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  1. #1
    B2
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    Custom Geometry Question

    I'm interested in others experiences when coordinating the design for a fully custom frame. I am currently in the process of finalizing the design for a frame for my wife with a high end titanium manufacturer here in the US. My wife has fit data developed with a local fitter (over the last year) which is being used in the design. I was surprised to find out that the manufacturer only changes the TT in 5mm increments. The issue I'm having is that the 5mm steps creates a reach that's either 2.5mm too short or 7.5mm too long. They are also telling me that their fabrication tolerance is 5mm. I guess I'm worried that between the 5mm steps in TT sizing and 5mm fabrication tolerance that we could easily end up with a reach right in middle of two stem sizes.

    Has anyone else experienced this? Does this sound reasonable? If so, I have no problem rolling with it and we'll make it all work somehow. If not, I guess I'll take one more shot with the manufacturer to try and get the TT design down to 1mm increments.

    Thanks,
    Bryan
    Last edited by B2; 2 Weeks Ago at 03:33 PM.

  2. #2
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    -6,-7,-8,-10,-12,-17deg stems all exist. Surely some combination of those angles plus spacers beneath the stem will result in the proper reach.

  3. #3
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    2.5mm is not close enough for you? Really?
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  4. #4
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    Quote Originally Posted by cxwrench View Post
    2.5mm is not close enough for you? Really?
    Like I said, I have no problem rolling with it as long as that's normal. And actually 2.5mm in itself as you have noted isn't that big a deal. My concern was that it sounded like a possible scenario to be off the 2.5mm in design and another 2.5mm in fabrication variance and end up off by 5mm and trying to choose between two stem sizes. It just sounded a little odd to end up in a place like that with a fully custom frame.

    In reality it's not that big of a deal. In addition the manufacturer just told me a few moments ago that the fabrication tolerance for things like reach will be "zero" and not 5mm as he had previously noted (or perhaps I had misunderstood?). So it's really not a big deal now.

    Thanks for putting things into perspective for me.

    Bryan

  5. #5
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    2.5mm is virtually nothing. 7.5mm, depending on your wife's height/reach, could be important especially if she's short. Otherwise, it's easy enough to get a custom, quality TIG welded stem fabricated to any size and angle to get the reach she needs. Tell your wife you did it because you love her. Have it painted her favorite color and she'll be a puddle in your hands.

  6. #6
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    one tenth of an inch, I have never felt my fit was off by even double that much. Stop over thinking the point. Bikes are custom made by people not robots. Trust the builder and enjoy the process. Get off the internet fit sites.

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    High end builders don't become know as high end builders by coming within .75 cm of what's asked of them.
    What you said is definitely not common. I'm nearly certain you misunderstood something and what you said isn't the real margin of error though.

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    to complicate matters, fitting itself is also highly subjective. Your wife may feel fine with a fitting spec now, but her fitting could change latter down the road, could be for the better or the worse. Life is interesting.

  9. #9
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    ^This^...I'll bet the cost of the frame you could go to 5 well respected fitters and come up with 5 slightly different frames. None would be the same.
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    She can feel a pea under the mattress... from the living room couch!
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  11. #11
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    Quote Originally Posted by kiwisimon View Post
    one tenth of an inch, I have never felt my fit was off by even double that much. Stop over thinking the point. Bikes are custom made by people not robots. Trust the builder and enjoy the process. Get off the internet fit sites.
    Beat me to it. People love to overthink stuff

  12. #12
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    Custom Geometry Question-img_20170908_144724092.jpg
    2.5mm not going to make or break the bike.

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    Depends on which contact point for me. My current saddle fore/aft is pretty exact. I've tried 2mm adjustment in either direction, resulting in noticeable discomfort. Reach and stack though I think 2mm would be pretty close to unnoticeable. 5mm on the other hand, my wrists would start complaining.

    Fortunately saddle adjustment is a lot easier than reach adjustment.
    Last edited by ceugene; 2 Weeks Ago at 11:01 AM.

  14. #14
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    5mm increments- Sounds like she is looking at a Moots.
    I know that they only work in 5mm increments.

    If you need down to the mm- get a Kent Eriksen instead. 100% just as good in terms of quality and welds and they will build down to the 1mm.

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    I'm not sure some of you 'get' the nature of the question. Or perhaps I don't.

    I agree that .25 cm is a non-factor but working in .5 increments in no way typical of a custom builder and I think he's asking if custom really means .5 is close enough. No, it doesn't with most builders. Exact may not matter but if you're paying for custom why not get exact.
    Why would a custom builder work in .5 increments. That would lead me to think the pre-cut the tubes. And that would lead me to wonder if they customize angles and furthermore if what they are doing is really custom or if they just offer a sht load of sizes.

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    If I would buy a custom frame because I want to get "the right size", then I wouldn't compromise.
    It's my money, so I would make sure to get exactly what I want -- it might not be what I really need, but that doesn't matter, I would always be annoyed to have made a compromise when I could have gotten exactly what I wanted.

  17. #17
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    My opinion is you're starting in the wrong place.

    You're dumping loads of cash into "data from a local fitter."

    HUGE mistake.

    I would put money down that her fit is not dead on now, after the local fitter, and that it will continue to change over time.

    You are wasting your money with her and custom geometry. Custom geometry is either for those that can't get a normal bike to fit or for those who's fit is incredibly dialed for the long haul. Your wife does not fit either category.

    Custom is not for you or her.
    use a torque wrench

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    Half of you guys need to figure out the difference between 1 cm and 1 mm. 5mm is not 1/2 a cm, hello.

    I can't see where on any bike a .5cm overall difference would make any difference, except in the chain stays.
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    Quote Originally Posted by Got Time View Post
    If I would buy a custom frame because I want to get "the right size", then I wouldn't compromise.
    It's my money, so I would make sure to get exactly what I want -- it might not be what I really need, but that doesn't matter, I would always be annoyed to have made a compromise when I could have gotten exactly what I wanted.
    This is my take on it.

    If I am paying s craftsman to create a custom Anything, I don't want to hear, "Well, I came close." This isn't a government contract. I expect the person to have the engineering and fabrication skills to make exactly what was drawn on paper (or the computer, nowadays.) If not ... why am I paying a premium over a mass-produced, off-the-shelf frame?

    A company which cannot guarantee its work within five millimeters just doesn't care.

    As for whether I could feel that difference .... A.) that's hardly the point, it seems to me and B.) What if I could?

    I know from experience that a couple millimeters makes a Huge difference in seat-post length. After a certain amount of time on a bike, I expect to make fine-tuning adjustments which are so minute they are barely visible ... a coup[le degrees in seat-post height and saddle tilt which someone who Doesn't ride that bike every day might not notice ... but after many months and miles, I do.

    I think reach is a little less important, because there are several "adjustment" systems which can compensate ... waist, elbows, shoulders .... but if I spend the time to get what I find to be the "perfect" geometry for my frame and my riding habits, That is what I want ... not an approximation.

    To me it is mostly an issue of care and craftsmanship, though. if the person could not guarantee any dimension within five mm .... not a very good craftsman ... and the end result could be off in every dimension by that amount, and have almost nothing to do with the frame we agreed on before construction started.

    Quote Originally Posted by aclinjury View Post
    to complicate matters, fitting itself is also highly subjective. Your wife may feel fine with a fitting spec now, but her fitting could change latter down the road, could be for the better or the worse. Life is interesting.
    This is why I wonít get a custom frame. I am at an age where I cannot be sure I will what I will be capable of in five years. If I ride a lot, stretch and bend a lot, if I donít crash and break any bones, if I donít have any other health issues ... I might be in better shape and want more aggressive geometry. If I decay at a normal rate, I might want more relaxed geometry ... and if I have a season like this last, I might lose three monthsí riding recovering from injury and illness and basically need to start over almost fully upright.

    Quote Originally Posted by duriel View Post
    Half of you guys need to figure out the difference between 1 cm and 1 mm. 5mm is not 1/2 a cm, hello.
    Learn something new every day.

  20. #20
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    Quote Originally Posted by duriel View Post
    Half of you guys need to figure out the difference between 1 cm and 1 mm. 5mm is not 1/2 a cm, hello.

    I can't see where on any bike a .5cm overall difference would make any difference, except in the chain stays.
    You've got to be kidding me. If 5mm isn't .5cm what is it? Think about this for more than a couple of seconds before answering.
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    OK, fine have it your way.
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  22. #22
    'brifter' is a lame word.
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    Quote Originally Posted by duriel View Post
    OK, fine have it your way.
    Hey, I didn't make up the metric system...I just learned it properly.
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  23. #23
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    I just cleaned my bike with pledge, now I'm leaving on a 5cm bike ride, I hope your happy!
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  24. #24
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    Quote Originally Posted by duriel View Post
    Half of you guys need to figure out the difference between 1 cm and 1 mm. 5mm is not 1/2 a cm, hello.
    Inches are so much easier to fathom. I mean. Inches are so much easier to 1.8288 meters.
    Attached Thumbnails Attached Thumbnails Custom Geometry Question-duriel.jpg  

  25. #25
    'brifter' is a lame word.
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    Quote Originally Posted by duriel View Post
    I just cleaned my bike with pledge, now I'm leaving on a 5cm bike ride, I hope you're happy!
    Pledge rocks! You must mean 5mm...5cm would take all day!
    I work for some bike racers
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    and a bunch of skateboards

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