow, I've never seen a blue Tachyon, nor one that big!?! What year and size is that?

  30. #30

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    I am not sure about the year, I bought it used. How would I determine that?

    It is 22", just about perfect for me and my use for road riding.

  31. #31
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    I just got in some 700D rims and knobbie tires. Anxious to build them up, but I have no bike to put them on.....

  32. #32
    Witty McWitterson
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    where'd you find 700D rims?
    Just a regular guy.

  33. #33
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    NEW 700D tires

    I have access to brand new 700D knobbies if anyone is interested. they are NOS shipped by GT, I think they are manufactured by IRC but i might be wrong.

  34. #34
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    Quote Originally Posted by ~martini~
    where'd you find 700D rims?
    700dpalace.com , duh.


    Yes I would be interested in IRC 700D knobbies!

  35. #35
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    Quote Originally Posted by harvestlaser
    I have access to brand new 700D knobbies if anyone is interested. they are NOS shipped by GT, I think they are manufactured by IRC but i might be wrong.
    Me too!
    Just my brother and I just purchased a Tachyon off eBay and would love to get some new rubber for future use.

  36. #36
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    new 700D knobbies spam

    I have posted the tires on ebay.
    Title: 700D Mountain Bike TIRES fit GT tachyon NOS NR 700 D
    Item number: 140301183582
    good luck

  37. #37
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    Holy thread jack batman.

    I guess this has become the Tachyon Info thread.

  38. #38
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    Hello everyone I have been riding this bike on the road for quite a while but now it's time to get new tires which is impossible. I've noticed some people are doing the 650b thing. My question is do i need new rims? Or will my original 700D rims work with these tires? Thanks a lot!

  39. #39
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    Scroll up and read POST#19

  40. #40
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    Just to let anyone and everyone know I just threw on some 650B Fatty Rumkins and those suckers work great! I'm going a bit more road riding but if i gotta hit some rougher roads or trails then it's still a good ride.

  41. #41
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    My Tachyon is a low miles (~250) all original parts 1991 model. Still has the 700D rims and I have been hoarding the tires for a couple years.... have 1.4slicks, 1.4 connecting ridge knobbies and 2.0 knobbies. I recently grabbed a pair of Araya RM17 NOS rims as well. I also have a Quatrefoil Tandem from the same year with 700D's.

    So will the Pacenti 650B tire fit on the 700D rim? DJ your's looks great with those monster knobbies!
    Attached Images Attached Images
    Needed: 26.8mm XTR seatpost, blue GT/Grundig Jersey.

  42. #42
    Mr.650b - Mr.27-5
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    Quote Originally Posted by gm1230126
    My Tachyon is a low miles (~250) all original parts 1991 model. Still has the 700D rims and I have been hoarding the tires for a couple years.... have 1.4slicks, 1.4 connecting ridge knobbies and 2.0 knobbies. I recently grabbed a pair of Araya RM17 NOS rims as well. I also have a Quatrefoil Tandem from the same year with 700D's.

    So will the Pacenti 650B tire fit on the 700D rim? DJ your's looks great with those monster knobbies!

    I want these bikes!

    Cheers,

    KP

  43. #43
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    Quote Originally Posted by Kirk Pacenti
    I want these bikes!

    Cheers,

    KP
    Howa manies dos yas wants?
    Needed: 26.8mm XTR seatpost, blue GT/Grundig Jersey.

  44. #44
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    If you can find one....the neat and rare model to own is the GT Virage which was a 7005 aluminum frame model with 700D wheels and a mix of Shimano's 400CX and 700CX cross groups. From what I remember it twas available in Silver or Blue and if I remember right it was the 1990 model year Virage. I bought one for my dad who piled over 50K in commuting miles on it. Two summers ago he began battling Parkinson's and locked it up somewhere and could not remember where. MAJOR loss.
    Needed: 26.8mm XTR seatpost, blue GT/Grundig Jersey.

  45. #45
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    Quote Originally Posted by DeeEight
    Only GT used the 700D size, and they invented it. Why they didn't just adopt 650B instead
    (when they had to go to IRC to have a run of tires made anyway) has always been a
    source of wonder since the difference in bead diameter is 3mm (the 700D being 3mm
    larger). I saw the model below the tachyon listed on the local craigslist a few months ago
    but didn't buy it. It was a cross-terrain model called the Continuum, 72/73.5 angles on a
    plain gauge tange infinity chromoly frame. The tachyon was listed in the mountain bike
    model line, had the same angles but used a double-butted tubeset.
    The last batch of 700D tires produced were actually light skinwalls made by Cheng Shin in 1999 before the Schwinn/GT bankruptcy and the white label on the side of the tire actually says Schwinn.
    I have a couple pair of those. IRC's still got the mold but they either wanted a 2500 or 5000 minimum order the last time in inquired and I couldn't afford to do it.
    Needed: 26.8mm XTR seatpost, blue GT/Grundig Jersey.

  46. #46
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    I remember someone bringing one of those tandems into my shop in Lincoln, Nebraska, looking for a new rim, or possibly just a tire. That was in 2001 I think. We were baffled from the 700D size and I specifically remember the Sutherlands book gettting brought out for further investigation....

  47. #47

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    I hope I'm not speaking out of place here, don't want to hijack when I just joined, but along the lines of the 700d, I just picked up a Quatrefoil Tandem, and have had a Tachyon (identical to Datenschwanz, what year is that?) in the garage missing wheels for ~5 years. The tandem, luckily, came with an extra set of wheels, BONUS! I almost converted the bike to a flat bar road bike, I'm glad the wheels didn't line up with the brakes, or I would have never known what it was!

    I'll have pics of them up as they progress, here's the only one i have thus far of the Quatrefoil.



    BTw, gm1230126: You have PM.

  48. #48
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    I have a 91 Quatrefoil that I was planning on doing a major update with disc brakes and 650b wheels. But just to see, I tried the 650b tires on the 700d wheels and they fit fine. Not any tighter than some tire I've dealt with in the past that were nominally the same size. So for now, I'll be riding it stock with the 650b tires. Still planning on doing the up date later when time and money allow. I'm just glad I can keep it ridable for now.
    Need: McMahon brake for roller cam mounts, Mountain Goat fork.

  49. #49
    Doesntplaywellwithmorons!
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    If anything, the 3mm larger bead seat diameter of the 700D should make for a tighter fit with a Neo-Moto when you do the thing tubeless. Its essentially the same effect as building up the bead area with tape/rubber rimstrips.
    I don't post to generate business for myself or make like I'm better than sliced bread

  50. #50
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    Quote Originally Posted by gm1230126
    If you can find one....the neat and rare model to own is the GT Virage which was a 7005 aluminum frame model with 700D wheels and a mix of Shimano's 400CX and 700CX cross groups. From what I remember it twas available in Silver or Blue and if I remember right it was the 1990 model year Virage. I bought one for my dad who piled over 50K in commuting miles on it. Two summers ago he began battling Parkinson's and locked it up somewhere and could not remember where. MAJOR loss.
    I know where there is a practically new Virage with many XTR bits and drop bars.

    Back in '97, we thought it was a dork bike...and we were right.

  51. #51
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    Paging all Quatrefoil Owners!!

    Hey all you 700d tandemers, I just picked one up and have a few questions..

    First of all, how is the rear clearance with the 2.35 Neo=Moto, decent or scant?

    Also, what size(s) seatpost does your tandem take. Mine came with two posts (obviously) but I assumed they'd be the same diameter. My captain's post is a 29.4, the stoker's is a 29.2. Did someone replace a post with the nearest size the LBS had in stock, or is this the way they're supposed to be?

    Thanks.

    Plum
    This post is in 3B, three beers and it looks good eh!

  52. #52
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    Are the posts matching style/type? Where did you find the Tandem and what size is yours? I think both of my posts 29.2 but I will check.
    Needed: 26.8mm XTR seatpost, blue GT/Grundig Jersey.

  53. #53
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    Quote Originally Posted by gm1230126
    Are the posts matching style/type? Where did you find the Tandem and what size is yours? I think both of my posts 29.2 but I will check.
    No, my 29.2 post is a Sakae TCO, the 29.4 is a Kalloy generic, which I suspect is a replacement post and was the closest the LBS could come up with.

    I found the bike through the local craigslist, complete, but not original. All the Deore timing/drive set is there, the front and rear DX derailleurs, etc, but the saddles, one of the posts (evidently) and the captains stem had been swapped out at one time. I have the 700d wheels and 1.4" tires, but they're dry rotting and need to be replaced. I think it's a 19/17, but I have not measured to confirm.

    I'm looking to do the 650b conversion, but I want to be able to fit a 2.35 in there for some cushion, I'm hoping that someone has tried it or can do a test fit for me before I start buying new equipment.

    Plum

    Edit, measured the frame as a 20/18 with a 22" TT length for the captain. With a short TT length like that, it might be suitable for a drop bar setup.
    Last edited by Plum; 12-13-2009 at 08:45 PM.
    This post is in 3B, three beers and it looks good eh!

  54. #54
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    Quote Originally Posted by gm1230126
    Are the posts matching style/type? Where did you find the Tandem and what size is yours? I think both of my posts 29.2 but I will check.
    Hey gm, just wondering if you'd had a chance to peek on your seatpost sizes yet?

    Thanks.

    Plum
    This post is in 3B, three beers and it looks good eh!

  55. #55
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    Plum mine's got 29.4 front and rear. Brrrr cold night here for checking that out
    Needed: 26.8mm XTR seatpost, blue GT/Grundig Jersey.

  56. #56
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    Mine are also 29.4 front and rear. Posts are original to the bike and are GT labeled and Kalloy made. The 2.3 Neomotos fit fine. The closest place to hitting the frame is on the inside of the drive side chain stay but theres still about 3/16 clearance. I don't have the rear u-brake on it at the moment, but I remember it bein a little close through the brake but not too bad as long as its not excessively muddy.
    Need: McMahon brake for roller cam mounts, Mountain Goat fork.

  57. #57
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    Quote Originally Posted by gm1230126
    Plum mine's got 29.4 front and rear. Brrrr cold night here for checking that out
    Thanks for checking that, I guess the Sakae TCO was the replacement post then.

    Plum
    This post is in 3B, three beers and it looks good eh!

  58. #58
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    Quote Originally Posted by muddybuddy
    Mine are also 29.4 front and rear. Posts are original to the bike and are GT labeled and Kalloy made. The 2.3 Neomotos fit fine. The closest place to hitting the frame is on the inside of the drive side chain stay but theres still about 3/16 clearance. I don't have the rear u-brake on it at the moment, but I remember it bein a little close through the brake but not too bad as long as its not excessively muddy.
    Double confirmation that 29.4 is the right size, thanks man. Even better, thanks for confirming the Neo-Moto fit. What rims are you running them on? I'm leaning towards the new P-35's..

    Plum
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  59. #59
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    Mine are still on the original 700D Araya RM20 rims. Fit like a glove.
    Last edited by muddybuddy; 12-17-2009 at 11:43 AM.
    Need: McMahon brake for roller cam mounts, Mountain Goat fork.

  60. #60
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    Muddybuddy and Plum what model year are your tandems. Mine has original GT/True Temper logo'd chromoly posts.
    Needed: 26.8mm XTR seatpost, blue GT/Grundig Jersey.

  61. #61
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    Quote Originally Posted by gm1230126
    Muddybuddy and Plum what model year are your tandems. Mine has original GT/True Temper logo'd chromoly posts.
    Best I can tell, my tandem is a '91. DX front and rear derailleurs, 1st gen XT triggers (push/pull, not push/push), LX level u-brake and cantilever up front, Deore timing and drive chain sets, exage hubs.

    Bummer is that my original stem went missing an owner or two ago, I have a 1 1/8" quill Hsun Ling high rise stem instead.

    I have the original wheels, exage hubs on the araya rims, with the 1.4" tires. As above, my one or both of my original posts have gone missing, I suspect the generic (non rebranded) kalloy is the original and that the Sakae TCO is a replacement.

    While we're on the subject, what are the options for stoker stems on these bikes? Can I use the control tech stoker stem with a 29.8mm clamp, does it close tight on the 29.4 post? Stick with the original stoker setup?

    Plum

    PS, I forgot to mention, my paint is black, no irridescent colors in my paint, only in the 'Quatrefoil' decals..
    This post is in 3B, three beers and it looks good eh!

  62. #62
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    Mine is also a '91 as pictured here in Dakarti White.

    http://www.mtb-kataloge.de/Bikekatal...GT1991_USA.pdf
    Need: McMahon brake for roller cam mounts, Mountain Goat fork.

  63. #63
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    Am I glad to read this thread!!!!! I have aquired(sis-inlaws) gt tachyon with 700d wheels and am worried about getting a flat cause I haven't got any spares at all...tyres,tubes etc. No one has these sizes over here in aus...or are as rare as hens teeth so can anyone send me some links for online shops where I can get some tyres to fit or 650b rims and tyres to convert. The bike will be used for road riding so slicks or semi slicks are the way I want to go.

    Its a great looking bike that has had minimal use when first bought back in about 1990 and has been garaged and unused for most of its life. Still on the original tyres too.

    looking forward to any info
    sneezy1

  64. #64
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    Google a few of these and you'll find plenty of sources where you can pick them up.

    Street/road:
    Panaracer Col De La Vie 650B x 38
    Panaracer Fatty Rumpkin 650B x 40mm

    Wider/trail:
    Pacenti Neo Moto 2.3"
    Pacenti Neo Moto 2.1"
    Pacenti Quasi Moto 2.0"
    Schwalbe Racing Ralph 2.2"
    IRD/Pana Fire XC Pro 2.1"
    Kenda Nevegal 2.3"
    Kenda Nevegal 2.1"
    WTB Wolverine 2.2"
    Needed: 26.8mm XTR seatpost, blue GT/Grundig Jersey.

  65. #65
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    Pacenti's new ParisMoto is a 650x38 and should be what you're looking for in a road tire. You can order them off his bikelugs.com website.

  66. #66
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    Thanks heaps guys! Just to double check before I order....the Panaracer Col De La Vie 650B x 38 or Pacenti's new ParisMoto is a 650x38 both would fit ok on my araya RM20 rims?

    I'm looking forward to doing a bit more riding on this bike if I can get it sorted.

    Thanks again
    sneezy1

  67. #67
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    I'm currently running 2.3 Pacenti Neo Motos on my GT tandem with the original 700d rm20 rims. They fit perfectly.
    Need: McMahon brake for roller cam mounts, Mountain Goat fork.

  68. #68
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    Thanks muddybuddy. It's good to know that the bikes not rubbish after all!! I'll be getting some of the slicks tho and possibly doing a tubeless conversion as well. In the searches I have done since yesterday, I have only found 650b tubes that are presta valved. I assume you can get them with schrader valves?

    regards
    sneezy1

  69. #69
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    Quote Originally Posted by sneezy1
    Thanks muddybuddy. It's good to know that the bikes not rubbish after all!! I'll be getting some of the slicks tho and possibly doing a tubeless conversion as well. In the searches I have done since yesterday, I have only found 650b tubes that are presta valved. I assume you can get them with schrader valves?

    regards
    sneezy1

    26" tubes fit fine--just stretch them a little. (if you can't find 650b tubes)

    The PariMoto won't be available for another month or so but should be pretty fast and light. The CLDV is surprisingly good for the money--I just commuted to work on a set half an hour ago!

    Also look at the Grand Bois options...I don't know if they're available on your continent tho--maybe Vintage Bicycle Quarterly will ship? Worth a check:

    http://www.vintagebicyclepress.com/tireoffer.html

  70. #70
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    You could always get the presta adapter if you can't find shrader.

    BTW, I find this thread very dangerous as I now want to go out and find one of these bikes. I feel like it's the predecessor to a Rawland.....which is also on my wish list......and that list is too long according to my wife. Bikes are awesome.

  71. #71
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    Quote Originally Posted by SteveF
    26" tubes fit fine--just stretch them a little. (if you can't find 650b tubes)

    The PariMoto won't be available for another month or so but should be pretty fast and light. The CLDV is surprisingly good for the money--I just commuted to work on a set half an hour ago!

    Also look at the Grand Bois options...I don't know if they're available on your continent tho--maybe Vintage Bicycle Quarterly will ship? Worth a check:

    http://www.vintagebicyclepress.com/tireoffer.html

    Thanks for that. I did look at the Grand Bois option. For the price locally I can get 4 cldv + tubes sent from the US.....so I've just ordered some..

  72. #72
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    Quote Originally Posted by sneezy1
    Thanks for that. I did look at the Grand Bois option. For the price locally I can get 4 cldv + tubes sent from the US.....so I've just ordered some..

    Yeah, the Grand Bois aren't exactly a budget-conscious option...

  73. #73
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    Quote Originally Posted by SteveF
    26" tubes fit fine--just stretch them a little. (if you can't find 650b tubes)

    The PariMoto won't be available for another month or so but should be pretty fast and light. The CLDV is surprisingly good for the money--I just commuted to work on a set half an hour ago!

    Also look at the Grand Bois options...I don't know if they're available on your continent tho--maybe Vintage Bicycle Quarterly will ship? Worth a check:

    http://www.vintagebicyclepress.com/tireoffer.html

    I got myself a set of CLDV's and have put them on but......what pressure do you run yours at? I'm at 50psi at the moment and they don't quite saet properly on the bead. Guess I'm a bit gutless to go too much further and run the risk of bursting one of my new tubes! The weather here has turned a bit sh#t too so haven't ventured out on any bike for a few weeks...

    thanks for your help
    sneezy

  74. #74
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    Barring any sentimental attachment value to a Tachyon what are they worth complete? Wasn't there one on ebay a month ago?

    I'm trying to wage the cost vs the probability of having to replace wheels/tires with new.

  75. #75
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    Quote Originally Posted by bme107
    Barring any sentimental attachment value to a Tachyon what are they worth complete? Wasn't there one on ebay a month ago?

    I'm trying to wage the cost vs the probability of having to replace wheels/tires with new.
    Unless the wheels are shot, there's no need to replace, 650b tires fit fine. I have mine mounted up with some Neo-Moto 2.35s.

    I paid $300 for a 700d tandem (Quatrefoil) last fall, I'd wager a tachyon in good condition would be anywhere from $100 to $300, depending on the parts, with $300 being showroom condition.

    Plum
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  76. #76
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    GT tachyon tires

    I recently came across some NOS GT crossover tires 700d X 2.0 if any one has any interest.
    [email protected]

  77. #77
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    another GT crossover Tachyon

    Hi and pleased to find other vintage crossover Tachyonites. I've had mine for some years but my 700D tyres are through to the canvas, however thanks to this and other mtbr 'tachyon' threads, I have just ordered a set of KP 650B tyres to see how hard they are to get on the original rims? Otherwise I suppose I will have to look into a new 650B wheelset.

  78. #78
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    Quote Originally Posted by liefbike
    Hi and pleased to find other vintage crossover Tachyonites. I've had mine for some years but my 700D tyres are through to the canvas, however thanks to this and other mtbr 'tachyon' threads, I have just ordered a set of KP 650B tyres to see how hard they are to get on the original rims? Otherwise I suppose I will have to look into a new 650B wheelset.
    Mine mounted up without tools easily. Bead seated without issue, seems the sizing is a perfect match for the 650 tires I've tried (schwalbe's from rivendell and Neo-Motos).

    Plum
    This post is in 3B, three beers and it looks good eh!

  79. #79
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    Thanks - waiting on the arrival of the Neo-Motos and I will let you know how they fit onto the RM 20 rims. On another GT crossover issue, I have looked at the 1991 catalogue and notice that some models came with flat bars and in that year at least the Tachyon came standard with drop bars. In my case however, for some reason, my Tachyon has a flat bar ? Having never ridden off road with drop bars, I wonder what difference they would make ?

  80. #80
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    ps being quoted about A$400 -$500 for new 650B wheels using Velocity rims or similar

  81. #81
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    Drop bars are pretty awesome off road. Normally you would use a shorter stem with more rise with drop bars. Off road drop bars have more flare than the ones that came on the Tachyon though, and you usually ride in the drops almost all the time. The classic off road drop bars came from WTB/Nitto, but their new ones aren't the same. Similar bars are On One Midges, Salsa Woodchippers, and others. Lots more discussion of drop bars offroad in the Vintage, Retro, and Classic forum. Here is a pic of some WTBs on a Potts

    <a href="https://smg.photobucket.com/albums/v651/datawhacker/potts/?action=view&amp;current=0250.jpg" target="_blank"><img src="https://img.photobucket.com/albums/v651/datawhacker/potts/0250.jpg" border="0" alt="Photobucket"></a>

  82. #82
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    drop bars are much kinder on wrists than flat or even riser bars. YMMV though w/ drop bars i feel like i have better reflexes cause i am more "inside" the bike than on top.. hard to describe the ergonomics but it's way different.
    WTB: Bomber Z2 1 1/8 steerer, in good to excellent shape OR bomber rebuild kit.

  83. #83
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    Thanks for the replies - I will see what's around in these bars.

  84. #84
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    tachyon

    I gather that the 2.3 neo motos will go onto the original RM 20 rims, however can they also then fit with the original brakeset, front and back ?

  85. #85
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    They'll fit both the RM-20 and RM-17 700D versions.
    Needed: 26.8mm XTR seatpost, blue GT/Grundig Jersey.

  86. #86
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    tachyon

    Did either require much alteration of the brakes

  87. #87
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    The difference in rim diameter is well within the adjustment range of the brakes.
    Need: McMahon brake for roller cam mounts, Mountain Goat fork.

  88. #88
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    Brake clearance was OK and so was front end, however a bit tight at the back as per photo. I think someone else has 'trimmed' the knobs, but that seems a bit rough on the Neo Motos


  89. #89
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    Quote Originally Posted by liefbike
    Brake clearance was OK and so was front end, however a bit tight at the back as per photo. I think someone else has 'trimmed' the knobs, but that seems a bit rough on the Neo Motos
    That is pretty tight. I picked up a Tachyon recently and put 2.3" Nevegals on it and have more clearance than what you have. Are you sure that's a Tachyon? I didn't think that they came in teal (it looks more like the color of an Arette).
    Each bicycle owned exponentially increases the probability that none is working correctly.

  90. #90
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    No doubt about it's being a tachyon - see photo

    I have now spent another A$100 to try a Neo Moto 2.1 on the rear, which is I gather is 4 mm narrower at the tread, although I am hoping the scaled down profile will be narrower.


  91. #91
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    Weird. That doesn't have the adjustable front dropout either. There is one here also:

    http://www.flickr.com/photos/7556426...n/photostream/

  92. #92
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    Well they were after all available two years...imagine that. One year they had the 2x4 fork and one they didn't
    Needed: 26.8mm XTR seatpost, blue GT/Grundig Jersey.

  93. #93
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    The 2.1 just fits, so now to try my new drop bars and (unfortunately) in stuffing around with the wider Neo Moto I have damaged the rear derailleur. As I do not want to pay more than $100 for a similar Suntour XCD, another should suffice.


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  95. #95
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    Quote Originally Posted by gm1230126
    Well they were after all available two years...imagine that. One year they had the 2x4 fork and one they didn't
    Was the Tachyon also offered in 1990? Both the '91 and '92 had the adjustable front fork (at least per the catalogs). The '91 was purple (not sure if there were any alternate colors) and the '92 was Midnight Aura.

    The decals confirm that it's a Tachyon, but it doesn't seem to match up otherwise. Very odd.
    Each bicycle owned exponentially increases the probability that none is working correctly.

  96. #96
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    For reference this is the clearance that my '91 frame has with brand new 2.3" Nevegals.
    Attached Thumbnails Attached Thumbnails Vintage 650B build- GT Tachyon-20110513120858.jpg  

    Each bicycle owned exponentially increases the probability that none is working correctly.

  97. #97
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    Another oddity is that this bike has a flat bar, when the catalogue has it with drops ?

    I bought the bike in the mid 1990's from what I assumed was the original owner and if that was so, I suppose he might have ditched the original set of drops ?

    I seem to recall that flat bars were gaining in popularity, especially for those who bought this kind of bike for their daily ride.

    On the other hand GT may have varied the model configuration here in Australia, although that does not make a lot of sense, given the catalogue.

    I haven't looked for a serial number, but that would be the logical way to date the bike.

  98. #98
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    and the bike's groupset, wheels etc. are the same as other original Tachyons

  99. #99
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    Quote Originally Posted by djmuff
    I feel it will be a pain removing a tire- more of a pain than mounting one.
    I think you got that right. I'd go ahead and slime them, if it was me; You may end up removing them with tinsnips.

  100. #100
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    mine is probably more late 80's and hasn't got the adjustable front drpouts and happens to be that teal/blue-ish colour.
    I have worn out the cassette and need a new one.....anybody know where I can source one from either the US or from Aus??? It's the standard 7 speed although I haven't counted the teeth yet to get the exact range.....but I'll be doing some hill work so I guess 13x26 or so would be close...

    Thanks for any help.
    sneezy


    edit.....just went out to the garage and counted teeth....the old one is 13x30.
    Last edited by sneezy1; 12-16-2011 at 01:29 AM.

  101. #101
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    I managed to find one on ebay from the US, which cost me about $100 - unfortunately the seller only had one, however the description id ''NOS Suntour Accushift Plus 7-Speed Cassette...13x30''.

  102. #102
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    oh and I forgot to say I have two 650B x 23 Neo-Motos for sale if anyone wants them

  103. #103
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    Quote Originally Posted by liefbike View Post
    I managed to find one on ebay from the US, which cost me about $100 - unfortunately the seller only had one, however the description id ''NOS Suntour Accushift Plus 7-Speed Cassette...13x30''.
    OK thanks...I did a search and found a couple..a 13x24 and a 13x26....my rear derailleur is an old suntour XCD....is that compatable with accushift?? It seems throwing in that one word has me scared lol....it either get that one for $140 aus dollars or look at a complete 650 wheel and cassette...and this is all on a bike that is borrowed. 140 bucks is more than a 10th of a new bike.....

    thanks for the info
    sneezy

  104. #104
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    Bumping an old thread: I was just given one of these bikes by the local Re-Cycle shop where I do a lot of parts buying.

    Afraid the system won't allow me to post the direct links - yet. Trust me, the pics are horrible. Take a normally hipster abused bike, then give it an "I don't care" rattlecan green paint job without removing any of the components. Other than the crank, which is missing.

    Obviously, I've got one hell of a challenge ahead of me. I'm probably going to rebuild the wheels 650A, as the bike is going to be primarily used on pavement with some playing on the trails on my property. Tires are limited, although I've found Sunlites that'll work just fine for the limited dirt road/mild trail riding I'll put it thru. And then do a set of 650B wheels later. Yes, that is a VERY bad rattlecan job, sprayed over the original paint and decals, and onto some of the components. I'll take a short shot at rubbing off the green, but will probably end up having the frame powdercoated in a matching magenta.


    Doubt if I'll have this on the road before summer, given the other restoration jobs I've already got lined up in the shop. Just the same, I'm intrigued by the bike considering I'm way more of a roadie than a mountain biker.

    Syke
    Montpelier, VA

  105. #105
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    Congrats on the pickup Syke! Bummer about the green paint, but I'm glad you are at least going to try to strip it. I had a pink Klein that someone had spray painted black, and I was able to strip the black off over the course of two days. Hopefully you can rescue that original magenta- it might look good under there, especially if the decals are still present.

    Please keep us posted on your progress. It's great to see all the love for the original GT Tachyons. This thread just keeps going....

  106. #106
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    Quote Originally Posted by djmuff View Post
    Congrats on the pickup Syke! Bummer about the green paint, but I'm glad you are at least going to try to strip it. I had a pink Klein that someone had spray painted black, and I was able to strip the black off over the course of two days. Hopefully you can rescue that original magenta- it might look good under there, especially if the decals are still present.

    Please keep us posted on your progress. It's great to see all the love for the original GT Tachyons. This thread just keeps going....
    Did a bit of messing with the bike (I'm currently working on four other projects for sale at the Westminster, MD swap meet on 12 Feb), added a rear derailleur, seat, seatpost and crankset out of inventory. The immediate game plan is to put on some 650B tyres and a chain on the bike and try riding it. See if I actually like the bike before proceeding.

    Definitely will try to remove the green, but I'll admit I'm not getting my hopes too high. I've been spoiled by having a really good and not terribly expensive powder coater in my area, and I know he'll have no problem matching the magenta. That is in the future, however.

    First I've got to make some money at Westminster.

    As to the condition of the bike, I'm finally active enough to put a few pictures up:





    Last edited by sykerocker; 01-25-2012 at 05:02 PM.

  107. #107
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    so , where exactly is this swap meet in westminster , md ?

  108. #108
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    Quote Originally Posted by motorbykemike View Post
    so , where exactly is this swap meet in westminster , md ?
    Good question. I'd also like to know since I'm a little less than 1 hours drive away in Ellicott City, Maryland.

  109. #109
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    Quote Originally Posted by Ratman View Post
    Good question. I'd also like to know since I'm a little less than 1 hours drive away in Ellicott City, Maryland.
    The county agricultural complex in Westminster. Go to STOP, SWAP AND SAVE for the full details. Very worthwhile attending, preferred budget of about $500 is recommended. You'd be amazed at what can be found there. Equal road and mtb attendance - also can be very interesting if you're interested in old non-suspension bikes.

    I'll be set up with my buddy Kirk O'Brien in the dealer area - nothing too special this year, just a bunch of $125.00 road 10-speeds that I've rebuilt (the core of my work, selling to college students) and a few framesets. Just ask for Syke and introduce yourself. If you're looking at the 2011 setup, the space is marked O'Brien/Paczolt, space #137. We expect to be in about the same place this year.

  110. #110
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    bump

    Howdy folks, I just got my hands on a magentaishpurple Tachyon (same as the bike in the o.p.). I plan on building it up 650b monstercross style but the problem is that the previous owner converted it to 700c with a hybrid fork and a file to the u-brake. Obviously I'll have to change the fork to run 650b, does anyone know what the A-C measurement of the original fork is?

  111. #111
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    repeat bump

    Well, as of this morning it's on the road:







    My next task is to get clear pictures of all the decals in the hopes I can get someone to make me a set. I still need to find the proper crank (the Sugino is just to get it running for the moment), and the rear derailleur is a SunTour XC slightly below the original equipment. Otherwise, I'm going to be doing a lot of riding.
    Syke
    Montpelier, VA

    I own a mile of trails. Guess I'm a mountain biker.

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    Wow! Syke, that looks great! And it looks like you were able to strip the green. Well done!

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  114. #114
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    That looks awesome! Care to share details on how you went about stripping it?

  115. #115
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    Quote Originally Posted by djmuff View Post
    Wow! Syke, that looks great! And it looks like you were able to strip the green. Well done!
    Afraid not. It took me a day just to clean half the top tube, and I discovered that the paint underneath was just as bad as a rattlecan green. That's powdercoat. I managed to find a shade that matched the original color exactly. Cost a bit, since that's a two layer coat (metallic silver underneath), but I'm really happy with the final result. And damn, it rides nice. I've got no problem keeping up with my buddies on straight out road bikes.
    Syke
    Montpelier, VA

    I own a mile of trails. Guess I'm a mountain biker.

  116. #116
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    Darn, I was hoping you were going to share some mysterious home brew stripper that pulled off the green paint and decals leaving just the glorious magenta behind Great looking bike, can't wait to get mine rolling.

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    EJ, if you still have the original fork it would be nice to keep it on the bike. I'm going to PM you regarding your fork.

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    This is awesome man!!

  119. #119
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    Quote Originally Posted by Cracked Headtube View Post
    EJ, if you still have the original fork it would be nice to keep it on the bike. I'm going to PM you regarding your fork.
    Appreciate the offer as I'd almost kill for the original fork, would love to play around with adjustable trail. The previous owner had got the frame from a buddy in the GT warranty dept., the fork had been poached off of it. The p.o. was running a fork from a 700 GT hybrid but the rear u-brake couldn't quite hit a 700c wheel correctly. Got to love shop rat frankenbikes

    I picked up a 1" disc brake fork with a 399 a-c measurement, the hybrid fork measured 405ish fwiw. Fingers crossed that this lands me somewhere in the originals variable spec.

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    The Tachyon lives again in its new guise !


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    " width="549">

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    " width="549">

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    My contribution to this thread

    I have been following this thread for sometime now. It's nice to see these rare bikes come back to life. I myself have a few of them and use them as much as I can. I have the Quatrefoil, Tachyon and Continuum. I don't have a pic of the tandem but here are the other two.

    Tachyon


    Continuum


    Currently running on original 700d tires but soon will get the 650B's squeezed onto the original rims.

  125. #125
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    They look great - are they the original color, mine isn't.

    I could not get excited about the original teal, so this is the result after a sand blast, hours of hand rubbing and then a powder coat. The color is a very slight gloss b'bque black.

    I tried unsuccessfully to buy some Soma B-line 650B tires for better surfaces but ended up ordering 650B Panaracer Col de la Vie tires from Jensen. What are you running and are they original 700D or 650B ?

  126. #126
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    Sorry missed the reference to your tires

  127. #127
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    Sorry missed the reference to your tires and I have had no probs getting the Pacenti tires to fit the slightly larger rims

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    Hi Liefbike,

    The color is original, they are black as far as I can tell. The Rims and Tires are the 700D size. I have on the Tachyon the slick ones, the Continuum now has the big knobbies, and the Quatrefoil has the small knobbies. I also have an extra sets of 700D tires in both big and small knobbies, but I may switch all the tires out because I worry about the tires failing due to rot.

    When I order tires, they will be Schwalbe Marathon. But I'm going to hold out for a bit if I can on that.

    I want to do the Quill/Stem Adapter and change the stem out to one more comfortable for my 2 bikes.

    I like your dirt drop bars, I plan on doing that to my Continuum soon, but worry about the shifters placement. Do you have pics on how yours are setup?

    Thanks for posting, I like how yours looks.

  129. #129
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    Great Find!

    I picked one of these up last night at a thrift store for $40
    Looks just like this > Vintage 650B build- GT Tachyon-img_2837-1024x768.jpg

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    Khepra congrats... Now where are them pics?

  131. #131
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    Quote Originally Posted by zwordz View Post
    Khepra congrats... Now where are them pics?
    Coming!!

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    Hi everyone please allow me to introduce myself my name is Joe Barr I own a bicycle shop in Phila, and I got hold of one of those 1991 Tachyon that is all original with the 700 d wheels didn't realize how difficult is to get tires

  133. #133
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    Hi Joe,

    It is tough but you can squeeze 650B tires onto that rim...

    So... where are the pics of your ride??? I have 3 700D wheel size bikes and like seeing how many others are out there...

    - Ben

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    Aaaaaaand three years later, updated pics! lol

    With mods.
    Vintage 650B build- GT Tachyon-img_20160712_200840.jpgVintage 650B build- GT Tachyon-img_20160712_200953.jpgVintage 650B build- GT Tachyon-img_20160712_201053.jpgVintage 650B build- GT Tachyon-img_20160712_201039.jpgVintage 650B build- GT Tachyon-img_20160712_201502.jpgVintage 650B build- GT Tachyon-img_20160712_201758.jpgVintage 650B build- GT Tachyon-img_20160712_201813.jpg

    Quote Originally Posted by Khepra View Post
    I picked one of these up last night at a thrift store for $40
    Looks just like this > Click image for larger version. 

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  135. #135
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    Thank God you finally updated, I've been sitting here refreshing the browser waiting for it.

    These are really cool bikes. Everything I like about that vintage of mountain bike and the tire sizes I'm liking these days.

  136. #136
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    Vintage 650B build- GT Tachyon-img_3735.jpgActually I've been thinking about whether to keep this bike, which I have now converted to a commuter. Accordingly I have relaced the knobby tires with 'panaracer col de la vie'. These 650B's will go on the rims, albeit with slightly more of an effort, given they are a bit smaller than the 700D rims.

  137. #137
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    Latest Pics + Mods!

    Quote Originally Posted by Khepra View Post
    I picked one of these up last night at a thrift store for $40
    Looks just like this > Click image for larger version. 

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ID:	836436
    Vintage 650B build- GT Tachyon-img_0736.jpgVintage 650B build- GT Tachyon-img_0738.jpgVintage 650B build- GT Tachyon-img_0739.jpgVintage 650B build- GT Tachyon-img_0743.jpgVintage 650B build- GT Tachyon-img_0745.jpgVintage 650B build- GT Tachyon-img_0747.jpgVintage 650B build- GT Tachyon-img_0748.jpgVintage 650B build- GT Tachyon-img_0750.jpgVintage 650B build- GT Tachyon-img_0751.jpgVintage 650B build- GT Tachyon-img_0753.jpgVintage 650B build- GT Tachyon-img_0756.jpgVintage 650B build- GT Tachyon-img_0759.jpg

  138. #138
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    LOL! Sorry

  139. #139
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    I recently picked up a purple GT Tachyon for a pretty good price. It was in rough shape but all original. The plan was a 650b conversion, but sadly, after riding it a bit I had to admit that it was just too small... Luckily I found it a good home with an employee at Recycled Cycles in Seattle. I know this is an old thread but, hey, I gotta post 10 times before I can put pictures up!

  140. #140
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    Quote Originally Posted by Ann87 View Post
    I recently picked up a purple GT Tachyon for a pretty good price. It was in rough shape but all original. The plan was a 650b conversion, but sadly, after riding it a bit I had to admit that it was just too small... Luckily I found it a good home with an employee at Recycled Cycles in Seattle. I know this is an old thread but, hey, I gotta post 10 times before I can put pictures up!
    congrats on your purchase, I loved that bike but alas I had to thin the herd out, and it was one that went fast... enjoy the bike and please post a pic... btw, I have some spare rims/tires avail... let me know.

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