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TrueScotsman

Monkey
Mar 20, 2002
270
2
Scotland
OK, time for another technical, in-depth discussion- this time;
Pedal feedback
How noticable is it? What bikes are worst for it? Are most bikes faster chainless? Is it the other side of the "high anti-squat" coin?

C'mon people, let's get tech.
 

Sandwich

Pig my fish!
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May 23, 2002
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I've often wondered if you could get some acceleration by having high "pedal feedback" and keeping the pedals steady. I would imagine a rider's weight could keep the pedals still over most bumps. In theory, the rear wheel would pull itself forward as shock force is absorbed.

I've posted that before, and most people discounted it since at most speeds the cassette wouldn't be able to catch up and actually turn the tire. So, does pedal feedback really matter in any instance besides actively pedaling the bike?

I'd say more than 100% anti-squat would be beneficial in some cases, as it would cause the tire to dig in to propel the bike forward. I actually like the pivot location on my Trek Fuel as it allows me to be right about even in the middle ring, and in the smaller ring there is some noticeable feedback. It's a neat manipulation that allows some extra bite on super steep climbs. I've noticed my ability to get up steep hills lowers when I test rode an FSR bike and a few others.
 

TrueScotsman

Monkey
Mar 20, 2002
270
2
Scotland
I'm not sure that MORE than 100% Anti-Squat would help dig in the rear tyre, but I would agree that less than 100% would tend to squat (like some FSR designs?) leading to a slight loss of power to the rear tyre. 100% A-S should be the ideal as regards the trade-off between traction and loss of power. To try and get the tyre to "dig-in" more is kinda like pulling yourself up by your shoelaces, no?- It can't be done (baring initial transient reactions)???

As for acceleration from pedal feedback- hmmm, i don't know? I'm sure I remember DW or Socket talking about freewheel speeds not being high enough to engage this in real life.
 

Sandwich

Pig my fish!
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May 23, 2002
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Well let me see if I understand my terms right. I am under the impression that 100% anti-squat is a chain reactive force that counters all the weight/mass transfer the suspension sees under pedaling. So 0% would be no chain force/feedback, 150% would be an extensive force beyond the weight of the rider (what I'm talking about) and -50% would actually be the "bucking" or pulling up by the rear wheel (pro-squat).

If I'm wrong, please correct!
 

TrueScotsman

Monkey
Mar 20, 2002
270
2
Scotland
Yes, you're right, but 150% "extensive" force doesn't add any more traction. It just compromises the suspension action that you need to track the ground. It makes it more like a hardtail. FS should trump HT on steep bumpy climbs.
 

Sandwich

Pig my fish!
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May 23, 2002
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I would think extensive force would help, to a degree. Certainly the monkey motion "pogo" bikes of the old days aren't ideal, but some level of "bonus" traction could be gained by going beyond 100% antisquat. I guess I like to think of it practically rather than theoretically- 100% antisquat on flat ground is not 100% on a steep climb. Weights are different and so is position. Add to that rider compensation (leaning forward, the "magic spot" or whatever MBA calls it) and extensive force is pretty welcome, where it wouldn't be on flat ground.

It would be interesting to have a bike design that allowed you to adjust pivot location and play with values in a variety of scenarios with data acquisition. Make the pivot even, ride up something steep. Put the pivot up high, ride flat...and so on.

I think on a DH bike at DH speeds, pedal feedback is super minor. My buddy just rode a Lapierre in whistler, which he loved. That's a bike that has a high degree of "pedal feedback" or extensive force or whatever on paper....in the real world, it works very well.
 

TrueScotsman

Monkey
Mar 20, 2002
270
2
Scotland
100% Anti-Squat- chain reactive force = weight/mass transfer due to acceleration (net effect=0)

0% Anti-Squat- chain reactive force has no effect on weight/mass transfer due to acceleration. (net effect=squat)

50% Anti-Squat- chain reactive force helps reduce the weight/mass transfer due to acceleration (net effect=1/2 squat)

-50% Anti-Squat- chain reactive force helps increase the weight/mass transfer due to acceleration (net effect= 1 1/2 squat)

150% Anti-Squat- chain reactive force exceeds the weight/mass transfer due to accleration. (net effect= -1/2 squat / 1/2 rise)

Things to remember- pedalling is a series of acelerations (hence why low/too high AS bikes bob) and that we are talking about weight/mass TRANSFER here- you cannot increase the weight on your rear wheel more that your total weight.

Also, as you say, it is all dependant on body position.
 

- seb

Turbo Monkey
Apr 10, 2002
2,924
0
UK
I remember accidentally loosing the chain on my Orange Alpine (on a descent) and immediately noticed how much better the suspension worked without a chain.
Certainly I enjoy riding my bike chainless, maybe this is part of why :)
 

TrueScotsman

Monkey
Mar 20, 2002
270
2
Scotland
Interesting concept, never thought about that.
Yes, i've often wondered about this. Some mates swear it's true, but is this just them compensating for a lack of chain by being smoother?

Also, Mojo did some tests down Fort Bill with and without chains and came up with a modified pulley/idler on the pivot that reduced the pedal feedback. I'll see if I can dig up a picture.

Also, friends that race the new Orange 322 prototype say it IS noticable since the pivot has been moved back and down (reducing the pedal feedback). Especially through rock gardens.
 

Acadian

Born Again Newbie
Sep 5, 2001
716
2
Blah Blah and Blah
here we go;

I've considered doing this to my own 224, but the question is....how noticable is it?
I think Cathro was running that setup for a while.

I did chat with Orange about that idler setup. Apparently they ran an idler on some of their 224's, but they couldn't prove it worked or didn't - they even did chainless runs and got some fast times doing that as well.

They also tried forward pivot, low pivot, high pivot etc etc and best DH frame they made was the 224 evo, only downside is they couldn't get the shock progression they needed - that's when the link bike was born and as we know, that bike also didn't make the cut. That's why they decided to make the new 322.

This is what Michael Bonney or Orange shared with me on the subject of pivot placement and the effect of the chain on the suspension:

"If you look at any HPV data the efficiency drops as you go to small cogs, an
11 tooth used as an idler is very small and chain will start to notch its
way (polygon) around rather than roll, chains actually work by passing power
from link to link so power gets used to pull the lifted roller onto cog when
its doing, chains are actually more efficient under tension, difference
can be quite big a 52/21 under tension can run as much as 5% more
efficiently than a 52/11 running no so tensioned which in a Dh race could be
seconds on a course with big pedaling sections.

There's way more to think about than just having a neutral pivot position"
 

fluider

Monkey
Jun 25, 2008
440
9
Bratislava, Slovakia
Suppa duppa LP Pendbox has been a miss-step, imo. I'm curious what else they'll come up with to replace defficient Pendbox. They even implemented it in their XC line.
 

TrueScotsman

Monkey
Mar 20, 2002
270
2
Scotland
Yup, fluider, I reckon the Pendbox is not ideal also.
Massive amounts of pedal feeback!- yes it will help it pedal like a hardtail, but it will also act like a hardtail through the rocks! Or bounce you off!

EDIT- here's a useful video of the pendbox system complete with added arrows!http://youtu.be/Vc_n9HWUFfM
 
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davec113

Monkey
May 24, 2009
419
0
I've often wondered if you could get some acceleration by having high "pedal feedback" and keeping the pedals steady. I would imagine a rider's weight could keep the pedals still over most bumps. In theory, the rear wheel would pull itself forward as shock force is absorbed.
It just bounces your feet off the pedals, so I don't think it's possible for the rider to keep the pedals steady.

The same force does help with climbing with the pedal force extending the tire into the ground. My old Uzzi VPX was a total pig but had more climbing traction than any other bike I've owned and I still can't clean a couple sections on my new bike that is almost 10 lbs lighter. The high bb on the Uzzi helped too...

It seems like bikes where pedal feedback is an issue are becoming increasingly uncommon as high single pivots aren't popular anymore. Newer designs have some PF in the 1st part of travel, but it's usually not noticeable unless you're running a granny gear... dh bikes are usually designed around a 38-42t front chainring, and of course have no granny to worry about.

I also agree a high pivot will work better w/o a chain (or a rear brake), but I don't think there will be much difference with today's lower pivots like the Session 88.
 

TrueScotsman

Monkey
Mar 20, 2002
270
2
Scotland
Okay, not convinced about the Lapierre PendBox idea and fuelled by insomnia (it's not even 5.00am here!) I set about redesigning the system so it's better regarding pedal feedback and I came up with.......UPendBox! (Up-end, geddit?- damn i need sleep!)

I used all the modern 3d CAD packages (erm.......Paint!);



As you can see the design/sketch/scribble acts like a high pivot up to 2/3 travel and then the BB moves back to counter high amounts of pedal feedback. And no, its not the same as an I-drive!

Anyway to get back to the original topic, how big a problem do you reckon pedal feedback is?
 

descente

Monkey
Jul 30, 2010
430
0
Sandy Eggo
what i would really like to know is the ratio of rider who use flats on bikes with high PF to riders who ride clipped in on the same bikes, and vice versa. seems like if you are clipped in, then it will negate the feedback bouncing your feet of the pedals, and flats would work very well on bikes that have low pedal feedback forces.
 

fluider

Monkey
Jun 25, 2008
440
9
Bratislava, Slovakia
I've been intensively riding only Banshee Rune that is by far a pedaller from different league compared to any HT I had ridden before it. I just have to stay sitting, or the noticable chainpull (pedalkickback) at granny ring will draw half of my energy out. In regards with pedalling, I call it chainpull rather than pedalkickback because it's not sort of kick you feel but something that is strongly and smoothly working against your feet. However in DH sections the same effect would behaved as short intensive kicks. But once on 36T ring and proper rear sprocket I can't feel significant pedalkickback even on full bottom out.

A high pedalkickback value in last third of travel must be pretty unconfortable because you're not pedalling, and when a major hit comes your rear leg that carries most of your body weight loses pedal from beneath the leg, and your front foot used for balance gets kicked.
 

davec113

Monkey
May 24, 2009
419
0
what i would really like to know is the ratio of rider who use flats on bikes with high PF to riders who ride clipped in on the same bikes, and vice versa. seems like if you are clipped in, then it will negate the feedback bouncing your feet of the pedals, and flats would work very well on bikes that have low pedal feedback forces.
I agree, pedal fb is much more noticeable on flats but clips don't fully negate the issue, just make it less of a problem.
 

Steve M

Turbo Monkey
Mar 3, 2007
1,995
23
Whistler
Yes, you're right, but 150% "extensive" force doesn't add any more traction. It just compromises the suspension action that you need to track the ground. It makes it more like a hardtail. FS should trump HT on steep bumpy climbs.
Well it sort of does actually, because it increases the transient load by accelerating your body mass upwards. The effect isn't that significant compared to what you lose by unnecessarily moving your mass around instead of having that energy propelling you forwards though IMO.

I remember accidentally loosing the chain on my Orange Alpine (on a descent) and immediately noticed how much better the suspension worked without a chain.
I reckon that's probably to do with the weight difference rather than pedal kickback - chains are heavy!


I've often wondered if you could get some acceleration by having high "pedal feedback" and keeping the pedals steady. I would imagine a rider's weight could keep the pedals still over most bumps. In theory, the rear wheel would pull itself forward as shock force is absorbed.

I've posted that before, and most people discounted it since at most speeds the cassette wouldn't be able to catch up and actually turn the tire. So, does pedal feedback really matter in any instance besides actively pedaling the bike?
Nah, I have run calcs years ago (they're on the monkey somewhere) that show it'd be pretty well impossible to actually "catch up" with the freehub in any reasonable gear combination with any realistic amount of chain pull. Besides that, there is no way you can introduce an acceleration of any mass by applying an unbalanced external force in the opposite direction! The only time you could actually legitimately gain acceleration from that kind of thing IMO would be a slow speed drop, where freehub rotation speed is extremely slow, and you're transferring kinetic energy in the vertical direction to kinetic energy in the horizontal direction.

So IMO no, pedal feedback is irrelevant for 99.9% of coasting situations.
 
Aug 4, 2008
330
4
Personally I hate pedal kickback. My poor chronically injured ankles hate the pain it induces when handling the bike wrong (some scenarios of braking through the rough stuff, etc.).

Ironically I haven't liked a single bike I have ridden without pedal kickback, except Intense! I lubed Intense! Dunno if it kicks back or not - but I didn't feel it. I guess that Santa Cruz has to have similar feeling.

So I hate pedal kickback in some scenarios. But I also hate bikes that don't have it, of all suspension designs I massively prefer single pivots of various flavours, FSR leaves me cold and VPP seems awesome. Thus the solution for me is to try to brake properly, unless I use the rear brake in Gnar - everything seems fine.
 

Steve M

Turbo Monkey
Mar 3, 2007
1,995
23
Whistler
So, are you saying that pedal feedback is not noticable/problematic?:confused:
Only in coasting situations. You notice it a LOT when climbing a trailbike, and you even notice it under hard braking on some bikes (rear wheel locked = no freehub releasing chain) like the 303.
 

TrueScotsman

Monkey
Mar 20, 2002
270
2
Scotland
Hmmm... okay, is this because when climbing the rear sprocket size is larger- meaning that the angle of pedal feeback at the cranks is larger? i.e. suspension hits "pull" more chain back?
 

iRider

Turbo Monkey
Apr 5, 2008
1,878
236
The same force does help with climbing with the pedal force extending the tire into the ground. My old Uzzi VPX was a total pig but had more climbing traction than any other bike I've owned and I still can't clean a couple sections on my new bike that is almost 10 lbs lighter. The high bb on the Uzzi helped too...
While I agree to a lot what you said I found that VPP and its pedal feedback has a downside. On slow grinder climbs with wet/muddy or loose sandy soil I have the problem that when you climb over a rock or root or a small step you feel the suspension working against your pedaling. To compensate you put more force in to not get hang up on the step and as soon as you clear it you get too much torque on the rear wheel and spin the rear tire out. Never happens when you above a certain speed but often in slow and steep climbs. What is frustrating is that you actually made the obstacle but spin out afterwards.
 

I.van

Monkey
Apr 15, 2007
188
0
Australia
I've been intensively riding only Banshee Rune that is by far a pedaller from different league compared to any HT I had ridden before it. I just have to stay sitting, or the noticable chainpull (pedalkickback) at granny ring will draw half of my energy out.
I have a Rune and this is the biggest negative of the frame. There is way too much anti-squat in a 22t chainring. When trying to stand up and pedal up a steep climb, I top-out the shock with every pedal stroke.:mad: sitting and spinning is ok though until it gets super steep.

I have tried a 26t and it is a bit better. I just have to convince my legs to man-up to grinding up the climb.
 

Sandwich

Pig my fish!
Staff member
May 23, 2002
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Nah, I have run calcs years ago (they're on the monkey somewhere) that show it'd be pretty well impossible to actually "catch up" with the freehub in any reasonable gear combination with any realistic amount of chain pull. Besides that, there is no way you can introduce an acceleration of any mass by applying an unbalanced external force in the opposite direction! The only time you could actually legitimately gain acceleration from that kind of thing IMO would be a slow speed drop, where freehub rotation speed is extremely slow, and you're transferring kinetic energy in the vertical direction to kinetic energy in the horizontal direction.

So IMO no, pedal feedback is irrelevant for 99.9% of coasting situations.
that's what I thought...but I'm thinking if you were to compress the suspension with firm pressure on the pedals (but no actual rotation) on a bike with lots of chain pull, at zero speed, you would effectively get some rotation of the wheel. Again, if the pedals are locked and no speed.
 

Pslide

Turbo Monkey
Yes, you're right, but 150% "extensive" force doesn't add any more traction. It just compromises the suspension action that you need to track the ground. It makes it more like a hardtail. FS should trump HT on steep bumpy climbs.
Hmm.

Friction force (traction) is increased as the vertical load is increased (Ft = mu*Fn). Isn't that what the "extensive force" is doing? It's converting a part of the power applied to the pedals into a downward vertical force at the rear wheel, thus increasing traction.

You can counter this vertical force with body language to minimize bob and maximize traction.
 

Pslide

Turbo Monkey
that's what I thought...but I'm thinking if you were to compress the suspension with firm pressure on the pedals (but no actual rotation) on a bike with lots of chain pull, at zero speed, you would effectively get some rotation of the wheel. Again, if the pedals are locked and no speed.
You'd feel this. And even with an I9 hub, I have never felt it.

There was a few times I thought I felt it on my Legend, turned out being the chain getting momentarily caught in the chainguide... :rolleyes:

Theoretically, if you were at a standstill, you could pump the bike up and down and propel yourself forward. Try it!
 

Sandwich

Pig my fish!
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May 23, 2002
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Yeah, all I'm talking is theory, in reality a small amount of speed would eat up that advantage very quickly, as Socket suggested, but for the sake of argument...
 

TrueScotsman

Monkey
Mar 20, 2002
270
2
Scotland
Hmm.

Friction force (traction) is increased as the vertical load is increased (Ft = mu*Fn). Isn't that what the "extensive force" is doing? It's converting a part of the power applied to the pedals into a downward vertical force at the rear wheel, thus increasing traction.
I stand corrected- but surely, as Socket said, this is just transient? Like the analogy of pulling yourself up by your shoelaces.

Or have I got the wrong end of the stick?
 

rbx

Monkey
I still think that by having an internal geared hub with a cc pivot at just the right height you could have 100% anti-squat(thru the entire travel) and have zero pedal feedback on top of that.
(same size sprocket)
 

TrueScotsman

Monkey
Mar 20, 2002
270
2
Scotland
I still think that by having an internal geared hub with a cc pivot at just the right height you could have 100% anti-squat(thru the entire travel) and have zero pedal feedback on top of that.
(same size sprocket)
I have thought this before, but I worked it out and the swingarm pivot/internal hub would have to be around 600mm (IIRC) above the BB!
 

rbx

Monkey
I have thought this before, but I worked it out and the swingarm pivot/internal hub would have to be around 600mm (IIRC) above the BB!
If you look at the Zerode bike on the linkage program and place the COM of the rider at (450,850)
I estimated the height of rider after drawing up a 2d CAD stick figure(real human proportions) figure standing up while accelerating.

Then the mid height would be at about 575 as you said so we are both using the same calculating method(i think)

So at 600mm is not far fetched because the zerode bike pivot is at 580mm form the ground!

P.S Also Zerode must use the same calculating method

Also theres a way of putting the main pivot cc to the hub and gaining zero brake squat...pm me if you talk any further:)
 

Pslide

Turbo Monkey
I stand corrected- but surely, as Socket said, this is just transient? Like the analogy of pulling yourself up by your shoelaces.

Or have I got the wrong end of the stick?
I personally don't think it's just a "transient" benefit. I think over 100% anti-squat has very real benefits in terms of steep, technical climbing (as a previous poster said), where traction is the limiting factor and not power.

I also think there's a benefit during a standing sprint, where you are mashing on the pedals and your pedaling motion is causing excess suspension movement (not from the chain, but from body movement), so you need additional anti-squat to counter it.

I haven't done the math, but if you are sprinting and your suspension is compressing not from chain force but from up/down pedaling forces, then energy is being wasted. Extra anti-squat will cancel some of the up/down movement, allowing you to apply more power with your legs.
 
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Sandwich

Pig my fish!
Staff member
May 23, 2002
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Is 100% antisquat really quantifiable, or is it more of a "qualitative" theoretical value? I mean, 100% is a great term to throw around, but the amount of chain torque required to achieve equal and not more or less mass-reactive force is going to change with rider positioning, bike positioning, suspension setup (soft or firm, if it's a position sensitive design it'll be at different positions of sag) as well as trail conditions and pedaling characteristics. Certainly "100%" can't be 100% of the time.

To Pslide's point- if you're using chain torque to counteract pedaling forces, you're also counteracting suspension forces. So, wouldn't you lose some "suppleness" in the suspension when you're pedaling and therefore using chain force to firm up the rear end? So yes, you won't be wasting energy against "bob", but you'll be wasting suspension capabilities. I think that's why, in theory, I think a bike with little or no anti-squat under non-climbing applications works well. That way the suspension is always working. It's then up to the rider to not mash pedals and activate the suspension.
 

TrueScotsman

Monkey
Mar 20, 2002
270
2
Scotland
If you look at the Zerode bike on the linkage program and place the COM of the rider at (450,850)
I estimated the height of rider after drawing up a 2d CAD stick figure(real human proportions) figure standing up while accelerating.

Then the mid height would be at about 575 as you said so we are both using the same calculating method(i think)

So at 600mm is not far fetched because the zerode bike pivot is at 580mm form the ground!

P.S Also Zerode must use the same calculating method

Also theres a way of putting the main pivot cc to the hub and gaining zero brake squat...pm me if you talk any further:)
I don't have my COM as high as that- I have it around about 1100mm (760ish above the rear axle for Linkage)

This would mean that the main pivot is about 320mm above the rear axle height (650ish above the ground) IMO too high to be practicable.

I will PM you regards the zero brake squat thing- I think I have an idea!!!;)