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  1. #1
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    Geometry discussion

    Wondering what y'all think of THIS.

    The video is nearly the same as the text if you don't like reading.

  2. #2
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    I guess I don't understand what the word "balanced" means.

  3. #3
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    Before we hear about everyone's expert opinion I would say it would be interesting to ride and see how it feels.


    It seems bikes these days are focused more and more on the downhill. (In full curmudgeon mode now...)

    I've always been more into steeper geometry and and feel it is just as important to be able to manuver through rock gardens going slow and uphill, as it is to be able to blast over stuff going down.

    But I probably need to ride a few more bikes to get an accurate opinion of what is best for me at this point in my life.

  4. #4
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    Hey;

    I agree completely with the geometry portion (that was all I read, with my short attention span). I think that Walt might be able to point to this as more proof of his bedrock Front-Center-is-King argument. I was a bit puzzled by the concept at first, but I have learned that I agree with him. This is coming from someone who never had a bike really fit until I made my own.

    My Niner RIP9 was a godsend to me when I first threw a leg over it. It was my first 29er, but was the first bike actually built to be EXTRA large for extra large people. I used its numbers as a partial basis for my Fatties, actually extending both the WB and FC even more. I currently use a 110mm stem on the Niner, and the position is very upright. By comparison, on my Fatties, I am using a 100mm stem, which on them gives me a fairly aggressive stretched position. Now, my Niner almost feels like the bars are in my lap by comparison. Almost. My Fatties are the first bikes that I can really stand tall and crank on without feeling like my nose is in front of the axle!

    Buying off the shelf bikes that really fit has always been a compromise, and stem length has been a classic way of getting around that for folks not having a custom bike built to REALLY fit. I would think that we might all agree (or at least consider) that using a stem to dial in rider fit is variously less than ideal, in the abstract, especially if it got much longer than 100mm to seal the deal. Still, within reason, it is just as viable as any other tuning tool. Where I think Kona may have erred is in offering a stem so short that they limit the range of adjustability there, only allowing longer but not shorter.

    Still, in the end, I think they are on to something, if not something new. Don't look at the stem length... or even the dreaded effective TT length. They are a red herring. Go out and ride, and see where your nose is in relation to the front axle. That is a better means of judging fit in my estimation, and having room there will certainly improve downhilling, somewhat regardless of HT angles and such. Get a reasonable length stem that works, after that fact.

    YMMV.
    Most people ply the Well Trodden Path. A few seek a different way, and leave a Trail behind.
    - John Hajny, a.k.a. TrailMaker

  5. #5
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    Where I think Kona may have erred is in offering a stem so short that they limit the range of adjustability there, only allowing longer but not shorter.
    Good point.

  6. #6
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    Personally, I much more enjoy wresting a slack-long front center bike up hill, than nursing a steep-short front center bike down the hill.

  7. #7
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    Interesting.

    My first MTB build of recent times was where I constructed a frame that copied a Kona Kilauea of early '90's vintage, but I added 40mm to the top bar as it was way too short for the rider in question. This lengthened the F/C by quite a bit. It acheived all that this article is suggesting, but the most important thing was that the rider was able to ride the bike properly.

    The second area of comment, is the short stem. If you are a user of the Mary-Bar style, and I am one of those, of sorts, you have the option of placing your hands out wide and near the pivot centre for quick steer/leverage, and hands closer to the stem giving a longer stem effect, and better straight line stretch.

    I don't think that these concepts are as radical as claimed, and I would venture to suggest that from many of the recent builds that I have seen recently on this forum in the drawings rendered are tracking this way without knowing what the Manufacturers are doing. More to the point guy's, we're doing it right.

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

  8. #8
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    I suspect the recent trend to what would have seemed like ridiculously slack front ends a few years ago is being aided by:

    - AM frames with short rear ends and long front centers, which takes weight off the front wheel reducing wheel flop
    - Wider and wider bars

    There's also larger fork offsets, though that seems to be offset by larger wheels.

  9. #9
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    Quote Originally Posted by TrailMaker View Post
    I would think that we might all agree (or at least consider) that using a stem to dial in rider fit is variously less than ideal, in the abstract, especially if it got much longer than 100mm to seal the deal.
    I don't know - my arms are 2" longer than average, so I'm not sure if I really want to push the front center out 2" just so I can run the same length stem as everyone else who isn't built like an orangutan.

  10. #10
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    Quote Originally Posted by dr.welby View Post
    I suspect the recent trend to what would have seemed like ridiculously slack front ends a few years ago is being aided by:

    - AM frames with short rear ends and long front centers, which takes weight off the front wheel reducing wheel flop
    Good point. I hadn't thought about how wheel flop is related to weight on the front. But on the rear, I doubt that chainstay length has decreased very much (as Kona claims in the video). Short chainstays have been a design goal forever, and there really isn't much room to go from where they have been.

  11. #11
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    Sounds like how I like my bikes to ride.

    Who was it that said something like "build what you want, and then come up with some ******** to sell it"?

  12. #12
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    Quote Originally Posted by adarn View Post
    Sounds like how I like my bikes to ride.

    Who was it that said something like "build what you want, and then come up with some ******** to sell it"?
    Dave Weagle?


  13. #13
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    I think Kona is on point here. I also think they are doing a really good job of promoting themselves. I would love to see more videos like this.

  14. #14
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    I'm sure most bigger bike companies think a lot about geometry and Kona seems to be trying to share that they are expanding on old ideas and talking about it to potential customers (marketing). Only helps to educate people on the complexity of the situation. I like that they brought up front center, something hardly any normal rider has heard of. But it seems like they are using effective top tube length and front center almost interchangeably. The guy kinda throws out a lot of stuff and jumbles it up a couple of times IMO, kinda confusing. I'm not an expert but here's some things I noticed.

    I like how they compensate for the increased wheelbase by shortening the chainstays a bit (because they lengthened the top tube and also the front center). They didn't shorten the chainstays that much though, only some millimeters, like smilinsteve said. But what this does for 'balancing' the rider over the wheels is up for debate. The front-centers on these bikes are very big. This gets at a previous post I started about longer travel 29ers with slackass head tubes and shortass chainstays. The front center values on the Konas are WAY higher than normal and what Walt, PVD and others have stated are best for them. From Kona's website they range from 696 for the smallest frame size to 772 for the biggest frame size (the new Process 111 29er). Chainstay length for this model is 430. Not super short, maybe it is for rear suspension, don't know.

    What gets me is saying there's a 'right' weight distribution on a stock frame size and saying in the same sentence that a one-size-fits-all 60mm stem is the way to achieve that. Also that a shorter stem is less flexy than a longer 70mm stem. I mean seriously...60-70mm has a noticeably different flex...?

    I completely understand what they're going for -- a bike that's stable at speed yet still somewhat maneuverable in tight singletrack and switchbacks and still climbs well. Whether this geometry pulls that off i don't know, haven't ridden it, but I'm sure they're really fun on that downhill "all-mountain" terrain with just slamming through rough trails with high speed stability. I can pretty much guarantee that they'd suck to climb on though, or do anything else than push uphill and bomb downhill. And since when did "All Mountain" mean shuttling or hiking uphill? But hey, i like to ride uphill too so I'm the wrong guy to ask.

  15. #15
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    Kona is using very short rear ends on these bikes, as in under 17".

    Process 134 and 153 = 425
    Process 111 = 430

  16. #16
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    I guess i consider short chainstays to be 420 or less now. But that's for 29er hardtails.

    In 2008 Trek's 26er dualies had CS length under 17" (426, 424). The 69er hardtail had a 421mm.
    So what's new exactly that Kona is doing? To me it's mostly short stems and longer front centers which really all it does is put the rider's weight more over the rear wheel so it seems easier to go faster and rail stuff. But that front axle is way out there...

  17. #17
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    Quote Originally Posted by Meriwether View Post
    To me it's mostly short stems and longer front centers which really all it does is put the rider's weight more over the rear wheel so it seems easier to go faster and rail stuff. But that front axle is way out there...
    That is the key point right there. For a certain type of rider, in a certain type of terrain, this is key. For others, meh. Going faster and railing stuff is why some people ride.

  18. #18
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    Whit,

    Yea, when I said I think they are on point I'm saying that they are talking about mtn bike geometry in the right context IMHO. But I agree the devil is in the details. I will say I personally like bikes with a higher front center when the HT is slack. I ride a bit more forward on a bike though, so I like that feeling of the front wheel out in front of me. Gives me more confidence going down and cornering. I think when someone values climbing performance that FC number has gotta come down naturally. That being said I think Kona is selling these bikes to riders that care more about going down and might enter an "enduro" or something. Which is basically a downhill race from the late 90's with stages. :-)

  19. #19
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    Agreed, but what's the tradoff is my point? Are you saying that you can't go as fast without a bike like this? No, i don't think you are, so is the trade-off of how it climbs and wheel-flops at slow speed, steers and tracks at slow speed downhill corners, and rides the rest of the 'mountain' worth it? I'm not sure. So I'll have to build a similar geometry up and try it for myself.

  20. #20
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    A lot of enduros are run on current DH tracks (see Winter Park). Bikes like this would be overkill on DH runs from the 90's.

    I've ridden bikes like this all over, and yes they take much different technique to turn at lower speeds, but most people riding these bikes don't care about that stuff. And usually aren't afraid to slide the rear end around when need, or get off and push up a steep pitch.

    There are plenty of middle of the road bikes that will be better all arounders, but Kona isn't going for that.

  21. #21
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    agreed and well put.
    Will be fun to give it a go.

  22. #22
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    Quote Originally Posted by eMcK View Post
    Kona is using very short rear ends on these bikes, as in under 17".

    Process 134 and 153 = 425
    Process 111 = 430
    No different than SC Blur TR. 16.9 inches.

  23. #23
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    Quote Originally Posted by Meriwether View Post
    so is the trade-off of how it climbs and wheel-flops at slow speed, steers and tracks at slow speed downhill corners, and rides the rest of the 'mountain' worth it?
    The other issue I suspect is that the front end would be very light on climbs, limiting how steep you could go before front wheel lift, especially if rocky.

  24. #24
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    Quote Originally Posted by Meriwether View Post
    I guess i consider short chainstays to be 420 or less now. But that's for 29er hardtails.
    Who makes that? Do they have to curve the seat tube?

  25. #25
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    eMcK, yea agree. They would be overkill. I guess in the end it comes down to where do you want to compromise and where do you want to optimize. All depends on the rider / terrain. You just can't have too many bikes.

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