youve heard it before - long, slow, slack, steep- Mtbr.com
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  1. #1
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    youve heard it before - long, slow, slack, steep

    i build myself a 'progressive' hardtail for riding in the pnw. its got around 700 km on it now.

    unsagged geo
    reach - 515
    stack - 630
    hta - 62.5
    sta - 77
    bb drop - 69
    chainstays = 435-450

    important parts numbers
    stem - 50
    bars - 760
    tires - 29x2.6
    travel - 140

    me
    hight - 5 11
    wing span 6 2

    reasoning
    reach/stack - longer is always better, right? i built the stack too low, and ended up running 25mm of spacers under the stem reducing the reach to 500ish mm. next time, more stack to keep the intended reach.
    hta - its slack. feels great down hill. The wheelbase can get hung up on flat lumpy trails.
    travel - i wanted the geo to stay as consistent as possible through out the travel. something like the doctahawk at 170 mm up would change to 8.5 degrees.
    bb drop - how low is too low? im not sure yet. sure, i hit my cranks while climbing pnw tech-jank, but the lowness feels great in corners.
    chainstays - short chainstays suck for going fast. ive riden bikes with short chains (ex - rootdown 415) and have never been blown away by them. they dont instill confidence at speed on the rough stuff like long stays do. i usually ride this bike in the 440 zone.
    stem - sup with short stems? ive tried 32 mm and 40 mm stems with mixed results, how you going to keep the front tire loaded with a short stem? i plan to experiment more with this.

    my next project is a single pivot dual susp with simular geo.



    Attached Thumbnails Attached Thumbnails youve heard it before - long, slow, slack, steep-img_2091.jpg  

    Last edited by wzrd.; 05-24-2020 at 09:09 AM.

  2. #2
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    Your picture doesn't work

    From a design perspective reach/stack isn't all that useful. It's more helpful to look at cockpit length and bar drop, and front-center.

    That bike looks like it fits big. Do you have the bars above the saddle? How hard is it to get the front wheel up?

    Agreed on short chainstays. Never get along with them.
    "Things that are complex are not useful, Things that are useful are simple."
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  3. #3
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    thanks for the heads up on the image, edited the original post.

    bars are below the saddle, and i havent noticed any issues manualing or hoping it. the bike seems to have a large 'sweet spot' for manuals/catwalks once the front wheel is off the ground too.

  4. #4
    pvd
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    It's a lot easier to show a print than the random number list. Also, we show hardtails with the fork sagged. I like 30%, your mileage may vary.

    I'm 5'10 in NorCal. Very different than PNW where you can get away with those steep seat angles and more slack head tubes. Still, the head tube is probably too slack. If you focus on the handlebar problem, you can make it steeper and have the front end work better. Probably better to work on this than an FS bike with the same problem. I don't like going below 65 degrees around here. I'm sure 64.1 degrees can work in PNW but it would still suck in lots of conditions.

    Those chainstays are very very long. That's a marketing thing. Getting them down to 415-425 would be a lot nicer. I can't imagine that your analysis of longer chainstays is correct, might try sorting the rest of the bike out to find out.

    Your handlebars are 48mm further forward and about 8mm higher than mine and that could be giving you that sketchy feeling. I know that that would freak me out on the slopes. This is significant.

    Also, if it's a bike for PNW, why such a tiny fork? A 180mm fork works well in NorCal. I don't think that that would change for PNW.

    Note that my bike is:

    I don't make bicycles. I make weapons systems. | Peter Verdone Designs



    I had to try to draw your geometry just to make sense of it. That seat tube is so nuts. 79.3 degrees of torture, that would leave strong men dead in NorCal.

    The front center is 7mm shorter than mine and you could go a little longer..

    Last edited by pvd; 05-25-2020 at 12:29 PM.

  5. #5
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    Quote Originally Posted by wzrd. View Post
    thanks for the heads up on the image, edited the original post.

    bars are below the saddle, and i havent noticed any issues manualing or hoping it. the bike seems to have a large 'sweet spot' for manuals/catwalks once the front wheel is off the ground too.
    Your height, saddle height, and wingspan are interesting. Looks like you have a remarkably short torso and super long limbs. Like <1% of the population rangey. Good on you for going your own direction with your frame.

    Quote Originally Posted by pvd View Post
    Also, we show hardtails with the fork sagged. I like 30%, your mileage may vary.
    Geo with fork sagged is some dumb shit. Measure from sag and you'll confuse fork behavior, rider behavior, and geo behavior. How the bike behaves at topout and bottomed are important, and that dynamic behavior in between is subjective and depends on rider instincts and fork tune. Worthless if you're designing for someone else.

    It has the same problem as your first interpretation of pvd-rad; good idea, but without solid baseline measurements... garbage in- garbage out. The new iteration with the broomstick is MUCH better, but you're still looking at a 3d joint with a 2d measurement. Hard to translate fit from one person to another.
    "Things that are complex are not useful, Things that are useful are simple."
    Mikhail Kalashnikov

  6. #6
    pvd
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    You just explained EXACTLY why we use sagged geometry to communicate the bike. Between topped out and bottomed out is JRA. That's the 'average' condition the rider will experience.

  7. #7
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    Quote Originally Posted by pvd View Post

    Those chainstays are very very long. That's a marketing thing. Getting them down to 415-425 would be a lot nicer. I can't imagine that your analysis of longer chainstays is correct, might try sorting the rest of the bike out to find out.

    Your handlebars are 20mm further forward and about 25mm lower than mine and that could be giving you that sketchy feeling. I know that that would freak me out on the slopes.

    Also, if it's a bike for PNW, why such a tiny fork? A 180mm fork works well in NorCal. I don't think that that would change for PNW.
    i believe that the chainstays should grow with the front center. if i were to build a bike for someone shorter, the chainstays would proportionally shorten.

    i agree that the bars could be taller, and this is something im playing with.

    i truly dont see the need for long travel forks on hardtails. even when riding aggressively on rowdy trail, i havent wished for more travel.

    unfortunately the free bikecad doesn't have quite as many measurements. here is an unsagged drawing.

    youve heard it before - long, slow, slack, steep-wzrdv2.2.jpg

  8. #8
    pvd
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    Pay up, sucker. You just found out how much 'free' has cost you.

    I gave you feedback based on a very different level of understanding (clearly). Feel free to ignore it.

  9. #9
    pvd
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    FYI, your fork is drawn incorrectly in that print.

  10. #10
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    Wzrd:
    Cool! Awesome that you went for some properly modern geo. It's interesting to hear your feedback.

    I've been riding several prototypes recently with similar geometry and my thoughts are as follows:

    Front center: I'm 6' and currently riding 825 FC and it just doesn't feel very long at all. I think I could add at least another 25mm and still love it. I haven't felt that it's too long even on pretty steep switchbacks and in tight stuff.

    Chainstays: I'm still not positive about these. On the hardtail, I love my chainstays short, but not too short. I've found a happy medium in right around 420 effective (usually 417 actual or so). But on the full suspension, I'm running 444 and it almost never feels too long. Bringing that weight balance further forward just by that much makes cornering completely different. I don't have to lean as far forward to weight the front wheel while cornering, and it means I have more flexibility to move around the cockpit as terrain changes. I'm going to do more riding with my hardtail's dropouts slid all the way back and try to compare.

    STA: The dually I'm on right now has the steepest STA I've built for myself to date, and with a 150 fork it was running at 78 degrees. My thoughts are this: STA is VERY subjective to where you ride. On our in town trails which aren't very steep and fairly chill, a STA of more like 74.5 works fine. As soon as you get into the mid country and high country riding around here, that 78 STA was absolutely incredible. I swapped forks and it went down to 77 degrees, and for my long ride yesterday I wanted it steeper. I'm thinking 76 - 78 is perfect at least around here. The only time it feels off is when you're riding really long flats, but we just don't get any of that around here. One thing I noticed about that steep STA is just how much it raised my saddle position. It wasn't too bad, but I don't like running much drop to my bars, so I'm going to lengthen the head tube on the next one.

    Interested to see your dually, post it up when you've built it!
    Myth Cycles handbuilt bike frames
    Durango, CO
    http://www.mythcycles.com

  11. #11
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    Quote Originally Posted by pvd View Post
    Pay up, sucker. You just found out how much 'free' has cost you.

    I gave you feedback based on a very different level of understanding (clearly). Feel free to ignore it.
    Hmmmm. You sir, win the interwebz arrogance award, not for the day, week, or even month. I'm thinking more the year.

  12. #12
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    Quote Originally Posted by Erichimedes View Post
    . My thoughts are this: STA is VERY subjective to where you ride. On our in town trails which aren't very steep and fairly chill, a STA of more like 74.5 works fine. As soon as you get into the mid country and high country riding around here, that 78 STA was absolutely incredible. I swapped forks and it went down to 77 degrees, and for my long ride yesterday I wanted it steeper. I'm thinking 76 - 78 is perfect at least around here. The only time it feels off is when you're riding really long flats, but we just don't get any of that around here. One thing I noticed about that steep STA is just how much it raised my saddle position. It wasn't too bad, but I don't like running much drop to my bars, so I'm going to lengthen the head tube on the next one.
    This is where looking at sagged numbers really makes a difference. On a full suspension bike the sta under rider sag can be greatly affected. I always keep an eye on how a frame is looking under rider sag as that is how it will be ridden, especially if itís a frame for myself.

    Erichimedes any idea what your sta is on flat ground with front and rear sag?


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    Quote Originally Posted by Little_twin View Post
    Erichimedes any idea what your sta is on flat ground with front and rear sag?
    I've been setting up my front and rear to have the same sag, so that's where the STA should be 77.

    As for what it is while actually climbing up something? Very hard to quantify, since it can be very fluid depending on a lot of factors. I do notice a change when I set my shock to be locked out, as it usually goes higher in the travel and stays there during even steeper sections.
    Myth Cycles handbuilt bike frames
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  14. #14
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    youve heard it before - long, slow, slack, steep

    Quote Originally Posted by Erichimedes View Post
    I've been setting up my front and rear to have the same sag, so that's where the STA should be 77.

    As for what it is while actually climbing up something? Very hard to quantify, since it can be very fluid depending on a lot of factors. I do notice a change when I set my shock to be locked out, as it usually goes higher in the travel and stays there during even steeper sections.


    Interesting. So are you measuring sag as vertical axle travel front and rear compared to the more typical mtb method of measuring a percentage of your available shock and fork stroke?


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  15. #15
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    Quote Originally Posted by Little_twin View Post
    Interesting. So are you measuring sag as vertical axle travel front and rear compared to the more typical mtb method of measuring a percentage of your available shock and fork stroke?
    Ah, I get what you mean. Yes, in that statement, I was just referring to the fact that I've got it set up so the geo stays roughly the same when I get on it. For no particular reason, I've just got it going that way.

    Front is at 160, with 30% sag, and rear is 145 with 25% sag, so about 5mm difference. If you include fork flex, it's more like 2 or 3. So probably not exactly 77, but in that neighborhood. I guess I was oversimplifying for the sake of conversation.
    Myth Cycles handbuilt bike frames
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    http://www.mythcycles.com

  16. #16
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    Quote Originally Posted by Erichimedes View Post
    Ah, I get what you mean. Yes, in that statement, I was just referring to the fact that I've got it set up so the geo stays roughly the same when I get on it. For no particular reason, I've just got it going that way.

    Front is at 160, with 30% sag, and rear is 145 with 25% sag, so about 5mm difference. If you include fork flex, it's more like 2 or 3. So probably not exactly 77, but in that neighborhood. I guess I was oversimplifying for the sake of conversation.
    Iíd be curious what happens to it when you climb. Seat tube angle is one of those things that is so different from person to person, and location to location. On my full suspension bike I donít mind and actually prefer around a 76 but I know I run the rear soft compared to the front and it slacks out when riding. On my xc bike I can tolerate 74-75 but itís made for one thing and comfort is not it. On my everyday hardtail Iíve settled on 73.5 as my knees seem to tolerate that for indefinite amounts of time and doesnít seem to negatively affect my climbing performance.


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