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Thread: Noodle-like XL frame problem

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    Default Noodle-like XL frame problem

    Hi everyone,

    Bit of background: I've been building for 4+ years, 26 frames so far, mtb, cx, rd, cargo, fat, etc. I started building because I needed a frame that would fit my 220mm cranks (I'm a Zinnonite and 6'8", 240 lbs). My CX and Mtn bikes have 38.1mm True Temper OX Platinum DTs, 31.8mm top tubes - oversize and thick to handle the huge torque of long cranks and a big rider. Both those frames work well for me. Because of the long cranks, the BB is quite high and therefore the ST is relatively short compared to the TT: 525mm c-t ST, 649mm ETT on my CX frame, 465mm c-t ST, 663mm ETT on my Mtn bike frame. I know, that's weird but, it works and it works well. (I don't really want anyone to get sidetracked with the long cranks and weird geo here. I've studied, researched and ridden a lot and it works very well for me)

    Last summer, I decided to do a little experiment and go with smaller diameter and thinner walled tubes for a road+ bike. You can see it here: Lyle's Road Plus Light Tourer | LTWiens This has similar geo to my CX frame however, the chainstays are longer, and the ST is 605mm instead of 525mm. I also went with really small seatstays - my nod to Rob English.

    The problem: it's kind of noodley. IOWs, it's a little too flexy for my weight. It's rideable but, doesn't really go where I want. What I'm wondering is if another top tube would solve the issue? Mr. Brodie, my instructor has advised that I just start over: - "experiment complete, results: small tubing doesn't work on those lengths. Start over." That may be the best course of action but, I want to know IF adding a second TT would solve the problem.

    Lyle Wiens
     

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    Default Re: Noodle-like XL frame problem

    It might help but I agree with Mr. Brodie. Mistakes are always more informative than successes.

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    Default Re: Noodle-like XL frame problem

    Thanks Curt. Yes, the mistake has taught me a lot. It's just hard to come to terms with shelving a frame that I spent so much time and money on. I'll try and look at it as an investment in R&D. If I knew with certainty that adding the second TT would solve the issue, that might change things but, I may end up putting more time and money into a project that produces sub-optimal results.

    Thanks


    Lyle Wiens
     

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    Default Re: Noodle-like XL frame problem

    ST: dropper post tube for 30.9 post just use a rigid post
    TT: 35mm DT cut down to best use of the butting profiles
    DT: 38mm 9/6/9
    SS's: 19mm / 3/4"
    SS's: MTB or Tandem

    I have built quite a few Giant Bikes

    - Garro.
    Steve Garro, Coconino Cycles.
    Frames & Bicycles built to measure and Custom wheels
    Hecho en Flagstaff, Arizona desde 2003
    www.coconinocycles.com
    www.coconinocycles.blogspot.com

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    Default Re: Noodle-like XL frame problem

    Lyle,

    I've built a fair share of double top tube cruisers, as has Steve above...the additional tube alone will not define the performance of the bike.

    The issue you have is the under spec'd rear end.

    While the main tubes may provide sufficient torsional resistance for their diameter and length, the rear end is so diminutive that it undermines the strength of the assembly. If the chainstays/seatstays do not do their part, the main tubes will be stressed beyond their ability to compensate.

    Though you wanted to give a nod to another's design, understand that you need to build holistically for the intended riders size and performance goals.

    You just got more meat than those tiny tubes can handle :)

    Hang it on the wall and begin again.

    cheers,

    rody
    Rody Walter
    Groovy Cycleworks...Custom frames with a dash of Funk!
    Website - www.groovycycleworks.com
    Blog - www.groovycycleworks.blogspot.com
    Facebook - https://www.facebook.com/pages/Groov...s/227115749408

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    Default Re: Noodle-like XL frame problem

    Thanks Rody. I had my suspicions that the rear triangle was related. It's compounded by the length of the stays too.

    I will start over and build something better.
     

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    Default Re: Noodle-like XL frame problem

    Good choice, canít wait to what you come up with :)
     

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