26" hardtail geometry- Mtbr.com
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  1. #1
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    26" hardtail geometry

    Hello! I have a tube set to build a steel mountain bike. I want to fillet braze a 26" hardtail in about a size large. This is an ambitious project-- being only my second frame, but I have been practicing!
    I need to build a frame for 26" wheels because I already have wheelset, etc. I was wondering where I might be able to find resources for geometry for the frame. I used to look at old manufacturer catalogues to get ideas for geometry but now it is hard to find companies still making 26" hardtails! Any ideas about where to start to find suggestions on frame angles, tube length, chainstay length, etc? Any suggestions are welcomed.

    Thanks!

  2. #2
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    Essentially these would be the same as a 27.5" hardtail: BB height, front-center and trail, chainstay length. Massage the other elements according to your contact points and wheel size.

  3. #3
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    www.tailcraftcycles.com- they have modern spec....

  4. #4
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    Define your needs and wants. There is no magic geometry that works for everything.
    "These things are very fancy commuter bikes or really bad dirt bikes, but they are not mountain bikes." - J. Mac

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    I searched a little for old frame geometry and couldn't find any. Lots of bike specs... components and such, but I couldn't find old geometry. Rough.

    When I brazed my MTB hardtail frame 20 years ago I rode everything I could get my hands on and then copied the geometry I liked. Trek's front ends at the time were short and quick which matched my riding style coming from BMX, but Specialized's rear ends felt more stable riding out of the saddle which I did a lot (again, coming from BMX).

    I guess that's hard to do when 26" frames are few and far between.

    have you asked your local bikes shops for old catalogs? I used to wrench at shops, there is likely one old coot or nut in the back who has a collection... seemed like every shop had one of those guys.

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    copy the surly instigator, spot on geo and does 275 too

  7. #7
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    Regardless of wheel size, you'll need an idea of what you are going for first. 90's style NORBA race geometry? Super slack/long/long aggro modern hardtail? Something else? What trails/terrain are you going to ride on this bike?

    Without some idea of what you're trying to build, there's no point in us throwing around numbers and angles.

    If you don't have much of a handle on what you want, it's time to go demo some bikes and keep track of how they ride. Jumping into building something without a good idea of what the end result needs to be is a great way to waste your time.

    -Walt

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    To that same end Walt, it is his second frame... don't sweat the details, just build. In the end it may not even be ride-able. I build 4 before I was comfortable calling them "bike frames".
    My carbon fiber full suspension frame build blog:
    https://carbonmtb.blogspot.com/

  9. #9
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    Quote Originally Posted by tgwms View Post
    To that same end Walt, it is his second frame... don't sweat the details, just build.
    Well, but he *asked* for geometry info! He *wants* to sweat those details. Why not at least *try* to make something good? He's not just making practice joints here, it's a bike he'll ride. There's absolutely no reason to "not sweat" the geometry and just slap something together.

    Good lord.

    -Walt

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    Sure there is good reason to not overthink the details... was your second frame trail worthy Walt? I made all sorts of mistakes the second time around. Yes I built it up and rode it around the street, but it would have been unsafe on the trail.

    The point being, making a close estimate of geometry to simply move the project forward and learn the art of building a frame [and geometry] is a completely reasonable suggestion. It is not unthinkable that a third or fourth attempt will be required before pointing it downhill.

    OP did ask for "any suggestions".
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  11. #11
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    My second frame was most certainly trail worthy (my wife still rides my first occasionally, too). There are of course lots of things I'd change about all my frames from 15 years ago given what I know now - but they have all been *safe* to ride on their intended terrain. It's really not hard to get to that level of competence (at least with steel) if you do even a little joinery practice first.

    I guess everyone is different. I see the main draw of building your own frames as the chance to do the exact geometry/fit/style that you want - the building itself is just a necessary step that's sometimes kinda fun and sometimes just annoying. If the construction itself is what you find satisfying and you don't care much about the geometry, that's fine, of course.

    -Walt

  12. #12
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    Quote Originally Posted by taylorbena View Post
    Hello! I have a tube set to build a steel mountain bike. I want to fillet braze a 26" hardtail in about a size large. This is an ambitious project-- being only my second frame, but I have been practicing!
    I need to build a frame for 26" wheels because I already have wheelset, etc. I was wondering where I might be able to find resources for geometry for the frame. I used to look at old manufacturer catalogues to get ideas for geometry but now it is hard to find companies still making 26" hardtails! Any ideas about where to start to find suggestions on frame angles, tube length, chainstay length, etc? Any suggestions are welcomed.

    Thanks!
    here ya go buddy, somewhat generic 'fun' hardtail geometry. A trail hardtail for a 5'10 170lb dude to enjoy intermediate/advanced singletrack. Easy for anyone to adapt to. Should play nice with a 50-60mm stem, and adapt to 650b OK if you decide to go that route in the future. 750mm bars, minimum, to keep the steering right. Designed around a 522mm A-C fork (130mm 650b). Raise the BB a bit if you use flat pedals.

    Generic tubing advice is 31.8 TT and 34.9 DT, in 9/6/9.

    26" hardtail geometry-genericlarge.jpg
    (shown at 0 sag)

    This is just a place to start, and your preferences, riding location, height/weight, etc change things- possibly dramatically. (and it's crazy-progressive if you haven't ridden a modern mtb.) 650b is the same as 26", just figure 10mm difference in BB height.

    Frames are designed holistically, i don't think you can steal a design aspect from a bike and another aspect from a different one and understand how it's going to turn out.

    For my part, I really REALLY like hardtails, and i've built several, but i'm just a hobbyist. Don't take advice from me. I just like to talk hardtail, and i'm posting recommendations to get the discussion ball rolling.
    "Things that are complex are not useful, Things that are useful are simple."
    Mikhail Kalashnikov

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    Thanks for all the great responses. I have a lot of leads to follow! I didn't realize how close the geometry is between 26" and 650b. That is great news. The first frame I build was lugged so the angles were pretty well predetermined. I have a pretty good idea about what I want for a bike; a responsive xc frame. I am going to need to find a fork. Maybe 100-120mm. I'll let you know what I decide. Thanks!

  14. #14
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    Quote Originally Posted by taylorbena View Post
    Thanks for all the great responses. I have a lot of leads to follow! I didn't realize how close the geometry is between 26" and 650b. That is great news. The first frame I build was lugged so the angles were pretty well predetermined. I have a pretty good idea about what I want for a bike; a responsive xc frame. I am going to need to find a fork. Maybe 100-120mm. I'll let you know what I decide. Thanks!
    100mm fork, 26" wheelset, and 'responsive xc frame' speaks of someone whose missed 10 years of mtb development.


    What 'a responsive xc frame' translates now in terms of geometry is very different from the old 71/73* 100mm stem bikes of yesteryear, or even what was common 5 years ago. If you're not up to date on mtb geometry you're likely to build yourself an homage to an awful era. My opinion only, obviously.

    I kinda feel like it's not worth building a frame until you're at the pointy end of knowing what's out there and what you like. If you're only familiar with the old garbage you're better served buying a modern production frame unless you just wanna do it just because. Which is still cool; your first fillet brazed frame might come out weird anyway.
    "Things that are complex are not useful, Things that are useful are simple."
    Mikhail Kalashnikov

  15. #15
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    As already suggested, Stop and revise where the MTB has now progressed too. Unfortunately, 26" is not a 'supported ' technology now, though, as sugested, 27.5 is not far from the ball park for you. Seat tube angles are now steeper, front centers have grown significantly, and head tube angles are slacker.
    Look for 650B/27.5" forks, as you can move into the next generation wheel size without problems once the 26" wheels require re-rimmed or replaced. Make room for the larger wheel size in the rear triangle and you will future proof your build.

    Otherwise. have fun designing that new bike.

    Eric
    If I don't make an attempt, how will I know if it will work?

  16. #16
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    Quote Originally Posted by taylorbena View Post
    a responsive xc frame. I am going to need to find a fork. Maybe 100-120mm.
    26" hardtail geometry-genericlarge2.jpg

    Here ya go. Drop it down to a 28.6 top tube to keep the right amount of flimsy. BB was raised a bit to suit east coaster preference (although i don't get it). 10mm longer stem, same wide bars.

    It's a suggestion, and a modern interpretation of old values. Personally i see vanishing returns shortening the wheelbase much further than this, assuming you actually ride the bike on trails occasionally. (and don't have a super refined taste in what you like, but then you wouldn't be polling the forum!) The first model is a better, more versatile bike, imo.

    I'm just pasting screencaps from bikeCAD. There's a free version of the software available on his website, but it's a pain to get going because it's Java. I'm happy to send you files of the nonsense i've mocked up.


    For what it's worth, my current hardtail was designed around 650b, but i've been using 26" wheels on it 'temporarily' and they're great. Not really pedal strikey at all. They're just not that different.
    "Things that are complex are not useful, Things that are useful are simple."
    Mikhail Kalashnikov

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    Thanks Scott; very helpful. And I dig your Kalashnikov quote. Another of his which is fairly relevant here:
    [...]before attempting to create something new, it is vital to have a good appreciation of everything that already exists[...]
    My carbon fiber full suspension frame build blog:
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  18. #18
    pvd
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    That's a very antiquated design. I'm 5'10 and this bike is working great and would do well for basic XC with slight adjustment. It's an easy design adjustment to put a smaller fork on it and shrink the wheels but the other parameters remain similar. Certainly, with 26" wheels the bike would need to be even a little longer.


  19. #19
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    Also, never set out to build a $hit bike. Build the best bike you possibly can every time. Design is the most important detail of all and the one very few ever learn.

  20. #20
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    Quote Originally Posted by pvd View Post
    That's a very antiquated design.

    I dunno. For me there's a range of about 40mm of hardtail front-center that i could see myself using, depending on the application. Conservative designs appear antiquated because we're revising front-center lengths up to where they really should have been, but i think 'antiquated' is a perspective from this moment, and not for frame design in general.


    Personally, i don't really wanna own that 2nd bike i posted up, but i don't want to own yours either. Built both, happier with something between them. But that's me and i'm not everyone. And you're right, pushing the front end out and designing around a big fork has surprisingly few downsides (for an experienced rider in california).

    PS your data plates are AWESOME.
    "Things that are complex are not useful, Things that are useful are simple."
    Mikhail Kalashnikov

  21. #21
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    Quote Originally Posted by taylorbena View Post
    Hello! I have a tube set to build a steel mountain bike. I want to fillet braze a 26" hardtail in about a size large. This is an ambitious project-- being only my second frame, but I have been practicing!
    I need to build a frame for 26" wheels because I already have wheelset, etc. I was wondering where I might be able to find resources for geometry for the frame. I used to look at old manufacturer catalogues to get ideas for geometry but now it is hard to find companies still making 26" hardtails! Any ideas about where to start to find suggestions on frame angles, tube length, chainstay length, etc? Any suggestions are welcomed.

    Thanks!
    What trails? Name 3or4 of your faves
    video=youtube;][/video]...

  22. #22
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    Kinda looks like my 29ht...(sweet pvd)

    Quote Originally Posted by scottzg View Post
    I dunno. For me there's a range of about 40mm of hardtail front-center that i could see myself using, depending on the application. Conservative designs appear antiquated because we're revising front-center lengths up to where they really should have been, but i think 'antiquated' is a perspective from this moment, and not for frame design in general.


    Personally, i don't really wanna own that 2nd bike i posted up, but i don't want to own yours either. Built both, happier with something between them. But that's me and i'm not everyone. And you're right, pushing the front end out and designing around a big fork has surprisingly few downsides (for an experienced rider in california).

    PS your data plates are AWESOME.
    Agreed, no way something~ 64* ha for xc not even with 51mm offset (is there a 26 fork @120mm w/ that offset?)...the 2nd one is close for ha, For "xc", and not knowing what trails, I'd suggest 66.5~67ha w/ 120mm fork (just no steeper, external cup headtube and not 100mm travel)
    video=youtube;][/video]...

  23. #23
    pvd
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    Ok. Just be productive, I went and prepared a quick sketch of what a modern 26" XC bike would look like. I would certainly put a bit more work into it if I were serious about making it.

    It's not pretty but it'll probably work.

    Still, you're really making a mistake by doing a 26" hardtail. That shit is dead. It's pushing against any parts you'd be able to find for it. You'll just end up spending a lot of good money after bad. Not a wise move for a novice.

    Bits of advice for the aspiring framebuilder | Peter Verdone Designs


  24. #24
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    Some good advice above

    Quote Originally Posted by Deerhill View Post
    ...26"~67ha w/ 120mm fork (...
    ^^made myself throw up a little for typing it, have to take that back...gotta be over 140mm, at the very least 530a2c
    video=youtube;][/video]...

  25. #25
    pvd
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    This thread sent me down a wormhole..

    Kids bikes | Peter Verdone Designs

  26. #26
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    Quote Originally Posted by pvd View Post
    Ok. Just be productive, I went and prepared a quick sketch of what a modern 26" XC bike would look like. I would certainly put a bit more work into it if I were serious about making it.



    What was your reasoning for such a tall head tube in this design? Why do you prefer that arrangement over a riser bar?

    Thanks for the insight!
    "Things that are complex are not useful, Things that are useful are simple."
    Mikhail Kalashnikov

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