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I would say there is also probably an argument against ignoring any windup on a URT bike but let's be honest pedal kickback is the least of this bikes issues.
FWIW those numbers come from a different linkage solving tool; there is some errors in Linkages pedal kickback algorithm (a term from the full equation is missing based on linkages own theory).
There are some slightly weird things happening when you have a concentric pivot point or an idler, where you still can get some kickback because of the chain wrapping and unwrapping if I'm not mistaken, but you don't have this effect with an URT. Therefore 'no kickback'. The issue is the whole triangle AND the BB itself are rotating. But the BB is rotating forwards.
Still, no chain growth, no kickback... Kinda like on a hardtail.
"pedal kickback is directly proportional to chainstay (chain length) growth"
It's not the chainstay growth but the chain growth which is compose of a few terms. The wheel wind can be ignored if you treat the wheel as locked.
Pedal kickback should not be treated as an absolute perfect number. It's really just an approximation to compare between bicycles to get an idea of how much of the phenomenon you will get in relative terms. There is too many dynamic properties such as impact velocity, wheel speed, and hub engagement involved to rely on a static number completely. It's also a metric created by a single persons research that was eventually rolled into linkage. Pole has a link to some of the original figures:
https://polebicycles.com/wp-content/uploads/2015/06/PedalKickbackCalculation.pdf (Original credit to Gergely Kovacs who behind LinkageX3)
And this is a recap of the different terms and variable in calculating the chain length change:
https://docs.syn.bike/definitions#def-chain
Cheers.
As for front triangle fixed, the cranks are fixed to the swingarm then. In that case, with the drivetrain locked, the cranks rotate in the opposite direction of pedal kickback, i.e. it's negative.
I know it's chain growth, but chainstay growth is the usual factor behind it. And I know it depends on the chainwrap angles and sizes as well. No worries.
Here's a hint to this person : learn to weld and machine yourself, and Make the bloody thing, Yourself.
I did that in the early 70s, first as a 12 year old. It's had me earning money, and making my Own frames, and Designing / Prototyping for manufacturers, for now over 5 decades.
It's a URT, no matter what 'scissor linkage' he's designed. So, having the riders mass going into the un-sprung mass total, the millisecond that they get off the seat. It's just dreadful engineering, if you can call it engineering.
A big factor in all of this is also the fact it's a ground up design from someone who hasn't done anything like this before. If you're a company offering these kinds of services to multiple customers, all of that expenditure gets shared between the customers and the final cost for one specific customer is lower.
It's known that Bruni is racing on blacked out Minions or shortys depends on the terrain.
Spech tyres are awesome and got great reviews from vital and other sites, but have a noticable difference in total volume compared the maxxis's 2.5/2.4 WT tyres.
We might see this new tyre come in an only 2.5 width and smaller total volume.
Bruni is known for his preference of narrower wheels - using 25 inner width rims.
This might be a killer option from specialized.
I haven’t tried the Grid Gravity, so perhaps it’s not up to the rigors of WCDH, but Specialized is taking their tire game seriously.
https://www.pinkbike.com/news/spotted-another-prototype-high-pivot-bike…
Side note: For once something was on PB first
Source, my eyes
Also they already made a higher pivot wilson with an idler, and shortly after axed their factory WC team. In hindsight it seams like they probably were just testing the idea before slapping it on a more consumer friendly trail bike.