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  1. #1
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    29er Suspension design - XC/Enduro

    Folks,

    While I'm a) Holed up at home after surgery, and b) Not having ridden off-road in a year, I've been looking around at all the new MTB stuff for 2012 just to try and keep my hand and eye, in, as it were.

    As you're all painfully aware I'm sure, the only real option for custom builders is the Ventana rear end kit, which while nice to have, I do feel after taking stock of the market and available technology that straight four-bar designs are one evolutionary rung below VPP based designs.

    My heart has always ironically been with suspension - the first Thylacine was a 4" travel trailbike - so ultimately I've always wanted to do my own frame, but that's really just a pipe-dream.

    So I was wondering, what designs out there do you like at the moment? Do you think there is a market for a 'collective' design / rear end kit, only available to small custom builders?

    What do you think of the 'eccentric' pivot bikes, like the Yeti SB95 and Ibis Ripley?
    No longer member of the bike industry nor society, so don't hassle me.

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    subscribed...

  3. #3
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    I saw that the guy from 18 Bikes is doing a steel single pivot design, which is great. Using the Cast Syntace dropouts too.


    Swingarm by 18bikes, on Flickr
    No longer member of the bike industry nor society, so don't hassle me.

  4. #4
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    Is the difference in axle path worth the extra complication of vpp system over a single pivot design , or is it marketing hype?

    The main problem with simple single pivot designs is the failing shock rate , in the late 90,s this was easily corrected with the use of air sprung dampers which were rising rate but now with Modern air shocks being more linear rate , an extra link is needed to dial in the required rate change ,

    With a 29er wheel having less of a ramp angle than a 26 wheel the additional rearward movement of the axle path achieved by vpp designs may not be necessary ,
    Last edited by ade ward; 02-18-2012 at 01:07 AM. Reason: More info

  5. #5
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    Meh, what's a hinge or two between friends?

    A single pivot is inherently limiting because there is essentially only one variable - its location. More pivots, more tunability.
    No longer member of the bike industry nor society, so don't hassle me.

  6. #6
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    Is that tunability for the builder or the customer,

    Not sure about giving the average customer too much adjustment, is easier to tune something bad than it is to get it right, like the cane creek 4 way damper , too much adjustment for most IMO especially as differences in high speed damping can't be felt by just bouncing on the saddle

  7. #7
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    I've ridden one of the original Outland Research VPP bikes and an Intense Spider. Yes better then any Horst link bike I've ever owned/ridden.

    Tim

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    Quote Originally Posted by TimT View Post
    I've ridden one of the original Outland Research VPP bikes and an Intense Spider. Yes better then any Horst link bike I've ever owned/ridden.

    Tim
    I what way were they better,

    I am not very good at feeling differences between bikes but I could feel the difference between an original single pivot and a single pivot bike with a shock linkage to get a slightly rising rate shock ,
    This was especially felt in dips and compressions as the bike didn't blow through it's travel

  9. #9
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    Quote Originally Posted by ade ward View Post
    I what way were they better, l
    Have you ever gone down a steep hill with a curve/turn at the end? The sharper the curve the more the bike can slide out. Didn't get that feeling on a VPP bike. Felt like the rear tire just stuck and went.Also noticed way less chain slap.

    Tim

  10. #10
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    A lot of it is marketing hype IMO. VPP/Multi-link/etc. bikes pedal well because they create a pivot point that is directly above or slightly behind the bb, and inline with the top of the intended chainring size (or somewhere in between chainrings in the case of bikes disigned to use front deraileurs), when sagged. The more rearward location of the pivot creates a more radical rearward arc, which increases chaingrowth, which increases pedal efficiency (though if you know how to pedal without hopping up and down on the pedals this becomes a whole lot less relevant).These things can be easily achieved with a single pivot design, though some sort of linkage will usually be required to negate a falling leverage rate, as was previously mentioned.

    Also, in linkage designs, the pivot point is constantly moving as the suspension cycles, horizontally for the most part. This creates what some have described as a "dead" feeling. Its because there is not a consistent point in which forces from the rear end are beeing input into the front triangle, and then percieved by the rider at the bb. For some i believe this creates an illusion of increased suppleness, even though the rear end is not doing any better a job absorbing bumps.

    Theres a reason theres still a whole lot of single pivot designs out there. They work just fine, and people still buy them. A lot of people still even prefer them.

    More to come later... need to get some breakfast.

  11. #11
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    A vpp multi link etc would have to be tied to certain points , as even a small change in pivot position can make huge changes to axle path or shock rate, Up to six points

    A linkage driven single pivot design would only require three locations swinging arm , linkage location and shock end eye to make a " kit backend" for frame builders

    I did a design for nukeproof for their scalp dh bike where the bb and pivot was on the same Cnc,d part so ensuring correct positioning and bores parallel to each other
    Last edited by ade ward; 02-18-2012 at 10:36 AM. Reason: More detail

  12. #12
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    Single pivots rock

    Random thoughts:
    -Very few people come to a custom builder for a super-high efficiency full suspension race bike.
    -Single pivots are very, very nice if you want to "customize" the geometry of the rear end (ie, bb height, CS length, main pivot location) without throwing the suspension performance completely out the window. You can't just start randomly moving pivots on a Horst/4-bar/etc setup willy-nilly. With a single pivot (especially low single pivots), things can move around a lot and still work fine.
    -Modern shocks can be tuned to the extent that suspension design is much less important than it used to be.
    -Single pivots don't tend to make noise, break unexpectedly, or require constant maintenance.

    IMHO the only problem with the Ventana kit is that it's a bit porky and a bit expensive. There's no patented/protected technology anywhere on it, so if someone wanted to design a new version with a few tweaks and mass produce it, I'm sure it would be popular.

    -Walt
    Waltworks Custom Bicycles
    Park City, UT USA
    www.waltworks.com
    waltworks.blogspot.com

  13. #13
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    Quote Originally Posted by ade ward View Post
    Is the difference in axle path worth the extra complication of vpp system over a single pivot design , or is it marketing hype?

    The main problem with simple single pivot designs is the failing shock rate
    Re: Axle path. I never hear moto guys complaining about the axle path on their single pivot bikes, damping, chains, pinch flats and can I to un-break their broken forks, but never the axle path.

    I think it makes a difference on mtbs, but the amount it makes a difference seem to be hugely overstated. On a bike with a lot of travel it makes sense to help keep the overall wheelbase consistent and to help stop the rear wheel hanging up on bumps when it's deep in it's travel. But on a bike with 4in or less I can't see how you can get a useful amount of rearward travel without either using two chains or have a silly amount of pedal feedback.

    Re: Single pivots.

    I may be being dense here, but to me a falling leverage ratio is exactly what a bike should have. That way the ride is soft at the top, but ramps up the deeper into the travel you go. A big advantage of simple single pivots (to me) is that they tend to do that in a very linear manner without any sudden ramp ups or drop.
    My favourite thing about my Prophet is how it 'catches' you on landing from a drop, as opposed to simply blowing through it's travel. I nearly had a MK1 Nomad instead of the Prophet, but the way it would suddenly drop through the middle of it's travel like I'd hit a massive rock put me right off.

  14. #14
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    ^^^I think you're describing a rising rate shock. With a falling rate shock, it's initially stiff, then gets plusher as you go through the travel. IOW:

    Rising rate: the first inch of shock travel moves the wheel more than the last inch
    Falling rate: the first inch of shock travel moves the wheel less than the last inch.

    Or do I have it backwards? I can't tell right now since I'm tired from skiing and having a beer.

    I'll add one thought that I've mentioned here at some point in the past: I think it would be cool for components of a ventana style rear end (i.e. dropouts, pivots, yoke(s), rockers) that the builder welds/brazes together with choice of tubes.

  15. #15
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    Quote Originally Posted by Walt View Post
    -Very few people come to a custom builder for a super-high efficiency full suspension race bike.
    -Single pivots are very, very nice if you want to "customize" the geometry of the rear end (ie, bb height, CS length, main pivot location) without throwing the suspension performance completely out the window. You can't just start randomly moving pivots on a Horst/4-bar/etc setup willy-nilly. With a single pivot (especially low single pivots), things can move around a lot and still work fine.
    -Modern shocks can be tuned to the extent that suspension design is much less important than it used to be.
    -Single pivots don't tend to make noise, break unexpectedly, or require constant maintenance.

    IMHO the only problem with the Ventana kit is that it's a bit porky and a bit expensive. There's no patented/protected technology anywhere on it, so if someone wanted to design a new version with a few tweaks and mass produce it, I'm sure it would be popular.

    -Walt
    I kinda think that there is an emerging untapped market for performance full-suspension bikes - we're just not exploiting it.

    There's a couple of points here.

    Firstly, when I looked into licencing a rear end (ha) a couple of years ago as a point of difference to the Ventanas, the cost of the chainstay/seatstay parts were USD275, mill finish. Rockers and all pivots added USD114, making a raw cost of USD389. I can't remember how much OE shocks are, but I think about USD80? I guess everyone is getting the picture.

    Secondly, I'm sure everyone recalls the "Aluminium is great because it's cheap to machine and easy to manipulate blah blah blah" conversation as it pertains to full suspension frames, but do you realise 'modern' Aluminium 29er trailbike frames weigh on average 6.5lbs (3kgs)?!

    Dunno about you, but a heavy, large size 29er hardtail in STEEL weighs circa 2kg, so add 200g for a shock, and that leaves you with 800g worth of links and reinforcement? Seriously?

    Steel is real fellas, come oooooooon!

    No longer member of the bike industry nor society, so don't hassle me.

  16. #16
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    I think I like the idea of the Santa Cruz Nickel frame - single pivot with a modified shock rate linkage.



    As a 29er, of course.

    Seriously, if something like this couldn't be built in steel under 6lbs (and even less in Ti) then there's something wrong.

    The only thing I don't like about the design - for customisation - is the fact that it would be much better if the top and downtube were largely free from pivot points.
    No longer member of the bike industry nor society, so don't hassle me.

  17. #17
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    sorry to interrupt, especially as a lurker and non-framebuilder, but there used to be another option, but since Maverick has gone out of business, i'm not sure of anything similar.

    Seven made a beautiful frame around the jack-shaft style suspension system. this example happens to be my dad's

    ok, back to lurking. keep up the good work, all!
    Attached Images Attached Images

  18. #18
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    Small Canadian builder Xprezo is doing a mixed material frame. Front triangle is aluminium and the rear out of steel.

    I have a couple rides on my new Super-D and really really like it.

    CYCLES XPREZO - SUPER-D - FR



    The frame is 2633g with shock. Pretty good weight for a 145mm travel bike.

  19. #19
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    Steel for the rear triangle and they still couldn't get the chain stays under 17"?

    Good weight though.
    No longer member of the bike industry nor society, so don't hassle me.

  20. #20
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    Quote Originally Posted by Thylacine View Post
    Steel for the rear triangle and they still couldn't get the chain stays under 17"?
    Regardless to what you read on the internet life does not revolve around chainstays shorter than 17".

    They likely could have gone shorter but 17" is pretty spot on for a fs of this nature.

  21. #21
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    My last bike had 17.75" chainstays, but thanks for wording me up on what the Internet says.
    No longer member of the bike industry nor society, so don't hassle me.

  22. #22
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    How about a "plug and play" carbon rear end? They have special carbon chain and seat stays for road bikes, how about a standard rear end where the main variable are the pivot points and amount of travel?
    PVD, your next project? How about a "tele-lever" soft tail?
    Hope your are feeling better...

  23. #23
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    I did a lot of the detail work on the nukeproof scalp dh bike , this is a single pivot with a linkage driven shock

    What I tried to do was to make a single part with bb swinging arm pivot and linkage bearing all machined together
    So all three major points are in the same plane and at distances , infact in production the linkage pivot was welded to the top of the I beam seat tube part but all machining was done together

    Certainly an investment cast bb with bb and swinging arm pivot on would be a good start

  24. #24
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    Sorry trying to find a pic of the scalp to link to but have failed

    spr bikeclub: We all live in the YELLOW submarine!

  25. #25
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    What ever happened to this. Split Pivot Suspension - Ride for fun.

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