Getting ready to dive in......- Mtbr.com
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  1. #1
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    Getting ready to dive in......

    I'm getting ready to take the plunge and make my own frame. I just want some experienced eyes to make sure what I'm about to build will at the very least be rideable. I'm going for a conservative trail bike that I can do some big xc rides and races on.

    A lot of the geometry is based off my two current hardtails and what I like and dislike about them. My trails are tight and somewhat smooth so nimbleness and flick-ability are more important than high speed stability. Long climbs are a part of life and I am hoping to minimize wheel flop and keep a comfortable climbing position. I am 5' 10.5" with a 31" inseam.

    The frame is based off a 120mm fork sagged 20mm.

    Seat post dimensions and seat height are modeled after a rock shox reverb 170.

    Am I about to end up with a giant paperweight?

    Getting ready to dive in......-img_8025.jpg


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  2. #2
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    Make sure your fork crown clears the downtube. Wheelbase and front center/chainstay length are all on the long side for "nimbleness", but that's pretty subjective. That's a very high BB for smooth trails.

    Otherwise, sure, go for it.

    -Walt

  3. #3
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    Quote Originally Posted by Walt View Post
    Make sure your fork crown clears the downtube. Wheelbase and front center/chainstay length are all on the long side for "nimbleness", but that's pretty subjective. That's a very high BB for smooth trails.

    Otherwise, sure, go for it.

    -Walt
    I guess I should specify that the trails are naturally smooth. No banked turns or jumps, just small rocks and roots around. Narrow is our tech.

    I went back and fourth on the bb height and bb drop. I want the bike to feel poppy, and have an "on top" feel rather than "sitting inside" and this was what I came up with. Is there a way to lower the bb height without increasing bb drop by the same amount?


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  4. #4
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    Quote Originally Posted by Little_twin View Post
    Is there a way to lower the bb height without increasing bb drop by the same amount?
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    What? I guess you could use smaller wheels... but otherwise, no. It's a math thing.

    Generic hardtails hover around (sagged) 305mm BB height. You're 20mm higher than that which is a LOT for pedal strike purposes. I don't know what "narrow is our tech" means for pedal strikes, nor do I know why you want to feel "on top" of the bike. Keep in mind that until you have pedal strike problems *lower is always better*. Quicker handling and more stability - it's the only free lunch available in mountain bike geometry.

    -Walt

  5. #5
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    Getting ready to dive in......

    Quote Originally Posted by Walt View Post
    What? I guess you could use smaller wheels... but otherwise, no. It's a math thing.

    I don't know what "narrow is our tech" means for pedal strikes, nor do I know why you want to feel "on top" of the bike.

    -Walt
    That was what I thought. Wasn't sure if I was missing something. I'm pretty committed to 29 so no smaller wheels.

    The trails I ride the surface is very chattery with little chunk. If it weren't for the fact that most are razor thin and on steep hillsides/ cliffs they wouldn't be very hard.

    The "on top" feeling is just what I'm used to from my xc bikes.

    By no means do expect to get everything right on the first try. I just want to set myself up to not repeat the same mistakes over and over. I appreciate the input.




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  6. #6
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    Quote Originally Posted by Walt View Post
    What? I guess you could use smaller wheels... but otherwise, no. It's a math thing.

    Generic hardtails hover around (sagged) 305mm BB height. You're 20mm higher than that which is a LOT for pedal strike purposes. I don't know what "narrow is our tech" means for pedal strikes, nor do I know why you want to feel "on top" of the bike. Keep in mind that until you have pedal strike problems *lower is always better*. Quicker handling and more stability - it's the only free lunch available in mountain bike geometry.

    -Walt
    “Lower is always better”...I ride many of the same trails as the OP. I honestly can’t tell you what my bb height is but, it’s too low for the trails I ride. I’m on a 2018 SC Bronson, and I get multiple pedal strikes every ride...low and slack isnt for everyone

  7. #7
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    The trails I ride are tight and twisty to the extreme. We have very little vertical. OP, is that a good description of your trails? Slack steering is great for stability on downhills but if you don't have vertical, you don't need a headtube as slack as you have there. I demo'd a bike a while back with a headtube that was somewhere around 68 degrees. I hated it. It fought me through every turn. If you want to be quick in the twisty stuff, tighten up the front end.
    I also hate pedal strikes. A quick measure shows my BB at 345mm above the ground. I pedal through everything and can count my pedal strikes from the last two years on one hand. I do sit high on the bike but it took all of 30 minutes to forget about any differences with the old bike.
    I went extreme in the opposite direction from current trends and I won't go back.
    Build the bike for the trails you will be riding and keep in mind that the the proper tool for the job doesn't look the same for every trail.

  8. #8
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    We have LOTS of vertical. I went low with the bb and am thinking it could have been a little higher. That said a quick ride around the neighborhood tells me that the handling is very close to what I was going for.

    It's not pretty, but it works and I learned a lot. This one will get ridden a bit, see if any changes need to be made, then apply those to #2.

    Getting ready to dive in......-img_8423.jpg


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  9. #9
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    Quote Originally Posted by griz View Post
    “Lower is always better”...I ride many of the same trails as the OP. I honestly can’t tell you what my bb height is but, it’s too low for the trails I ride. I’m on a 2018 SC Bronson, and I get multiple pedal strikes every ride...low and slack isnt for everyone
    Please read the whole sentence: "Keep in mind that until you have pedal strike problems *lower is always better*."

    Note that first "until you have pedal strike problems" part.

    -Walt

  10. #10
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    Awesome work! Got to get some cable guides and paint on it now.

    Don't expect the Geo of your first frame to be everything you wanted starting out. Getting bikes to handle like you want them to based on the numbers is a process.

    It seems like every builder has their own areas of attention that help make their bikes a product of themselves and their customers. I happen to really like higher bottom brackets for the riding in the mountains around here. I seem to attract customers that also want that, so it all works out. Definitely ride your bike on the trails a bit before heading back to the drawing board though.

    Post process pics if you took any!
    Myth Cycles handbuilt bike frames
    Durango, CO
    http://www.mythcycles.com

  11. #11
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    Quote Originally Posted by Erichimedes View Post
    Awesome work! Got to get some cable guides and paint on it now.

    Don't expect the Geo of your first frame to be everything you wanted starting out. Getting bikes to handle like you want them to based on the numbers is a process.

    It seems like every builder has their own areas of attention that help make their bikes a product of themselves and their customers. I happen to really like higher bottom brackets for the riding in the mountains around here. I seem to attract customers that also want that, so it all works out. Definitely ride your bike on the trails a bit before heading back to the drawing board though.

    Post process pics if you took any!
    It doesn't ride exactly like I expected but it doesn't ride poorly so I'll call that a win. It's certainly not the prettiest frame out there either. Lots of mistakes were made and even more lessons learned. Here are the few build pictures I got. I spent enough time standing around staring at things that I really should have gotten more pictures.










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  12. #12
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    Getting ready to dive in......

    Since completing #1 I got started and have almost finished #2. Frame 2 is a gravel bike designed around a 650b x 1.9 or 700 x 42. It has a longer than average reach as I prefer stems in the 60-70mm range.














    I felt like this frame went much better. My miters were much tighter and more accurate, and my welding got a good bit better as well. This frame took me about 1/3 of the time that #1 took and was able to apply all of what I learned to make this one better. I still have to ream and face the headtube as well as ream the seat tube and it'll be ready to get painted.

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  13. #13
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    Awesome! Great that you're building a second frame. There's just no way around the fact that the second frame will always go easier/smoother than the first. Just got to get in there and do it, and it all starts to make sense.
    Myth Cycles handbuilt bike frames
    Durango, CO
    http://www.mythcycles.com

  14. #14
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    I always tell framebuilding students some variation on, "Your first frame will be amazing and fun and you'll love building it and riding it. And in a year when you've built 3 or 6 more, you'll be horribly embarrassed by it."

    The best builders (both amateur and pro) are never quite satisfied. I look at bikes I built 10 or 15 years ago and can't think of anything but all the stuff I'd do differently now. I imagine I'll be doing the same in another 10 years about the stuff I'm building now.

    -Walt

  15. #15
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    Just wrapping up frame #3 and starting to feel like I'm figuring things out.

    Getting ready to dive in......-img_9424.jpgGetting ready to dive in......-img_9440.jpgGetting ready to dive in......-img_9443.jpg
    Getting ready to dive in......-img_9456.jpgGetting ready to dive in......-img_9459.jpgGetting ready to dive in......-img_9463.jpgGetting ready to dive in......-img_9464.jpg


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  16. #16
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    Good looking builds! Is that a diy jig?

    thanks, Brian

  17. #17
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    Quote Originally Posted by calstar View Post
    Good looking builds! Is that a diy jig?

    thanks, Brian
    Thanks, I just keep trying to learn with each frame.

    The jig is a brew bikes jig.


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