stillunimpressed

@Cord1: And then there is the Yeti E160 6 bar linkage, aka SIXFINITY, which came along more recently. The Yeti linkage, like the Atherton/Robot DW6, is actually a good linkage (and far and away superior to the Felt Equilink 6 bar - now defunct if I recall correctly - that shows some superficial resemblance to the Sixfinity).

I take the opposite view. With the chainstay growing 24mm during the course of travel bikes like this should have the shortest practicable chainstay. If you could somehow fit a really short 420mm chainstay in there (which would grow to 444mm at suspension bottom out) these two bikes would be close to perfect. Also, bicycle stability at high speed is conferred not only by chainstay length but also by wheelbase. Anyone deeply concerned about stability at high speed should probably look at the longer of the available bikes and see how closely the Effective Top Tube and Seat Tube lengths meet their needs. Nothing about the cockpit of the Large bike makes me think it would be unsuited to a Medium rider towards the taller end of the range.

I think Dan Roberts nails the topic of anti-squat and does so in terms that people without specialised training can understand. But I did find one dubious statement in the article. Speaking of a rider climbing a hill Dan said,"If in this situation your bike has a tendency to squat then it won't take much acceleration for the effects of the squat to remove all the load at the front contact patch and you're left with zero traction." I think that is somewhat misleading and I would like to try to explain why. Dan, it should be said, sets the scene very well. Of course there is danger of losing traction at the front wheel while climbing. And, at the moment of the acceleration pulses it is conceivable that the front tyre might lift. And, the experience of suspension bob while riding up hill is certainly disheartening. Just when you are hoping for a bit of acceleration the bike depresses under your pedal stokes and it moves lazily and in a wallowing way up the hill. Your energy is being lost into this bobbing mess with the cyclical compression of the suspension happening just when you put in your most vigorous exertions meant to make the bike pick up some pace. That is truly a terrible riding experience. Personally, I can't stand suspension bob. Now, despite correctly conveying the terrible riding experience that will be offered by a bike with a tendency to squat when riding up a hill it is misleading to imply that bikes with a tendency to squat are especially prone to traction problems. On the contrary bikes with a tendency to squat may offer better overall traction compared to bikes without that tendency. If we forget about the front wheel for the moment and only consider rear wheel traction it is not hard to see that squat to some extent (despite the poor riding experience it offers) is a useful modality to reduce traction robbing cyclical pressure (down force) variations at the rear contact patch. When climbing on loose or rough surfaces the greater amplitude of the pressure variation at the rear tyre contact patch of a bike with 100% AS or more makes such a bike more prone towards momentary losses of traction with the wheel spinning slightly and intermittently as the rider tries to propel the bike up the hill. Dan is well aware of the traction robbing nature of pressure variation at the rear contact patch but fails to weigh up the full significance of that insight for the climbing context. Additionally, when riding up a hill on a surface that offers good traction it is in fact the higher anti-squat bikes that will have a greater tendency to lift the front wheel. Why? Not losing any energy into squat the higher anti-squat bikes will offer greater acceleration potential and as acceleration is what lifts the front wheel of the bike that will be something that the high anti-squat bikes are more prone to. None of this means that 100% AS bikes will offer a poor climbing experience. There will be very little suspension bob and that is a big gain. Furthermore, human beings have limited strength so we do not only need bikes offering good climbing traction but also efficient climbing. A bike should get a rider up a hill without exhausting them due to energy being lost into squatting of the suspension. Riders want forward motion not squat. Additionally, most human being are unwilling to devote more time than is necessary to making their way up a hill. A bobbing mess that seems to want to prolong your climbing suffering is experienced as a undeserved punishment by many riders. And, as it happens, squat is only one way of improving traction and not a very good way. Traction is also improved by better tyre compounds and design. A good selection of gears to deal with different riding scenarios is also a great help to balance traction and efficiency.

That is exactly what happens with a bike that has less than 100% AS or isn't equipped with a shock capable of compensating for squat with copious amounts of low speed compression damping. When going up hill the bike necessarily slows in the lulls between the strongest acceleration pulses imparted by the riders pedal strokes. For a low anti-squat bike (without other shock tricks) the suspension squats during acceleration pulses (and squats to a greater degree while climbing hills) and returns to Sag between these pulses when acceleration forces (squat and anti-squat) die away. It is suspension bob that we experience as we are riding, not squat or anti-squat. The disequilibrating (suspension compressing and extending) acceleration forces that we call squat and anti-squat acting on the suspension are capable of producing mayhem but on a bike that mayhem is always expressed as suspension bob. Suspension bob is not something you experience riding a bike with a well designed suspension configuration. But achieving a bob free ride on a suspension bike requires either i) balancing squatting force with anti-squat or ii) the use of relatively advanced shock capabilities like dialing in additional low speed compression damping or using some form of inertial valving. Another option is iii) physically altering the drivetrain relationship to the suspension geometry during the course of travel - GT and Lapierre both offered takes on the floating bottom bracket idea - but these attempts to create a bob free suspension using a floating BB seemed to offer no advantages over the other already mentioned solutions which were, in any case simpler. Also, getting these drivetrain varying tricks to work still required carefully balancing compressive and extensive acceleration forces and/or use of a precisely tuned shock. If you are getting suspension compression only while climbing a hill (n.b. all suspensions compress to a point beyond Sag while climbing hills for the reason mentioned in the article - due to the changed body position of the rider relative to the bike more weight shifts onto the rear wheel) that is because your bike has a good balance between squat and anti-squat or because you have a very well tuned shock. But that doesn't mean the writers comments were incorrect. The writer was referring to bikes with an imbalance of squat and anti-squat. Those bike do bob (assuming no special shock controls) and they bob worse when climbing hills.

Something else relevant to your point is that the Yeti Switch linkage leaned on aspects of the Santa Cruz VPP suspension and the creator of the Yeti linkage worked with the Santa Cruz suspension engineering team for a while before 'inventing' the Yeti Switch linkage. Coming up with new linkages is a bit of a game. Anyone who has played with software that analyses linkage kinematics probably tried out something like the Yeti Switch or the Madsen linkage years before Earle or Madsen claimed them as their own inventions. There is something very dubious about patenting anti-squat or anti-rise curves. A direct copy of a given linkage ought to be patentable but we are not looking at that situation here. Arguably, the Madsen linkage isn't an optimal variant of linkage type that he is experimenting with. If the upper linkage was located in a more rearward position and the link was shorter (and therefore rotationally faster) the anti-squat curve when driving small cogs (the obvious weak point of this linkage configuration) would probably be improved a lot. Those high anti-squat numbers when driving small cogs (32 tooth chainring/10 tooth cassette cog) are too high. Also, a linkage similar to Madsen's but with a more rearward and shorter upper link (with the same horizontal(ish) orientation around Sag as the current link) would naturally lead to a switch/rotational reversal in the lower link at some point in suspension travel! It goes without saying having a switch in the suspension linkage action definitely would result in a patent violation lawsuit. That is the world we live in.

I think you are right. The design does work from the same playbook as the original Yeti Switch (which has found a new home at Alchemy Bicycles). I would point to four differences. You may or may not consider the differences significant. Unlike the Yeti/Alchemy linkage this linkage design i) does not use a 'switch' or an inflection point at which the direction of rotation of the lower link reverses and despite that manages to replicate the anti-squat curve of the Yeti quite well. Also, owing to ii) the path of migration of the IC achievable with Damon Madsen’s linkage design it would appear that a rising anti-rise curve characteristic of classic horst link/FSR and split pivot designs can be fashioned using dual short links. While there is no agreement on this point it has been argued (and I think the argument is correct) that a rising anti-rise curve makes for good traction while braking. Damon Madsen’s linkage design iii) locates the lower link is in a different physical space above and forward of the bottom bracket unlike the Yeti/Alchemy lower link which is above and slightly to the rear of the bottom bracket. Finally, Damon Madsen’s linkage design iv) uses a completely conventional short linkage bar for the lower link unlike the Yeti/Alchemy lower link which is implemented using special concentric hardware. Most of these points, not all of which have kinematic implications, if they were ever debated in court, would probably result in Damon Madsen’s linkage being considered original enough for any patents on the linkage to be reaffirmed and consequently Madsen's linkage design could probably withstand a patent challenge. That won't stop anyone from making that challenge, of course. It wouldn't shock me if David Earle (who was awarded the patent on the technology that the Yeti Switch bikes were based on and the Alchemy bikes are still based on) decides to go to war with any mountain bike brand that starts to sell bikes using Madsen’s linkage.

Just doing some visual checking of the path of migration of the IC this linkage does look very interesting. This linkage seems capable of reproducing an anti-squat curve similar to a Yeti Switch Infinity or Santa Cruz VPP suspension, which is definitely a good thing, while offering a rising anti-rise curve quite similar to the best horst link bikes. Dave Weagle seemed to have something similar in mind with his recent DW6 suspension but Damon Madsen seems to have got there in a less complicated way. This is a very good suspension design. I don't doubt that it will become sought after, if it goes into production.

@blinkpike: Not quite. There is no real pivot at the IC. The main consequence of raising the IC by reorienting the short links slightly would be to ruin the good kinematics of the bike while failing to produce a meaningfully rearward axle path.

@tcmtnbikr: You aren't missing anything. As you correctly said, "Whether the link is in compression or tension has no impact here in the forces analysis." People are talking in magical terms as if the motion of the rear wheel mounted to a floating link (rear triangle) can somehow be controlled by 'chain force' (in this case by tensioning the lower link rather than compressing it) when in fact the link is invariable in length, rotates on pivot axles and must act wholly in tandem with the four bar linkage according to the forces imparted into the suspension by rough terrain that activates the suspension or the cranks accelerating the bike and occasioning some weight transfer onto the rear tyre. Trivially, chain tension can influence the behaviour of the rear suspension, of course. Why? Because, he/she who pedals determines how rough the terrain to be traversed will be and how fast the ride will go! But this tells us nothing about how the suspension works. The way some commenters are talking here following Richard Cunningham's lead treats chain tension as something that actively governs suspension linkage behaviour directly and implies that chain tension can and should be used to achieve some sort of stability of particular links without considering the linkage assembly that the singular link is just a part of. But, no stability comes by that route. It comes from the kinematics of the bike. Adding talk about tension on links that has somehow made its way from the chain and into the links (instead of the chain and the spinning wheel) is meaningless.

The Druid looks to be a well designed bike - decent kinematics, low pedal kickback, a rearward axle path that should offer a a very controlled and compliant ride - and while the leverage ratio curve seems more progressive than is typical for an average 130mm suspension bike, on this one it seems fit for purpose.