Custom Ti singlespeed geo feedback - - 726 F/C, 446 Reach, etc..- Mtbr.com
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  1. #1
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    Custom Ti singlespeed geo feedback - - 726 F/C, 446 Reach, etc..

    Not sure if this type of request for input is welcomed here. I totally appreciate your professional abilities and insights and recognize (as a freelancer myself) that pros should be compensated for expertise

    Any input from the community is welcomed..

    It's my first custom frame. I look forward to sharing the finished product and my thoughts on this geometry in late March, after getting some trail time.

    For now, some re-assurance that I'm not crazy, would be appreciated. This design is not inspired by a specific bike, but rather what issues I had with 3 years on a Pivot LES SS . And a couple months on Canyon Dude fatbike (more 'modern' geo than LES) has me convinced that I like more reach, more front/center, steeper STA.. hence I think I'm a belieber in 'long,low,slack' or whatever new school geo is called.

    The builder, to be named, has been great to work with so far. Yet we are not local to each other, so a proper fitting and consultation has not been done.

    About me:
    New England classic trails- rooty, tech, up and down , tight..etc.
    5'10" , 30" length pants (haven't measured acutal inseam- 29"?)
    I ride and race singlespeed exclusively. XC and Endurance.
    Occasional gears for bikepacking
    160mm dropper, Revive

    Reach 446
    Front/Center 726
    Stack 625
    STA 74.5
    HTA 68
    CS 420 (slammed) (typo corrected)
    wheelbase 1140
    BB height 305mm (12")

    I am most nervous about the wheelbase and front/center #s ... I am concerned about the lack of agility in tight trails, though this is not based on anything solid.

    thank you

    Custom Ti singlespeed geo feedback -  - 726 F/C, 446 Reach, etc..-maynard_custom_-_2019_build.jpg

  2. #2
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    If you're going to second-guess your builder by consulting random internet strangers (Dunning-Kruger effect, hello!), good luck.

    Even if everyone here was a geometry genius, we don't know much about the inputs to this design process. I could critique this design, but I'd just be spitballing.

    -Walt

  3. #3
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    Understood Walt. I guess I'm looking for spitbaiting, with full understanding that the Dunning-Kruger effect may be at play (had to google that one). I've lurked enough here to know that there is some type of philosophy around the 'modern geo' approach. If anyone experience designing sees a red flag here, I'd like to know.

    I gave my builder these numbers along with a bunch of geo listings of inspiring bikes, yet haven't received any specific recommendations for changes. I guess that's a good sign..or maybe I'm sounding too confident and just haven't asked.

    thanks

  4. #4
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    Wait, did you design it, or did the builder?

    -Walt

  5. #5
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    I designed it


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  6. #6
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    Not far off a Specialized Epic, just with a slacker head tube angle. I prefer a higher bb and longer chain stays on a single speed so I can pedal through and over more stuff without as many drastic body position changes.
    I like bikes

  7. #7
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    Then own it, dude. Only one way to see how it rides, which is to pull the trigger.

    If you want professional design help, you're going to have to cough up $ and spend some time as well talking with the designer.

    Is this ChiTi?

    -Walt

  8. #8
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    Not chITi. Okay, I own it !

    Interesting comparison to the Epic. Iíve stayed away from comparing to full suspension, as rear travel just adds another mind fíing element to thinking about geo.

    Regarding Bb height and CS...
    Bb height is modeled after Pivot Les - low admittedly, but Iím used to it and wonít strike much
    chain stay is certainly on the short side. Yet with a long front I am confident Itís a recipe for goodness.




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  9. #9
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    MTBR- where opinions are free! Here's mine...

    (Walt I respect your discretion on the wide variety of conversations that exist here.)

    Quite similar to the Kona Honzo, which has a bit of a cult following and generally very well received. KONA BIKES | MTB | HONZO | Honzo ST

    I've ridden that bike in a couple forms (the geo changes slightly depending on frame material, wheel size, and setup) It's awesome but the BB is too low. Pedal strikes are frequent. On a SS this problem would be amplified greatly.

    Note: You didn't say what fork you're planning on running. This could change things dramatically. 483mm A-C carbon rigid fork vs. 140mm suspension fork will change the BB height.

    Everything else looks pretty good. (BTW you have a typo on the chainstay length- 720 chainstays? I'm assuming that's supposed to be 420?)

    I'm a pretty avid rider/racer and spend most of my time on a SS. I had my first custom frame built 2 years ago. I was targeting "modern XC geo" which wasn't dis-similar to the Kona Raijin. KONA BIKES | MTB | MTB HARDTAIL | Raijin Longer reach, longer chainstay (unfortunately), same HTA, 55mm BB drop with 180mm cranks (I'm 6'3" and ride XL frames), and 73 STA.

    This frame was designed as a rigid SS first and foremost. I did put a 120mm Fox 34 on it last year for one specific race, but otherwise it's only every been ridden with no suspension, no gears, and no dropper, but the frame is designed to do also accept all of those options.

    It's great, I really love the frame. The only thing I'd change is the chainstay length, slightly shorter would be welcome.

    My BB height with 2.4/2.6 tires is a bit over 13" with a 483mm A-C carbon Whiskey fork. (EDIT: I later realized that measurement was with the 120mm suspension fork still installed, not the rigid 483 fork) That's with a 55mm BB drop and 435mm chainstay length with my current chainring/cog combo, 427 ish shortest possible. I would not consider going any lower with my 180 cranks.

    In other words if I were you, I would raise that BB significantly. There's an important relationship between BB height and chainstay length when you start going to shorter chainstays (which I'm a big fan of), maybe anything less than 430 ish.

    You want to be able to keep the front end down on a seated climb scenario, but for a SS setup you'll be standing and that won't matter.

    Hopefully I didn't leave anything out, but those are my thoughts. For the record I ride upstate NY trails, love tech, love racing, love steel frames and SS. I'm happy to share my experience.
    Last edited by *OneSpeed*; 02-07-2019 at 07:54 AM.
    Rigid SS 29er
    SS 29+
    Fat Lefty
    SS cyclocross
    Full Sus 29er (Yuck)

    Stop asking how much it weighs and just go ride it.

  10. #10
    pvd
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    It's terribly old fashioned and could use a lot of work.

    Here's a bike I did for my wife. It's pretty conservative and she's 5'6" tall.

    PVD Glamorous Glennis | Peter Verdone Designs



    Also, titanium is a horrible material to experiment with and really not worth the cost.

    Also, you've got some tire clearance issues.

    These days, I'm doing 74 degree effective seat tubes for hardtails. Hardtails are not FS race bikes so save the story about what Pole is doing. 74 is comfortable but still very lively. Go steeper at your peril, especially in NE....unless you're a hardcore racer.

  11. #11
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    Beautiful bike PVD.
    I'm not sure what's going on with tire clearance on my drawing.. it may be with 2.6s .. need to look into it.
    Perhaps 'old fashioned' but I'm not ready to jump into a longer front/center than 725 .. that would definitely be experimenting, Maybe next time- when your design ethos catches on and I can try something similar off a shelf somewhere.
    thanks for your thoughts

  12. #12
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    Quote Originally Posted by *OneSpeed* View Post

    In other words if I were you, I would raise that BB significantly. There's an important relationship between BB height and chainstay length when you start going to shorter chainstays (which I'm a big fan of), maybe anything less than 430 ish.

    You want to be able to keep the front end down on a seated climb scenario, but for a SS setup you'll be standing and that won't matter.
    Thanks for thoughts OneSpeed. Can you elaborate on this? How does short 420 CS impact front end planted, with a low 12" BB ? If I like a 12" BB on a Pivot LES with a 435 CS, why would a 420 CS make the feeling of the low 12" BB different?

    And.. this is designed around a FOX 34 SC 120mm . 531mm with 20% sag.

  13. #13
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    Quote Originally Posted by adinpapa View Post
    Thanks for thoughts OneSpeed. Can you elaborate on this? How does short 420 CS impact front end planted, with a low 12" BB ? If I like a 12" BB on a Pivot LES with a 435 CS, why would a 420 CS make the feeling of the low 12" BB different?

    And.. this is designed around a FOX 34 SC 120mm . 531mm with 20% sag.
    There's a lot of variables. Every time you change one parameter you're actually changing 3 (or more) things.

    If you have short chainstays, sub 420, and a high BB (say 40mm drop) your Center of Gravity will be too high on a steep grade while doing a seated climb on a geared bike and it would be hard to keep the front tire down. A "slack" STA would accentuate this, 72-73 degrees.

    On a SS your standing on climbs, short chainstays are an advantage in this scenario and give you more grip when your weight is shifted forward. BB height is less critical.

    Are you running 175mm cranks on your Les? I'm surprised to see your current bike has that low of a BB. Have you measured it with your current setup? Yes, generally the shorter the chainstays, the lower the BB needs to be, and the STA should come forward proportionally. Likewise old school XC bikes were 71/73 with longer chainstays.

    I agree with your opinion in the OP that a longer reach, longer FC, shorter stem, and a slacker HTA is a good thing and fun to ride. Personal preference, setup (including crank length), riding style, etc. all plays a part.

    Looking at your numbers the BB height was the only parameter that stood out as a red flag. If it's not a problem for you now then do what you feel is right. That is quite low IMO unless you're running short cranks.
    Rigid SS 29er
    SS 29+
    Fat Lefty
    SS cyclocross
    Full Sus 29er (Yuck)

    Stop asking how much it weighs and just go ride it.

  14. #14
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    I posted my first couple frame designs on here for critiques before i built them. I got truly fantastic advice on which tubes to use, great advice on construction stuff, and a shitshow of replies regarding geometry. I was zeroing in on what geo worked best for ME riding MY TRAILS in MY STYLE, and i thought i was finding some greater truth. Nah. (there's like 8 production frames available now that mirror my fave hardtail geo)

    You've gotten well informed, quality replies from 2 people that are suggesting what i think is nonsense, and a third who isn't offering an opinion... but i'd disagree with him too. Their truth isn't my truth. Taking 5 opinions and smudging them together is stupid. If you want something you can't buy from a production line... strike out on your own. I only suggest you design it with adjustable CS length and room to adjust bar height.


    I think you're measuring your leg length wrong.
    "Things that are complex are not useful, Things that are useful are simple."
    Mikhail Kalashnikov

  15. #15
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    Quote Originally Posted by scottzg View Post
    i thought i was finding some greater truth. Nah. (there's like 8 production frames available now that mirror my fave hardtail geo)
    Well said, that is becoming increasingly evident. The infinite options and empty optimal truth, adds some excitement to actually riding the beast: 'will it even work'

    From OneSpeed:
    'Looking at your numbers the BB height was the only parameter that stood out as a red flag.' ...

    Yes, too low! Thank you.
    I raised .2" to 12.2 (with 2.35 tires) 63mm drop . Upon reflection, with a dropper post easily able to drop co gravity, there is less loss of benefit. Also, in bikepacking mode , this bike will have 2.25 tres occasionally so that will lower it a tad from the 2.35 tire height.

    My LES is gone, down to the Canyon Dude (scary low N right now). Broke the frame, again, and got amazing $ for the warranty replacement. The Pivot hype paid off.

  16. #16
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    Quote Originally Posted by scottzg View Post

    You've gotten well informed, quality replies from 2 people that are suggesting what i think is nonsense, and a third who isn't offering an opinion... but i'd disagree with him too. Their truth isn't my truth. Taking 5 opinions and smudging them together is stupid. If you want something you can't buy from a production line... strike out on your own. I only suggest you design it with adjustable CS length and room to adjust bar height.
    This is far too cordial. You're supposed to flame, jump up and down while screaming and waiving your hands in the air about what an idiot I am, and all the ways you're right and I'm wrong.

    What are you new around here?

    ** I just realized I measured my BB drop last night with the 120mm fork still on the bike. So it's jacked up a bit higher than it is normally. I don't remember where it sits with the rigid fork. Sorry for the confusion.

    I actually slightly prefer the Transition Vanquish geo (on paper) compared to the Honzo. I haven't had the opportunity to ride one though. Interesting that the BB height is measured as 315mm with a 55mm BB drop. https://www.transitionbikes.com/Bike...VanquishGX.cfm

    Full disclosure- I have a Honzo ST frame ordered for this spring. I'm not sure if I'll build it up right away, but the plan is a 140-150mm fork (Fox 36 ideally) to raise the BB, perhaps an angleset?, and 170 cranks. I've wanted a rowdy hardtail for a while.

    I also have a Surly Krampus set up with a 120mm Manitou Mattoc Pro fork and a 170 dropper. At some point I'll need to stop building steel hardtails, lots of overlap, but I still want to try different configurations. I'm seemingly endlessly curious about geometry.
    Rigid SS 29er
    SS 29+
    Fat Lefty
    SS cyclocross
    Full Sus 29er (Yuck)

    Stop asking how much it weighs and just go ride it.

  17. #17
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    A 29er SS discussion on MTBR? Bringin' it back to Y2K, I love it!

    You could look at it this way:

    Singlespeeds have two modes: climbing, and recovering. They also don't have to account for a given chainline.

    For climbing the thing that matters most is where your bars are relative your pedals for standing power. So you want to get that right and work backwards. For climbing you're not going to loop out with too-short chainstays so we know in this mode we could go short. If this was a dedicated SS you could run the chainline all the way out which would help with the short stay design too. But you want gears so we have some mechanical constraints here.

    For recovering you want something that can go on autopilot while you're seeing stars. So a slack front end and long front center can help you here so you can be lazy with line choice. Short stays aren't going to help you here, so here's an argument to go longer.

    Now we have to wrestle with the argument that shorter stays climb better at low RPMs or not. You don't have the torque of a low gear to spin your wheels, and a longer stay might make rocky climbs a little less jarring. Is there anything else to chainstay length that could help us decide? There is overall weight distribution. If your position is further forwards (say to stay on top of the pedal) then you could shorten the stays, that would help the bike manual.

    BB height - we probably need to go higher, especially if you're running 180s. Since this is a rehash of 20 year old postings, yes, you should run long cranks. Higher center of gravity means more weight shift (squat), which would point towards longer chain stays...

    What's left - seat tube angle? I see two ideas here: one is that you push the seat back as much as you can with your bar position to let you sit back and recover. The other is to go forwards to find a good position for you to spin and tuck. The latter makes more sense in these days of droppers.

    So there's a lot of juggling to do. I can't give you any hard numbers since I don't know you or your trails. Ok, I will say you should run long cranks. I'll give you that one.

    Did I help you design your bike? Probably not.

    Did I relive the MTBR glory years? Oh yeah.

  18. #18
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    Quote Originally Posted by dr.welby View Post

    What's left - seat tube angle? I see two ideas here: one is that you push the seat back as much as you can with your bar position to let you sit back and recover. The other is to go forwards to find a good position for you to spin and tuck. The latter makes more sense in these days of droppers.
    My SS has a slack seat angle (71*). I like it; if i'm climbing something steep i'm already standing. I can stretch out my upper body on the flats. It gives me more room with the saddle dropped an inch, which i frequently do on my SS.

    Not a fan on geared bikes.
    "Things that are complex are not useful, Things that are useful are simple."
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  19. #19
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    My old SS has a 71 degree seat tube too. And 18" chainstays. Despite being "wrong" it was a very fast bike.

  20. #20
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    Despite it being partly theoretical on a SS , I am entirely sold on steep STA for my riding style and terrain. Lots of punchy climbs here in Western MA - either up or down all the time. .. yes, most is standing on the SS , but often you have to sit for recovery and maintaining traction (or rather , proper weight balance between front/rear) with the steep 74 STA sustains energy a good deal.

  21. #21
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    Quote Originally Posted by adinpapa View Post
    Despite it being partly theoretical on a SS , I am entirely sold on steep STA for my riding style and terrain. Lots of punchy climbs here in Western MA - either up or down all the time. .. yes, most is standing on the SS , but often you have to sit for recovery and maintaining traction (or rather , proper weight balance between front/rear) with the steep 74 STA sustains energy a good deal.
    Totally. I'm just enjoying the discussion. On my SS i have to stand on shallower grades than i do on a geared bike, so that transfer from seated to standing happens sooner, so sitting more on top of the rear wheel works awesome.

    Since you can't get a production bike with a long reach and a slack STA, it can be tricky to identify what each attribute is contributing. IMO the reach is the source of the magic, and the STA is mostly a consequence of preserving the cockpit dimensions.


    Welby's 18" chainstays are just crazy-talk though.
    "Things that are complex are not useful, Things that are useful are simple."
    Mikhail Kalashnikov

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