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Discussion Starter · #1 ·
This is a question for Derby, DW, or anyone else with both DW Link and general suspension expertise.

I have read many of Derby's and DW's comments on the superiority of the DW Link but remain confused.

In viewing the animation of the 2005 MKIII using Linkage v2.5, it would appear that the largely rearward axle path of this bike results in pedal kickback of up to 21 degrees in the 36/16 gear combo. The kickback declines to a maximum of 16 degrees in the 44/11 combo, but rises to a whopping 36 degrees in the 22/16 combo. These figures assume that only the rear wheel is moving. When you factor in the movement of the front suspension, which results in a forward pivoting of the bottom bracket, the overall feedback rises even higher. I fail to understand how the DW Link can be justified as superior when many other suspension designs demonstrate far less feedback. Are we dealing with a tradeoff here between bob and feedback? If so, this would represent simply a different type of good design to me, not a design that's superior to everything else.

Furthermore, my understanding is that the DW Link reduces bob by using the chain tension created by pedaling to push the rear wheel in a direction (rearward) opposite the direction that results in compression of the suspension--at least, the DW Link does this during the first part of the rear axis's travel. This process, almost by definition, would indeed seem to reduce the compression of the suspension that we know as "bob." However, while the rider can observe his spring and smile at the lack of movement, is he really saving his body's energy? It would seem to me that the rider is wasting energy on driving the rear wheel backwards--and perhaps even excessively downwards on hardpacked terrain--instead of driving the whole bike forwards as much as possible. In other words, the lack of bob may be true, but at least some of the gain in efficiency may be an illustion. A bike that keeps the wheel vertical during initial travel and that has a pivot placed in a manner so as to reduce the opportunity for the rider to lift the rear merely by pedaling would seem like it would offer superior efficiency.

Derby, if you respond, it would be interesting to know your affiliations, if any, as well. Are you a champion of the DW Link simply based on your analyses, or are you affiliated with Ibis or Iron Horse in any way?
 

· mtbjk
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The Real Deal

Simply just a few words. Its the real deal, It just works, Better than any other design out there. Dont know if you have had the opurtunity to ride one but you need to throw a leg over one and take it for a ride, Make sure suspension is set to proper sag and go hit the gnarliest trail you can find and experience it for yourself. and if that doesnt do it, go for a good long climb. Just cant explain but it just works and you do not feel any bob in the suspension, Im not going to say there isnt any but it definetly is not naticible as many others are, and as far as pedal feedback, I have ridden a dw link bike for over 3 years and still dont think I have felt any and ride in alot of differant gear combos in differant terrain's and again I cant say enough but it does just do everything it claims. (the real deal)

Ride On
Jan R
 

· www.derbyrims.com
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You just have to ride one.

The change or fluctuation in chain tension rate during travel movement with the pedal cadence speed is what produces noticeable pedal feedback. Although the dw-Link path compresses rearward in length from the bottom bracket nearly all of travel, the chain tension rate during travel is very constant. The fluctuation of tension rate during travel is nearly the same as a bottom-bracket-concentric monopivot, nearly none. Like the BBC monopivot the dw-Link is only mildly fluctuating in tension rate dependant on gear ratio. It’s possible that the dw-Link has less pedal tension fluctuation in the lower gears than a BBC monopivot, it swallows bumps while climbing in the granny like no other I’ve ridden including high or low pivot URT (Universal Rear Triangle).

The rearward path is a factor of leverage. The gear rate is a factor of leverage. The rider position and direction of pedal input is a factor of leverage.

With minimal pedal feed back the dw design has leverage that is balanced for acceleration, like a runner leaning forward at the starting block and while running. Or like a BB concentric monopivot, a design can have less than balanced acceleration; the same runner isn’t leaning so far forward. With the same start, the runner leaning more forward will leap forward with each stride; the runner leaning less forward will hop in the air more with each stride.

On a bike hoping up and down when pedaling creates bob and less forward directed energy for acceleration. Riders can find a cadence pace for a bike that bobs that minimizes bob, more so while seated and spinning moderate input, but difficult to control bob while standing or accelerating hard. Damping, hydraulic drag, can lessen or deaden the vertical hopping bob direction, but the rider energy is partially spent as damping fluid heat but not as much forward direction, and firmer damping produces less bump compliance when coasting or braking than well aimed rider balanced leverage using minimal damping.

This is just an educated guess of how the difference of the dw-Link is compared to other common very low pedal feedback designs. I’ve ridden a lot of the current designs including the dw-Link, Marin/Whyte, VPP, I-Drive, ICT, FSR, Rocky Mountain 4-bars, Horst-link, soft-tail, monopivots and URTs, earlier this decade before platform dampers were produced that hid the higher bob characteristics of the lower pedal feedback designs. Anyone who started riding full suspension after 2003 has no concept of the additional smoothness and traction potential of riding without platform damping.

I demo rode the dw-Link before I knew it was something special, when the first dw-Link Hollowpoint was produced. I expected it to ride something like the quick accelerating Schwinn Rocket 88 I’d test ridden, and it was quick accelerating but it had a more swallow the bump while pedaling feel like a low monopivot or very similar pedaling ICT which bobbed quite a bit before good platform damping was available. Now days with more travel, the dw-Link rides with just as efficient power to weight acceleration as the first version and swallows bumps even better.

You just have to ride a dw-Link with minimal compression damping to discover what is possible with rear suspension.

I have no commercial affiliation with any bike product or company. Everyone I’ve met and corresponded with from Iron Horse, Independent Fabrications, Ibis, and Dave Wengle have been super friendly and have given me demo rides when possible and tuning advise. I get no swag or free-bees. I bought my dw-Link bike for full suggested-retail price after long research.
 

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WheelsForHeels said:
It would seem to me that the rider is wasting energy on driving the rear wheel backwards--and perhaps even excessively downwards on hardpacked terrain--instead of driving the whole bike forwards as much as possible. In other words, the lack of bob may be true, but at least some of the gain in efficiency may be an illustion.
I wont pretend to understand the mechanics of the DW-link but I do have a basic understanding of physics and that statement I've quoted above doesn't make sense.

If energy is going into driving the wheel down or backwards but the shock isn't moving (i.e. not bobbing) and the ground is flat "hardpacked terrain" then the rear wheel isn't moving down - the only movement is the bike going forwards. hence it would be very efficient - the energy can't just disappear.
 

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When I ride my MKIII 05 There is only one time I notice pedal kick/feed back. Its a pretty odd trail feature on my local trail:
Fairly steep climb with a small drop off on it I would say a little under a foot of drop and you land back on a steep climb. Im usually in first gear (26-32) I I do notice a little pedal kick in this moment.
It is the only time I have ever notice anything like it on the DW link and it is pretty insignificant. IMO the MKIII is the best allround bike available.
 

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Discussion Starter · #8 ·
Hmmm...

It's interesting to hear from everyone that the experience of pedal feedback is minimal. Derby, thanks for your technical explanation too; you clearly put a lot of thought into it. But I'm afraid I don't fully comprehend it. Could you explain explain more fully what you mean by fluctuation in "chain tension rate?" Normally, I read about fluctuation in "chain length" (which is a fact with the DW Link bikes) as the major factor in pedal feedback. You seem to consider fluctuation in chain tension rate more important than fluctuation in chain length, so it would be great to know exactly how you define the former and why you think this concept is key to feedback.
 

· www.derbyrims.com
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WheelsForHeels said:
... You seem to consider fluctuation in chain tension rate more important than fluctuation in chain length, so it would be great to know exactly how you define the former and why you think this concept is key to feedback.
That's a good question. I don't have an exact answer. The dynamics of mountain bike suspension are very complex. Simple theories are just hype or wishful thinking.

We expect increased resistance when pedaling in bumps. While coasting on a flat smooth surface, then hitting bumps, we expect the bike to slowed by the bumps. When pedaling we expect pedal resistance to be greater in bumps.

Like different spring types, rate of increase in leverage resistance at the pedals can be rising or falling or flat (linear). If the rate changes quickly from falling rate (becoming easier) to rising (becoming harder), the rather constant rider pressure feels the resistance change, or "kickback" or "feedback". A rising rate of pedal resistance during compression travel becomes falling rate during rebound.

The dw-Link maintains a close to flat rate of increased pedal leverage resistance climbing or accelerating in bumps. The rider's legs feel this as a smooth expected constant resistance. Other low feedback designs have smooth increased, near constant resistance. But the dw-Link leverages the rider forward more, rather than up and down with the same pedal input power, both on smooth surface and bumpy.

There are many more micro leverage balance changes during travel. Such as chain angle off the sprockets, bump face contact with the wheel, momentum of inertia. I couldn't begin to put all the angles and tensions together. I imagine DW can generate the math in detail from the computer solid modeling program used to design the suspension geometry. There is no special theory, just physical modeling and rider feedback behind the design.

The dw-Link has a very digressive rate of anti-squat balance. There is just enough to accelerate the bike without pedal bob near the 20 - 30% sag area (depending on use). And the anti-squat balance is rapidly reduced as bump travel compresses the suspension deeper. No other design previous to DW's had such a digressive tension rate during compression.

This dynamic anti-squat resistance rate during travel is integral to the lack of pedal feedback.

This is rate of anti-squat is claimed in the most resent patent. There is detailed explanation and graphs for the anti-squat rate:
http://patft.uspto.gov/netacgi/nph-...7,128,329.PN.&OS=PN/7,128,329&RS=PN/7,128,329
 

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yogreg said:
My head is going to explode with all this....

Demo a Dw-Link bike and all will be explained in the ride.
Agreed!!

I have a loaner/demo 06 MKIII from a buddy at WWC. I took it for a two hour rooty, twisty ride yesterday & was absolutely sold, 100%. Now I need to get one, period.

Go try one.

DP
 

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Ride One

I rode every bike I could get my hands on before deciding on my bike. I ended up with an Azure that I love to ride. Iron Horse was not on my original list but I decided to try it out at a festival. I also rode a Specialized Stumpjumper FSR, Cannondale Prophet, Titus racer-x, Trek Fuel, and a few others. Got a great deal on the Azure and have been riding it 3 or 4 days a week. I know it was the right decision.
 

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Discussion Starter · #14 · (Edited)
rate of increase in leverage resistance

Derby, you make some interesting points. I find your explanation of anti-squat balance to be somewhat compelling, although I don't see how one suspension setting could acheive "just enough" anti-squat balance through a range of torque inputs (ie, gear choices and levels of pedal force) to the chain. It would seem to me that "just enough" in one gear on one terrain would be too much or too little in another. But that aside...

What I don't find compelling at all is your argument that the DW Link has a flat rate of increased pedal leverage resistance. That's an intersting idea, but let's do a thought experiment: Imagine that a rider with 6 inches of rear suspension travel is pedaling at constant speed over a large rock--not an uncommon situation for an all-mountain rider. The first inch of the path over the rock has a gentle incline of, say, 20 degrees. But the next inch of of the path over the rock has a steep incline of, say, 80 degrees. When the rider's rear wheel hits the first inch of the path, the chain will grow at relatively slow rate; but when the rear wheel goes over the next inch, the chain will grow at a faster rate due to the greater vertical travel required for an equal amount of movement over the surface. Thus, when the rear wheel is going over an irregularly inclined surface--which is typical of "bumps" found in natural-terrain--chain growth rate will be irregular as well. In fact, a typical craggy boulder or rocky, rooty hill with numerous, fast changes in degree of incline could produce continual, rapid changes in chain growth rate, it would seem. So even if your suggestion that riders are only sensitive to changes in chain growth rate (as opposed to change in chain length) is correct, I would question your notion that there are no changes in chain growth rate in real-world situations. The real world, as we know, is a jagged place, not a place whose terrain features were drawn into existence with a straight-edged ruler.

Of course, my thought experiment above could be challenged in various ways. For example, you might argue that the rider is not actually going at constant speed as he goes over the rock. You could say that as the rider goes over the steeper section of the rock, he either slows down or pedals harder. But it would seem to me that the change in chain growth as the rider transitions from the gentle incline to the steep incline would contribute to this situation, forcing the rider to pedal harder to counter the chain growth or face a greater slowdown in speed than the rock would force by itself. And not only would chain growth occur, but changes in chain growth rate would occur, which might activate the rider's sensibilities.

Thanks for the link. I have bookmarked it and will check it out later.

WheelsForHeels
 

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Discussion Starter · #15 ·
Will demo soon

By the way, to everyone suggesting that I do a demo, I'm working on it. Trying to get a six point to try in the NYC area. Will be interesting to compare the ride to the suspension ideas... Glad you all like your rides. I have to say the new models from Iron Horse look incredible.
 

· Blanco
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derby said:
Like different spring types, rate of increase in leverage resistance at the pedals can be rising or falling or flat (linear). If the rate changes quickly from falling rate (becoming easier) to rising (becoming harder), the rather constant rider pressure feels the resistance change, or "kickback" or "feedback".
Are you sure about this? High single pivots (famous examples: Bullitt, AS-X, Heckler) have a basically linear increase, and pedal kickback is extremely obvious when riding them. It seems to me like the absolute amount of kickback through the part of the suspension travel you are using is much more important than the shape of the curve (for any existing, reasonable suspension design).

According to Linkage, at 32/15 an AS-X has roughly 2.5x the pedal kickback of a 7point. At 22/34, this drops to slightly under 2x. Interestingly, a BigHit, which has negative pedal kickback in higher gears and almost zero at 32/15 has almost 2/3 as much as the 7point in 22/34.
 

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WheelsForHeels said:
Just came back from a 2.5 hour ride on the Cannonball trail in Ringwood, so you need not fear. There's a time for the body, and a time for the mind.
I'm jealous. I spent 2 hrs on the MkIII yesterday & was dying to get out there today.
Unfortunately, I think we had near record rainfall & SUPER high winds overnight & this morning. So here I sit.......surfing....... :madman:

DP
 
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