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This is just a guy who has got entirely lost in the weeds. There is no "antisquat theory" that some cabal of bike engineers is pushing. Antisquat can be calculated several ways but the results are always exactly the same. It's a proportion of drive force acting on the shock to weight transfer on the shock. Moving your pivots anywhere on the bike doesn't change this.
Pedal-kickback is a much less well defined metric (especially when considering some of the dynamic effects) but the metric is still fundamentally tied to the geometry of a chain-cog system.
There is literally nothing special about this particular layout other than the 2-bar follower link. As an aside this is kind of cool; it acts like a movable seatstay bridge. To emphasize how un-exceptional this bike is here is a comparison to a 2020 Norco Sight which kinematically might be the most boring bicycle on the planet.
Two things to highlight:
- Antisquat is shown in both "static" and standard mode. Linkage used to offer both but moved to only showing the "static" figure. Functionally the difference is just if you consider the front triage fixed with respect to the ground or sagging into itself. While the numbers differ a little bit they are just benchmark measurements for comparison between bikes anyways so the absolute values don't matter much. I prefer the non-static measurement; it angles the vertical tire force with respect to the ground as the bike sags.
- You will notice that pedal kickback did not just vanish because of some miracle of geometry that Chris from Nanaimo has figured out like some dude from the DaVinci Code. In the squish videos you see minimal crank movement but it's also not in a large cog which dramatically drops the kickback levels (<12deg in a 32/20 config).
No, Matt said the Horst link one was better and quieter with the eerie feeling.
Chris did in fact say that you could propel the bike by bouncing.
“If you stand on the bike and bounce, you will be propelled forward. Pedal bob propels you forward.”
I suspect if you dug into the logic behind the "statics regime" you'd find a fundamental flaw or two. I suspect the logic is that if the IC is on the chain line then chain tension would have no net impact on suspension movement. While this might sound plausible, it has one major flaw... it fails to take into account the reaction force at the tire/ground interface.
You can propel any bike with chain growth forwards by bouncing on the pedals. If there's no force on your feet from the chain tension then you should be able to remove your feet from the pedals and bounce and get propelled forwards. That's not happening.
Yeah maybe I shouldn't be surprised that people haven't figured out riding ability has no relation to technical knowledge....being good at something doesn't automatically make you an expert on how that thing works
Now I want to solve bike design as much as the next guy but after that description of pedal kickback and finally watching the video, I gotta ask..
If it sounds like a cult leader, operates like a cult leader and looks like a cult leader. Is it a cult leader? Old mate is addicted to his one truth.
I think the article and related comments are gonna age like milk.
Can someone just plug it into linkage and put an end to this. You can't just keep adding more links and expect the fundamental concepts of linkage suspension to change.
My theory is he's an owner of a bearing company and looking to increase sales via delicate subterfuge.
I’ve looked at linkage and it doesn’t give me any more information, I can’t see visually how it’s different or why it behaves differently. The guy has passion, Matt says it feels different. Everyone else says it’s not possible. Hahaha I’m still lost.
There's nothing to get lost about. He's made a fairly conventional linkage system that has high overall anti-squat and antirise. It just looks whack and he's talking buffoonery. It doesn't go any deeper.
I think the only thing I can add to the discussion of the design itself (as opposed to the confused and confusing messaging) is an opinion that the "knuckle" (his words for the linkage bits bolted to the seat tube) that is apparently necessary to prevent the rear end from flopping about should have indicated that it's a fundamentally compromised design from the start. The "knuckle" assembly adds unnecessary weight and the extra strengthening required in any final product to eliminate it will also add unnecessary weight.
He claims that his selection of pivot locations somehow gives it special powers so a question for the experts: other than what we already understand about LR, AR, AS chain growth etc., is there anything else meaningful that moving those pivots around on a four bar linkage can do that isn't as well understood?
People will feel a lot of things if you prime them before they try them.
EDIT: I have a friend who, whenever we're testing something new and he is the first to test, always says "you'll try it out yourself" when I ask him what it's like and when you get your turn, he asks what did you feel or think, not "did you feel x". Because he wants an unbiased feedback.
Anywho, all this talk about kinematics is all well and good, but the first thing I though when I saw the bikes was "even if it works, who the hell is going to make a frame like that??"
Complicated layouts make for complicated design, manufacturing and maintenance. And most simple bikes these days work plenty fine.
The knuckle design has been used before on the GT Fury that the Atherton's won many WCs on. I don't think there's anything wrong with it provided the rest of the suspension makes it worthwhile.
The level of AS really only gives information about how well the drive forces balance the inertial forces on the suspension, normally asuming the COG of the rider is fixed relative to the front triangle. It doesn't take into acount the rider moving and reacting to the bike moving nor does it give information about sensitivity or stability when there is a perturbation. The variation of the AS level with travel combined with the leverage ratio and shock characteristics do give some information but there isn't a widely used approach to interpret that. So, I think there is room for improvement but I don't think AS will be replaced as it works very well, especially for smooth seated pedalling. Instead I think some additional criteria will be developed to explain why some bikes with similar AS levels still behave differently.
AR is more difficult because it is so strongly depends on how the rider brakes and their preferences, as discussed in one of the Frameworks videos where the riders wanted a significantly higher level than Neko found best.
If you look at how much of the anti-squat is due to chain tension as opposed to axle path, you can get a fair bit more information. The same anti-squat numbers may get you identical seated pedaling, but if the component that’s due to chain tension is different you’ll get different behavior on larger scale compressions.
I started a pot on main forum and was told to check in on this thread.
https://www.vitalmtb.com/forums/hub/feedbackchain-growth-relation-chainringmain-pivot-distance-single-pivots#comment-665481
Lot of good info here but maybe a bit more then I need right now for what I am trying to do.
Maybe a short version of my question is:
If I bring the top of chainline in line with the main pivot on my V2 Meta TR; it currently sits below it with a 32t ring, will this result in a lower amount of chain growth in relation to where it currently sits?
I am hoping for less crank rotation as the suspension compresses.
I will be (hopefully) accomplishing this by putting together a HIGHLY sophisticated idler pulley consisting of an old MRP roller and random hardware from Mcmaster-Carr.
Thanks for any insight to this question.
Is there a good resource I can refer to that details the separation of the components of anti-squat (even if only qualitatively)?
Have you looking into using an Ochain? I don’t know the answer to your question.
The reason I told you to check out this thread is mainly because you used the word "fabricating". Haha. I thought that sounded like you were going to spend a bit of time and effort making it, and thought it was worth putting a bit of proper design work into it before making something that might not do what you wanted. Or does what you want but with terrible side effects.
The answer though is is yes. (edit - actually no, see below)
four things to consider:
If you're going to pedal it, you do want some pedalling support supplied by chain tension. A neutral setup with zero kickback won't pedal neutrally. It will bob like hell.
The main pivot is usually roughly vertically in line with the chainring for a reason, not forward or behind it too much. too far either way will give you really inconsistent results as you move through the travel.
Your chain is still going to bounce around and you're still going to feel it. kickback is one aspect of pedal feedback. Ochain helps with both aspects.
There's a lot of force on the idler. If you're expecting to get away with anything other than a metal sprocket, it's going to be extremely rough/loud/draggy/short lived.
Back on the second page of this thread I posted a diagram depicting the basic forces at play here. In the description of the calculation, the acceleration and chain tension forces are combined into one resultant force. Instead of doing that, both can be analyzed independently. If you say that the sum of the moments created by those two forces has to be a certain value, if the moment from the acceleration force increases then you can decrease the moment due to chain tension. Without an idler, generally speaking both will increase together as pivot height increases (there are ways to increase one and not the other with some bizarre IC placement). With an idler you can choose how much you want chain tension to play a roll.
The IC can be under the chain line and chain tension can still pull the suspension up in its travel. The point at which chain tension is neutralized is when the IC is located on a line that intersects the hub and the cranks (idler in the case of an idler bike).
Do you mean the center point of the hub and cranks (rear axle and center of the bottom bracket), or do you mean the top of the rear cog that the chain is wrapped around and the top of the chainring?
Center of the BB
Yeah duh, sorry. It's been too long since I've pissed around with this stuff.
Very familiar with the O-chain, I am all about that product.
I actually presented a similar concept to a local bicycle manufacturer a number of years back. Owner seemed interested but nothing came of it. A few years later I brought it up with some of the engineers and they said they had looked into and the data did not show a benefit with regards to feedback/suspension performance.
After Gwin's chainless win (I imagine I was not the only person to do so) and his comments at the end of his run (Which I recall was edited out in the replays) I started thinking about how free movement at the chainring could mimic the chainless feel; I have ridden after a broken chain a number times and the difference in suspension performance was always obvious to me.
A few months after I spoke to the engineers the Ochain was released...Apparently some benefit after all!
Basically, I would get an Ochain but it just hurts too much. I am kidding, of course.
The idler is just an intellectual/mechanical project for me to play around. It should help keep me distracted from constantly messing around with +/- 5-10mm changes in reach/stem/offset in order to find the PERFECT balance of my body mass between front and rear axles. I could also just go for a bigger chainring but that would not be nearly as fun.
Thanks for the reply and info.
Haha, yes in an ideal world I would actually creating an actual bike part. I have some experience machining. If I had access to a lathe, some aluminum and a tough-loving, chain-smoking journeyman machinist yelling at me from the next machine over, I might be able to pull something off; although not to tolerance and most likely after scraping numerous parts.
My ideal version of what I am cobbling together (That word is a more appropriate description of what I would be doing.) would be to machine a replacement axle for the main pivot that would have the idler mounted to it.
Thanks again for the info , it helps alot.
Awesome, thank you.
I know starting leverage ratio has been touched on a bit here. I find it interesting companies like Raaw and Kavenz are marketing different rocker links and catering higher leverage links for lighter riders. I'm on a Kavenz and I feel like I'm on the cusp (73kgs) between their linkage options and am wondering if I'll find any benefit going to a higher leverage/more progressive set-up (30% progression vs. ~24% progression). For a high pivot bike, at times I was expecting it to be more plush/magic carpety, but instead, I find it quite supportive even if its at the cost of some feedback through my feet, and I am wondering if it's due to that lower starting leverage curve, etc. It is very consistent however throughout its travel, which I appreciate.
Going to the more progressive linkage will get you a softer off the top feel. You'll likely want to go up in spring rate to keep sag similar. In my mind, the whole starting ratio thing is more of a question of whether or not spring rates will work out for people or not. If you say that you want a heavy rider to be on a 650, then you have to limit starting leverage ratio. Personally I feel bigger riders get the most benefit out of a longer shock stroke as opposed to a more linear bike. For example, we did a 180 mm linkage for the Crestline DH bike that still used the 250x75 shock size. I'm just a tiny bit lighter than you and for me it wasn't great. This was mostly because without doing a bunch of custom tuning, the damping tune was just too stiff. For heavier people that was a non-issue though. In fact it let them be more in the middle of the adjustment range. Provided you can retune a shock and get a similar thing, but I think there's value in an off the shelf tune just working right.
I wonder if you have correct spring rate and clicker settings. Those 2 options can dramatically change the feel of the bike. Not saying that all high pivot have a magic carpet feel, but maybe there is a set up issue that is off. Everything plays together, leverage spring and damping setting.
I've tried running compression wide open and it definitely helps with the bike feel much more plush, but I lose out on quite a bit of support as well as control as the rear gets a bit busy. I usually don't mind running in a bit more compression at the expense of comfort for more support and consistency throughout the travel.
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