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Added a comment about photo WINNING BIKE: Gee Atherton's World Champs GT Fury 27.5 9/8/2014 5:05 AM
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It will be very interesting to see precisely what the geometry of this bike is when the Atherton replicas emerge. Top level DH racers will generally want a bike they can win on. On the evidence, the changes GT have made during the season have resulted in a better race bike.

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This photo has 7 comments.

Added a comment about feature First Look: Radical New 2015 Specialized S-Works Demo Carbon 8/30/2014 9:51 AM
C50

@boomslang Well, thank you for your informative comment. I'm sure that there is a lot there of general relevance for DH bike frame design and construction. You wouldn't be too shocked to learn that there are those of us who continue to consider the older frame design to be the better one overall. So, I welcome the news - widely reported and I hope reliable - that a 27.5in version of that bike will continue to be available in aluminium.

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This feature has 52 comments.

Added a comment about feature First Look: Radical New 2015 Specialized S-Works Demo Carbon 8/29/2014 2:51 PM
C50

@boomslang I am very interested in what you have said. You seem to have an intimate knowledge of the new Demo. Are you connected with the Demo design group or are you researching this in some other capacity?

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This feature has 52 comments.

Added a comment about feature First Look: Radical New 2015 Specialized S-Works Demo Carbon 8/29/2014 2:25 PM
C50

A good analysis by Antonio Osuna of the 2015 Demo kinematics has been published at http://linkagedesign.blogspot.com.es/2014/08/specialized-demo-2015.html.

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Added a comment about feature New Rocky Mountain Flatline Nearing Production? 8/19/2014 2:36 AM
C50

My explanation probably could have been better. The point is that a rising (or upward sloping) anti-rise curve (to see what a rising AR curve (or graph) looks like go to http://linkagedesign.blogspot.com.es/2014/08/transition-patrol-275-2015.html - the Transition bike, while it has less travel than the RM prototype uses a similar linkage design and would exhibit similar pedaling and braking characteristics) is considered by many able designers to result in good traction while braking. Almost all suspension bikes designed by Dave Weagle, Specialized and Trek use a rising AR curve. Go to http://www.i-tracksuspension.com/suspensiontheory.html for an account that sets out the supposed benefits of a rising AR curve.

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This feature has 7 comments.

Added a comment about feature New Rocky Mountain Flatline Nearing Production? 8/18/2014 11:13 AM
C50

Recently, horst-link and split pivot designers have been implementing designs that allow for more heavily manipulated anti-rise curves that partially govern suspension behaviour while braking e.g. the new Ghost and Transition trail bikes as well as the new Salsa split pivots and the Devinci Spartan. This bike will have a lot in common with that design approach - the rearward slope of the rocker link is the clue. Expect RM to make lots of claims about braking traction. The traction benefits of this or that suspension parameter are hard to prove but many good designers seem to consider the rising AR curve that results from appropriately positioned linkage pivots to be good for braking performance.

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This feature has 7 comments.

Added a comment about feature First Look: Radical New 2015 Specialized S-Works Demo Carbon 8/14/2014 8:32 AM
C50

Two articles, one on this site (http://www.vitalmtb.com/product/feature/Details-Unveiled-First-Look-2015-Specialiized-Demo-Carbon-650b,276) and one elsewhere (http://www.pinkbike.com/news/specialized-demo-2015-troy-brosnan-tech.html) confirm the substance of my earlier comments - things I supposedly couldn't know according to some. (note: I am not saying these writers share my opinions about the new Demo, they don't, only that they give the same account of the facts about the kinematics and structural features of the bike.)

This siite - http://linkagedesign.blogspot.com.es - helps give genuine information about how the linkages of real bikes work. You can know plenty about how a bike rides without riding it. The alternative is to believe the fields of design and engineering are a waste of time.

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This feature has 52 comments.

Added a comment about feature First Look: Radical New 2015 Specialized S-Works Demo Carbon 7/30/2014 10:08 PM
C50

By the way, I didn't determine anything from watching the video. I used the geometric method of calculating anti-squat and anti-rise from the perfectly good photograph on this page. I had already looked at the dynamics of this sort of linkage from an emulation I tinkered with in the Linkage program quite some time ago. As it happens there is now a carefully developed emulation of the new Demo by Kryatof Jetmar that sits permanently in the public domain library of Linkage and it confirms the points I made about the new linkage function, although while the new bike is more pedaling neutral the improvement is modest rather than great. With the new details that are available our understanding of how the suspension functions will get more accurate but the general picture is already clear.

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This feature has 52 comments.

Added a comment about feature First Look: Radical New 2015 Specialized S-Works Demo Carbon 7/30/2014 2:37 PM
C50

There is nothing arrogant in my comments. It has all been common design practice up until now. Look closely at the image you have made reference to. Imagine pulling the axle out and moving your arm forward in the open space between the two sides of the (multi-part) swingarm. You arm will go past two sets of pivots without cross bracing between the drive and non-drive sides before being obstructed by any sort of structure that joins the two sides of the swingarm. There would be very few bikes like that out there. That is because t is not a good idea to have too many pivots in the suspension linkage without proper cross bracing to create a stiff or flex free structure. Dual short link bikes commonly use full width pivot axles and Horst-links have always had a single piece seatstay that braces the seatstay/rocker pivot very effectively. Without much flex elsewhere and with the rear wheel axle also binding things together the unbraced chainstay pivot of the horst-link has worked well, without much flex, in practice. That you can move your arm around freely in this big void between the two sides of the swingarm of the new bike without finding any cross bracing near either of the mentioned pivots means that Specialized has thrown out the rulebook that everybody previously used. The point I have made is old school. From my standpoint (and I would say the standpoint of prevailing engineering practice) Specialized is violating a basic rule. No doubt, they would say, carbon changes everything.

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This feature has 52 comments.

Added a comment about feature First Look: Radical New 2015 Specialized S-Works Demo Carbon 7/30/2014 12:37 PM
C50

The Yeti DH9 has been thoroughly analysed by Antonio Osuna (see http://linkagedesign.blogspot.com.es/2013/02/yeti-dh-9-2004-old-school.html) who notes the big difference that the little floating carrier makes. You are completely right about the carrier being crucial to the good braking performance of the Yeti and other similar bikes.

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This feature has 52 comments.

Added a comment about feature First Look: Radical New 2015 Specialized S-Works Demo Carbon 7/30/2014 12:11 PM
C50

Sorry, my post was a bit of a moving target - ill considered expression, my bad. You were posting as I was editing. I was very interested to read your post though.

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This feature has 52 comments.

Added a comment about feature First Look: Radical New 2015 Specialized S-Works Demo Carbon 7/30/2014 11:51 AM
C50

Yes, the suspension linkage on this bike has more in common with the Lawwill link than it does with Specialized's own expired Horst-link patent. "FSR" is by now little more than a marketing term.

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This feature has 52 comments.

Added a comment about feature First Look: Radical New 2015 Specialized S-Works Demo Carbon 7/30/2014 12:54 AM
C50

I emulated the new linkage using a modified version of the publicly available Status linkage geometry in the library of bikes that comes with the Linkage program. That is not an exact method but the speculation in my comments is well informed speculation.

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This feature has 52 comments.

Added a comment about feature First Look: Radical New 2015 Specialized S-Works Demo Carbon 7/29/2014 7:43 PM
C50

Besides the carbon artistry what is new is the linkage. With any linkage what you are concerned with are its structural and functional - wheel path and kinematics primarily - characteristics. So how does this new bike rate on that scorecard.

Wheel path and pedal feedback - not too dissimilar to the old bike (probably)
Anti-squat - the new bike is greatly improved (i.e. more pedaling neutral)
Anti-rise - braking will be different on the new bike but AR will continue to be low which is generally considered to be good for traction when braking
Leverage rate - that was alright on the old bike, the new one won't radically deviate

There is nothing wrong with or especially notable about these functional changes. The same result was readily achievable with relatively small changes to linkage pivot positions on the existing bike. Where the new bike is let down is in the structural characteristics of the rear end. The rear axle is mounted on two separate linkage pieces on each side of the wheel - the single rear end seatstay component that the wheel mounts to, common to all Horst-link bikes, is gone. These separate pieces on either side of the wheel join to the other linkage bars via a couple of pivots within the circumference of the wheel (looked at in side view). In general full width pivot axles are better than aligned pivots on either side of the wheel and if aligned pivots are used it is important that they are near a structural member bracing drive and non-drive sides together.

I am not impressed by the new design - it appears to be prone to flex. To what extent that concern will manifest itself, is hard to say. Just how noticeable flex becomes will depend on the quality of the pivots, bearings and carbon structures used.

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This feature has 52 comments.

Added a comment about feature Vital Power Rankings - Fort William, Scotland World Cup - The 15 Fastest Racers Going In 6/5/2014 8:07 AM
C50

I completely agree. Mulally has been oustanding. Mulally, Bryceland and Bruni, all relatively young guys look to be showing vast improvement this year. Without doubt, they are contenders.

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This feature has 17 comments.

Added a comment about news blog Judge Rules Trek's ABP Design Does Not Infringe on DW's Split Pivot Patent 12/17/2013 7:44 PM
C50

Oh, by the way, I recommend reading @Varaxis comments on the particular patents below. Its as good an effort as I have seen to survey this tricky (and sometimes nearly impenetrable) territory.

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This news blog has 12 comments.

Added a comment about news blog Judge Rules Trek's ABP Design Does Not Infringe on DW's Split Pivot Patent 12/17/2013 7:32 PM
C50

I agree with some of the sentiments expressed by @prestondh. Concentric pivots (not a new idea) at the rear axle dropouts of a bike (also not a new idea) should not be patentable. However, the known history of DW's dealings with Trek prior to the APB patent being filed is really much more in line with DW's presentation of the facts. It is very unlikely that the inspiration to the creation of APB came from anywhere else than DW's presentation of the concept and the design to Trek when he tried to sell his design services to them, well before APB existed.

There are some aspects of the judge's findings that are troubling. The emphasis on shocks and leverage rates makes it clear that the judge is not ruling against the existence of some kind of notion of special usage rights that attach to concentric drop out pivots at the rear axle. So, for example, to build a bike with a split pivot that has a similar LR curve to DW's own bike designs would be infringing. A better result, in my view, would have been a restriction of the patent to very particular mechanical features of the dropouts. That would mean that design approaches could be freed up and people could stop losing sleep over who is going to sue them next.

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This news blog has 12 comments.

Added a comment about video Introducing the 2014 BMC Trailfox TF01 29 10/14/2013 12:45 AM
C138x104

There is a lot to like about this bike, but some bright types who have put it through a suspension physics simulator have concluded it is 140mm not 150mm as claimed. It doesn't bother me, except insofar as it is false advertising, because long travel 29ers are not an especially good idea.

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This video has 5 comments.