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  1. #1
    Yo no fui.
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    Halp with the geometry on my custom "dirt road bike" frame!

    I'm having a custom "dirt road bike" built and would love some comments on the geometry, which is a bit beyond my knowledge.

    I currently ride a 54 cm Gios A-90, which I love. The geometry of the Gios is here: http://www.gios.it/2005/eng/prima.php?page=newA90-specs

    My new frame will have the following angles/lengths in the picture.

    Any thoughts would be helpful. Thanks!
    Attached Thumbnails Attached Thumbnails Halp with the geometry on my custom "dirt road bike" frame!-bike.jpg  
    Last edited by Pablo; 10-20-2009 at 12:39 PM.
    "It is better to conquer yourself, than to win a thousand battles." -Dhammapada

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  2. #2
    wim
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    Well,

    the values listed for fork rake and subsequent bottom bracket are bizarre—the bike will be unrideable. More seriously, reposting with correct numbers would help others in coming up with a meaningful response.

  3. #3
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    Quote Originally Posted by wim
    the values listed for fork rake and subsequent bottom bracket are bizarre—the bike will be unrideable. More seriously, reposting with correct numbers would help others in coming up with a meaningful response.
    Unrideable! That sounds serious. I'll post a pic.
    "It is better to conquer yourself, than to win a thousand battles." -Dhammapada

    "Fact is only what you believe; fact and fiction work as a team." Jack Johnson

    "A true cyclist sometimes has to bite the dust before he can reach the stars.” Laurent Fignon

  4. #4
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    if your running flat bars not drops thats going to be too small. whos building it? I would suggest having this discussion with an experienced framebuilder

  5. #5
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    Quote Originally Posted by carlhulit
    if your running flat bars not drops thats going to be too small. whos building it? I would suggest having this discussion with an experienced framebuilder
    I will be having these discussions with the framebuilder, but I was hoping for some thoughts form the peanut gallery.

    It will have drop bars . . . what part will be too small???
    "It is better to conquer yourself, than to win a thousand battles." -Dhammapada

    "Fact is only what you believe; fact and fiction work as a team." Jack Johnson

    "A true cyclist sometimes has to bite the dust before he can reach the stars.” Laurent Fignon

  6. #6
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    I built mine more or less along the lines of a cross bike - slightly soft head tube angle, higher bottom bracket and a ton of clearance for fenders and bigger tires. Aside from that I matched it exactly to what I ride normally on the road. There shouldn't be any reason to change, surfaces are surfaces and fit is fit. Without looking at what you ride today, what you're showing makes sense to me aside from the chainstay length which seem a bit short for a bike with that purpose.
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  7. #7
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    Quote Originally Posted by terry b
    I built mine more or less along the lines of a cross bike - slightly soft head tube angle, higher bottom bracket and a ton of clearance for fenders and bigger tires. Aside from that I matched it exactly to what I ride normally on the road. There shouldn't be any reason to change, surfaces are surfaces and fit is fit. Without looking at what you ride today, what you're showing makes sense to me aside from the chainstay length which seem a bit short for a bike with that purpose.
    Thanks for your thoughtful observations. I recall your bike, which was a bit of an inspiration for me, less the travel couplers, which I don't need and wouldn't make use of.

    By the way, are you happy with cantelever brakes? I was going to go with long reach calipers as I doubt I'll ever ride tires bigger than 32s (If I need bigger, I'd probably take my rigid 29er), but I'm wondering about cantis. Thanks.
    "It is better to conquer yourself, than to win a thousand battles." -Dhammapada

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    "A true cyclist sometimes has to bite the dust before he can reach the stars.” Laurent Fignon

  8. #8
    wim
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    Nice bike!

    Agree with terry b's slightly soft head tube angle preference. With the right fork, that should calm down handling nicely. Comes in handy when you hit one of those invisible soft, sandy spots—like I did this morning riding my skinny-tired road bike down a dirt trail.

  9. #9
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    Quote Originally Posted by wim
    Nice bike!

    Agree with terry b's slightly soft head tube angle preference. With the right fork, that should calm down handling nicely. Comes in handy when you hit one of those invisible soft, sandy spots—like I did this morning riding my skinny-tired road bike down a dirt trail.
    Thanks.

    So are you referring to the 72.5 degree number? Would a "softer" angle be a smaller number, e.g. 70?
    "It is better to conquer yourself, than to win a thousand battles." -Dhammapada

    "Fact is only what you believe; fact and fiction work as a team." Jack Johnson

    "A true cyclist sometimes has to bite the dust before he can reach the stars.” Laurent Fignon

  10. #10
    wim
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    Quote Originally Posted by Pablo
    Thanks. So are you referring to the 72.5 degree number? Would a "softer" angle be a smaller number, e.g. 70?
    Yes, I'm referring to the 72.5 degree head tube angle. And yes, a smaller angle would be "softer," but you have to be careful here not to stray into goofy territory. Keep in mind that steering characteristics depend on just more than head tube angle. So-called fork rake (also called 'offset') and, to some degree, fork length interact with head tube angle to form trail, which determines how steering feels. It's all a bit complex when you first look at it, but actually fun to figure out. Dave Moulton's explanation is one of the best on the web and, in my view, would be very helpful to you. If I were designing a frame, I'd read as much of Dave's stuff as I could...

    http://davesbikeblog.blogspot.com/20...le-bit-of.html

  11. #11
    eminence grease
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    I ended up with long reach calipers. I do have cantis on my cross bike, and they're "good enough" but I definitely prefer the calipers. I'm getting a lot of mileage on the roads with both in the crappy Chinese traffic so I've had a chance to do some continuous comparisons. Calipers win, but I am considering ponying up for the Shimano version, the Tektros I'm using are okay, but I wonder if there is more grab on the more expensive version.
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  12. #12
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    There's not enough information and your question is too general. From the information provided, no one here would be able to determine whether the frame will fit you.

    From what I can tell, the bike is made for 'cross width tires and perhaps cantilever brakes.

    The front end (head angle) is tamed down say, half a degree to make it better handling on dirt roads. The rest is pretty normal stuff. Except for all the curvy tubes. Coconino Cycles, perhaps?

    You really should be posing your questions to the builder.

  13. #13
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    Quote Originally Posted by Peter P.
    There's not enough information and your question is too general. From the information provided, no one here would be able to determine whether the frame will fit you.

    From what I can tell, the bike is made for 'cross width tires and perhaps cantilever brakes.

    The front end (head angle) is tamed down say, half a degree to make it better handling on dirt roads. The rest is pretty normal stuff. Except for all the curvy tubes. Coconino Cycles, perhaps?

    You really should be posing your questions to the builder.
    I was obviously not asking if it would fit me, that would be a stupid question as I provided no info on my dimensions. Thanks for the info on the head angle.
    "It is better to conquer yourself, than to win a thousand battles." -Dhammapada

    "Fact is only what you believe; fact and fiction work as a team." Jack Johnson

    "A true cyclist sometimes has to bite the dust before he can reach the stars.” Laurent Fignon

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