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As for high pivot, a up and then rearward path would be very hard to achieve with all the pivots on the other side of the curvature...
As funny as the parking lot test and the reasoning seems daft, I believe it's a big influence. Just as weight has a huge influence, as all the people, when learning how much a bike costs, ask 'how much does it weigh'. And when someone buys something new, everybody lifts it up to see how heavy it is. And it has NO bearing on the performance of the bike, yet is something we all do.
As for sluggishness, I don't see why a high pivot would be sluggish in and of itself. Maybe it's byproduct of the idler, which I think is the real PITA with a high pivot bike, as most people say it's noisy. I can imagine why and I'm often pondering how to solve that.
To be completely honest, I've never ridden a high pivot bike, but would love to, as my prefered style of riding is going reasonably fast on reasonably chundery ('natural', not bermed out, smooth trails) and I can't jump for shit and I'm not a fan of going slow on technical stuff. Point and shoot straightline through rocks? Love it. A long 29er is magical in stuff like that and a high pivot would be even better.
But yeah, I can see how people could not like a high pivot bike as the front-rear weight distribution changes through the travel, the idler can be noisy and the parking lot test. The chain length 'issue' is not an issue as that is dealt by with the idler specifically. I actually think a high pivot design could be the solution to 29ers and the like as we have problems getting big wheels at longer travels under the seats plus the axle paths are getting more and more forward the bigger the wheel gets due to the requirements of antisquat and due to the BB height relative to the rear (or both) axle.
Imagine the rear axle rotating around the BB at a constant distance (giving you little to no chain stretch, so no pedal kickback), the higher the rear axle starts in the travel, the more forwards it will move through the travel. THe smaller the wheel (or the rear axle starting under the BB eight), the more rearward you can go in the beginning of the travel. With an idler you move the 'effective' BB (chainline wise) higher up to whatever height you want.
It's basically a single line that gives you X amount of antisquat in a given gear for a given rider and for a given sag value. For the given three variables, the line is the same for a multi-pivot bike, but you need to drop the IC on it, not the pivot itself, which means you can move the links around a bit more. Plus the antisquat characteristic through the gears and travel will then be different.
Anywho, the main limiting factor, besides the antisquat characteristics (maybe not as important on a DH bike though), for the height of the main pivot is the pedal kickback, caused by the chain stretch. That's why I said 'relatively high', as I'm suspecting the two bikes had a relatively high pedal kickback value due to the height of the pivot location and not running an idler. So yeah, 'relatively high for an idlerless setup', not 'completely reaward axle path high'.
With correct pivot placement, the pull on the chain resists this pedal squat. Have too much antisquat (as mentioned above) and the chain will pull the rear axle towards the BB (thus raising the bike).
The thing is that with chain driven vehicles you have two antisquat components, one comes from the geometry itself and the other from the chain pulling the rear axle forwards. With a normal layout the chain is the main antisquat component. With a high pivot the suspension geometry enables the rear wheel trying to 'fold itself under the rider' sort of thing. This gives a considerable antisquat component by itself and adding the chain in a normal orientation will give tons of antisquat. That's why you use an idler to lessen the effect of the chain on the antisquat levels to bring to a reasonable level.
That and to prevent insane amounts of pedal kickback.
Plus I don't see why that kind of axle path would work, the 'catch your wheel and try to buck you' hits are usually relatively small and come quickly one after another - they are short travel events that need to be dealt with quickly. The deep stroke events are usually more of a huck to flat kind of event. Therefore I think (could be wrong) that a rearward axle path is most useful at the beginning of the stroke and around sag and later in the travel it doesn't matter as much, if it's rearward or not.
A spare bike for telemetry as Specialized use to do usually doesn't have a custom worldchamp paintjob.
Or do you guys think that we will get three separate bikes? DH race, Parkbike and an Enduro?
See how long this gets taken down.
Fun fact... I got to meet Horst at the AMP shop in So Cal on my way to my first DH race in Laguna in the late nineties. Same trip that I was accused of burglarizing Marzocci.
The Druid (if it's being mentioned), the new Devinci (again, pedalling wise but not braking wise, since it's a bit murky due to it being a Split Pivot), the Supreme, both Deviate cycles models, the Actofive designs and the old Zerode DH bikes are all single pivot designs.
If physics is correct, a single pivot high pivot design should have a bit more braking induced squat since the brake link (when braking) wants to be rotated forwards (the link usually does rotate forward going through the travel) and the rear axle pulled back. A rearward axle path enables this second part of the brake induced squat, which is less present on more conventional designs with the more forward moving axle path (where during braking the rear axle is thus pulled back and out of the travel, but the link still wants to rotate into the travel).
For what it's worth, I think high pivots could bring quite a few benefits into mountain bike designs going into the future (more space for the linkages, tyre clearance, less seat tyre buzz, better kinematics, less pedal kickback but still good pedaling characteristics, etc.), but the idler is and will be a big problem. It's logical that it's noisy, it's less efficient than what we have and it makes the bike look a bit more complicated. If anything, gearboxes could be the answer with the output shaft not being concentric with the crankarm axle, thus making the output higher and facilitating a high pivot design without an idler.