Aaron Gwin's winning
chainless run at Leogang in 2015 is firmly cemented in the history books, and it's often cited as an example of how much better a bike's suspension can work without a chain. Is that actually the case? And what about pedal kickback, another phenomenon that some riders say they can immediately notice, while it's not an issue at all for others?
Steve Mathews from Vorsprung Suspension dives deeper into these topics with several excellent examples that make it easy to visualize exactly what's happening out on the trail.
If you'd like to learn more about anti-squat, Pinkbike's Dan Roberts recently put together an in-depth primer on the subject - you
can read that here.
Me like ride mountain bike.
Me glad engineer man/woman design bike to make it ride good.
I still remember when I took a physics faculty and got a teacher who actually understood physics, as opposed to a "standard" teacher which could only draw formulas on a blackboard.
I have a box of worn out DA and XTR chains. I will sell for 100 bucks (will even throw in shipping - I am a nice guy) SO YOU TOO can be guaranteed that your chain will bust at the start of a run! Almost free speed. Also use the wrong chain tool to make a failure certain.
* even at higher speeds the hub will still get engaged as there is a lesser degree of engagement. And so hubs that have instant engagement will have the most kick back
The other factor, as Steve describes in his video, is chain bounce. This adds another variable, though the force of the tug at your feet and your suspension due to chain bounce is not large, compared to the forces moving your suspension and the force required to support your body during an impact.
Hardtailer private joke; sorry.
I agree that most tactile hand should ideally run front brake. Or is it that the tactile hand should run the brake thats easy to lock up? Hmm
Steve is a f*ckin wizard. Reminds me of Jesse from Fast and the Furious.
@optimumnotmaximum: Was I wrong? Here's what I wrote to you a minute ago in the other thread:
1. Somewhere in this thread - or maybe it was in the forums, or maybe both - I already mentioned the inertial effects of the chain. This isn't the first time someone has thought of it. Steve wasn't the first, I wasn't the first - I'm sure someone thought of it a hundred years ago. Most aspects of bicycle physics have been known for a long time.
2. While I don't disagree with Steve - he's both tremendously clever *and* has outstanding critical thinking, so I doubt I'll ever strongly disagree with him - I wish he had done more to address the magnitude of kickback due to the chain bounce effect. It's really not much. His point is that it's an often overlooked variable and it's non-zero, but it's not huge. The force you feel in your feet due to supporting your body weight during an impact is so much larger that it's unlikely the possible addition of the chain bounce effect will even be felt, let alone cause enough of a detrimental effect to be worth worrying about.
I also dont think you feel a big kickback, but i assume there is a negative effect on how freely your suspension is able to work.
1. You said I "was right and wrong at the same time". I wanted to address that remark by pointing out I *did* mention the inertial effects of the chain.
2. I'm not going to derive the equations, but you can do an experiment: Hold a chain in your hands. Fold up some of it in your hands and allow about as much distance of free chain between your hands as the free span of chain between your chainring and cassette. Pull it slightly tight between your hands - about the same tension as your derailluer creates on the chain when it's on your bike. Now bounce your hands up and down and feel how how much it pulls your hands together. The force you felt is more than twice the force that would've been created on your feet (because the chainring is not as large as the crank). This isn't the most accurate experiment, but it gives a rough idea of what could happen, *if* it even caused the hub to engage.
3. No, it does not make it impossible for the freehub to disengage. It simply adds another way in which the driver *could* engage, but engagement does not necessarily happen - and if it does, you just felt how little force is transmitted. Compare that to how much force your feet experience from smashing into things on the trail. The chain bounce effect is not large. As Steve mentioned, if the top run of chain slams into the chainstay or a STFU Chain device, the force is reduced further.
www.youtube.com/watch?v=9N2RvBO9HeY
Good discussion with Seb, as always. I see your point on the influence on suspension motion, but it seems like such a brief, transient effect that it could be lost in the noise, including during the period when the tires are loading up and compressing. The force acts over a pretty small distance and duration, especially if the chain motion is partially restricted by the upper run hitting the chainstay and the lower run being restricted by a clutch mechanism, and the total energy is small, relative to other inputs. Not saying I disagree, just that the mentioning of this effect has caused it to be over-represented in the mind of readers / viewers.
Thankfully, the effect is easily testable, albeit qualitatively, via the absence of a chain, turning the clutch on and off, supporting the lower run of chain, etc.
Any insights into how non-linear the "pain" response is, w.r.t. force or how to identify and optimize comfort from the data? I'm assuming it's primarily a function of maximum force. Understandable if any conclusions are proprietary information.
Found it.
Neutral gear.
This is why full trap chainguide with non clutch derraileur is besr
xkcd.com/793
Which, it's not.
However, the reverse is also true - if you're pumping through a depression where the ground level is fundamentally dropping away from the trajectory of the bike (a quarterpipe is a massive version of this), the more force generated, the faster you'll come out. Imagine even rolling off a kerb VERY slowly - as the wheel rolls over it, the force generated on the back side of each wheel will accelerate you forwards.
You can see the bike land and torque from chain takes a minute to pull the wheel, but it does. The trick being that the bike's got to be in a pretty small cog to amplify the force.
I have 1999 Cove G-Spot and i'm surprised more bikes don't use the design.
I guess its more complicated and requires more maintenance.
Thanks for the tech.
Put a single pivot in a place that balances the tractive force against the CG to accomplish 105% AS without taking chain tension into account.
Run a bottom bracket that acts as a jackshaft through the centerline of said pivot. A chainring on each side. One has a chain to the cassette, the other to the crankset.
Go one step further and put a geared hub on there, no tensioner needed as there will be zero chain growth.
If I read correctly, the starling DH bike would be a prime example if this. Right?
Also, a gearbox of the right design that has its output concentric to the main pivot could eliminate the need for the intermediate chain entirely, right?
Packaging would be an issue though, and the design of the gearbox would have to be done in conjunction with the bike design.
In any case, for a singlespeed I think the starling has the right idea. I’d like to see an enduro bike with the same concept
Now if only I knew what a jackshaft is...Regardless I'm positive that Dick Pound has one.