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DW LINK vs. VPP? Same or is one better?

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#21 ·
.WestCoastHucker. said:
doesn't the spring do the same thing?
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Yes, but wouldn't you rather not have to over-spring your bike so that the suspension is free to do its thing (absorbing bumps) rather than relying on a heavier spring to counteract pedalling/went transfer?

Speedub.Nate said:
I wouldn't say the dw-link resists weight -- that incorrectly imparts that pedaling forces act counter to suspension compression.
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After you said that, I went back to look at DW's old posts.
_dw said:
Plain and simple, dw-link counteracts mass transfer and pedaling forces during acceleration so that your rear suspension can freely absorb small and large bumps, while at the same time giving very little pedal feedback, and having excellent braking charateristics.
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_dw said:
In comparison to your Blur (which is still a very nice bike), the dw-link will also have more anti-squat, just enough to totally counteract mass transfer, but not enough to cause suspension extension.
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Does "counteracts mass transfer" mean something else than what I understand it to mean? I understand it to mean that when you pedal, it resists the weight transfer of the rider compressing the suspension.
 
#24 ·
flymybike said:
Spot on.
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I wish they had the :thumb: smilie here.

So pedalling forces do, to a certain extent, counter suspension compression. I guess the trick is to make it resistant enough to keep your weight from compressing it, but not so resistant to keep it from absorbing bumps, eh? Which would allow you to run a lighter spring, which allows the bike to be super compliant on small bumps.

MicroHuck, if you review _dw's posting history, there's a lot of suspension discussion.

http://forums.mtbr.com/showthread.php?t=4575
http://forums.mtbr.com/showthread.php?t=57727

All good, educational reading :D
 
#25 ·
binary visions said:
So pedalling forces do, to a certain extent, counter suspension compression.
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the magic word is 'anti-squat'. Its the same basic principal why low single pivots like to squat through every stroke, and high single pivots want to extend or jack (called 'axle-hop' in car terms). This extension can also be used to counteract the bodies downward forve on the bike through the pedal stroke as well, which is what he's talking about. The acceleration of the rear wheel vs the frame and how the two interact via the linkage is the major contributor to 'bob' performance.

So its a combination of anti-squat, chain tensions through the travel, IPs, suspension tuning etc that make the bike pedal and behave over bumps. Every suspension type will have different combinations, so yes, the links do matter.

And they are nothing like walking beams...
 
#26 ·
zedro said:
the magic word is 'anti-squat'.
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Right, I actually knew what the term was (believe it or not :D), just didn't want to chuck one more term into the mix.

I forgot to mention, but there's an extremely good description of what exactly the VPP design does and why it's different from DW-link in that first thread link I posted.
 
#27 ·
there is a great article on suspension types in the newest MBA magazine, but its mba so i dont know how much of it is true? :eek: dave weagle knows his stuff, i am looking forward to getting a IH sunday
 
#29 ·
binary visions said:
I forgot to mention, but there's an extremely good description of what exactly the VPP design does and why it's different from DW-link in that first thread link I posted.
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Thanks for pulling those posts up. I'm hoping Dave Weagle jumps in and posts some comments.

In that first post you linked to, Dave wrote: "The Hollowpoint's dw-link setup develops a tuned amount of anti-squat starting as soon as the suspension begins to compress. At 0 inches of travel through 2 inches of travel, the bikes basically develop 100% anti squat through a wide range of gears. This means that as you accelerate, the suspension action is left unimpeded to react to to terrain."

This is what I'd like him to clarify. My interpretation of this, and other stuff he's written (not to mention two years riding a Hollowpoint) is that 100% anti-squat is another way of saying the pedaling input forces have zero impact on the suspension -- it is neither compressive nor extending, just neutral.
 
#30 ·
bighitboy said:
there is a great article on suspension types in the newest MBA magazine, but its mba so i dont know how much of it is true? :eek: dave weagle knows his stuff, i am looking forward to getting a IH sunday
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I don't trust MBA for much in the way of technical writing. They'll rehash whatever marketing speak they can muster, but they've botched too many writeups and talked out of both sides of their mouths too often to be taken seriously.

There also appears to be some bad blood between MBA and either IH or DW. The other mags have given IH a fairer shake, but unfortunately they aren't great technical reviewers, either.

I know, I know, I sound like a conspiracy theorist. Bring on the German bike mags.
 
#31 ·
100% antisquat

Speedub.Nate said:
Thanks for pulling those posts up. I'm hoping Dave Weagle jumps in and posts some comments.

In that first post you linked to, Dave wrote: "The Hollowpoint's dw-link setup develops a tuned amount of anti-squat starting as soon as the suspension begins to compress. At 0 inches of travel through 2 inches of travel, the bikes basically develop 100% anti squat through a wide range of gears. This means that as you accelerate, the suspension action is left unimpeded to react to to terrain."

This is what I'd like him to clarify. My interpretation of this, and other stuff he's written (not to mention two years riding a Hollowpoint) is that 100% anti-squat is another way of saying the pedaling input forces have zero impact on the suspension -- it is neither compressive nor extending, just neutral.
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As I understand it, in the motorsports industry the standard opinion is about dead opposite to DW's. The suspension will be "unimpeded to react to the terrain" when you have 0% antisquat. Antisquat is an extending torque that combats the tendency of the vehicle to squat in the rear when accelerating. Having both a compressing and an extending force acting on the rear suspension at once (100% antisquat does just that) binds up and restricts the rear suspension.

I've attached a diagram of a motorcycle with more than 100% antisquat. I don't have a good one stored with exactly 100%. If the point identified as P of M, where the chain line intersects the swingarm line, were to lie on the lower of the two slanted lines running forward from the rear contact point, then you would have 100% antisquat.
 

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#32 ·
Speedub.Nate said:
I don't trust MBA for much in the way of technical writing. They'll rehash whatever marketing speak they can muster, but they've botched too many writeups and talked out of both sides of their mouths too often to be taken seriously.

There also appears to be some bad blood between MBA and either IH or DW. The other mags have given IH a fairer shake, but unfortunately they aren't great technical reviewers, either.

I know, I know, I sound like a conspiracy theorist. Bring on the German bike mags.
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I've seen MBA contradict itself in the same issue before. The issue at hand was lockout. At first they said pedal bob wasn't that bad, lockout was for idiots, then they sung its praises 30 pages later.

Their article about FSR/VPP/DW/Lawill all being the same did bring up a good point though -- they all have a similar design. The axle and brakes are mounted on a bar that is seperated from the frame by other links. All of those have at least that in common.

Personally I have my favorites:

FSR for XC
Single Pivot for DH/FR

In both cases, I just like the feel of the bike. FSR pedals really well too.
 
#33 ·
More on anti-squat

There are other theoretical problems with setting up a bike with 100% anti-squat. The percentage calculation is based on the assumption that the bike is accelerating steadily from a constant force. That never happens in cycling. Instead we have a sine-wave pattern of fluctuating force. At the beginning of a pedal stroke, when the force begins to increase, the bike is still decelerating. What happens is that the curve of the deceleration changes, going from increasing to decreasing. At this stage 100% anti-squat is way too much for efficiency.

And speaking of efficiency, the motorcycle text from which I got the diagram in my previous post says that maximum energy efficiency does not occur with 100% anti-squat (even assuming a steady acceleration). That's because the load shift will raise the front while leaving the rear unchanged. The net effect is that the center of mass is raised. If you have just enough squat in the rear to counter the raising of the front so that the center of mass stays level, then you have maximum energy efficiency.

Another consideration is traction. Because the anti-squat takes effect before the weight shift to the rear from acceleration occurs, the rear wheel is pushed down into the ground. This gives good bite, but it amounts to stiffening the spring, so it's bad for bump compliance. It's probably best to have around 100% anti-squat when climbing the very steepest stuff. But the DW-link bikes are set up with 100% in the middle gears. They have way more down in the granny with the largest cogs. On the other hand Horst type bikes like the Turners have about 100% when in their lowest gears.
 
#34 · (Edited)
Steve from JH said:
As I understand it, in the motorsports industry the standard opinion is about dead opposite to DW's.
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Without getting into another classic "dw suspension tutorial" I can assure you that that is an incorrect statement. The analysis that I use, and infomation used to describe the systems is 100% accurate, and agreed upon by the common text and people that I have dealt with in the motorcycle industry. I had the great opportunity to sit with Tony Foale last fall, and his analysis and nomenclature agree with mine fully.

Steve from JH said:
The suspension will be "unimpeded to react to the terrain" when you have 0% antisquat.
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incorrect statement, actually the reverse is true. since squat of any type only occurs under acceleration (positive or negative) 0% anti squat would allow the suspension to compress, therefore loading the suspension. I think that it is pretty obvious to any rider that your suspension will absorb small bumps easier when the suspension is not compressed versus compressed. Its gets deeper than that, but you should be able to see the reality of it.

Steve from JH said:
Antisquat is an extending torque that combats the tendency of the vehicle to squat in the rear when accelerating.
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correct statement, sort of. Anti squat is not a toque, its a resultant force, otherwise correct.

Steve from JH said:
Having both a compressing and an extending force acting on the rear suspension at once (100% antisquat does just that) binds up and restricts the rear suspension.
Click to expand...
incorrect statement

Steve from JH said:
I've attached a diagram of a motorcycle with more than 100% antisquat. I don't have a good one stored with exactly 100%. If the point identified as P of M, where the chain line intersects the swingarm line, were to lie on the lower of the two slanted lines running forward from the rear contact point, then you would have 100% antisquat.
Click to expand...
yes, you would, at that instantaneous point in the suspension travel. The anti squat amount will drop rapidly in this suspension layout.

Hope this clears some things up
 
#35 ·
Steve from JH said:
There are other theoretical problems with setting up a bike with 100% anti-squat.
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I agree somewhat. Thats why I invented dw-link. The flip side to consider is that a suspension using a constant 100% anti-squat will outperform one using a constant 0% anti-squat no matter what.

Steve from JH said:
The percentage calculation is based on the assumption that the bike is accelerating steadily from a constant force. That never happens in cycling. Instead we have a sine-wave pattern of fluctuating force. At the beginning of a pedal stroke, when the force begins to increase, the bike is still decelerating. What happens is that the curve of the deceleration changes, going from increasing to decreasing. At this stage 100% anti-squat is way too much for efficiency.
Click to expand...
Squat is a function of acceleration. As the acceleration varies, the squat amount varies. Its a non-issue.

Steve from JH said:
And speaking of efficiency, the motorcycle text from which I got the diagram in my previous post says that maximum energy efficiency does not occur with 100% anti-squat (even assuming a steady acceleration). That's because the load shift will raise the front while leaving the rear unchanged. The net effect is that the center of mass is raised. If you have just enough squat in the rear to counter the raising of the front so that the center of mass stays level, then you have maximum energy efficiency.
Click to expand...
You are misinterpreting your text.

Steve from JH said:
Another consideration is traction. Because the anti-squat takes effect before the weight shift to the rear from acceleration occurs, the rear wheel is pushed down into the ground. This gives good bite, but it amounts to stiffening the spring, so it's bad for bump compliance.
Click to expand...
No, not really. I see what you are thinking, but you are missing a key point. Perform a simple dynamic analysis and you will see how the ofrces actaully lay out. The wheel force is the same either way, just the suspension ride height and actuation force changes.

Steve from JH said:
It's probably best to have around 100% anti-squat when climbing the very steepest stuff. But the DW-link bikes are set up with 100% in the middle gears. They have way more down in the granny with the largest cogs. On the other hand Horst type bikes like the Turners have about 100% when in their lowest gears.
Click to expand...
I can tell for sure that you have not mapped out the dw-link bikes, or you are not understanding how they work. These statements are just not true for any of these bikes. Sorry to call you out, its not my intention to make you look bad or anything like that, I just have to be honest.

All the best

Dave
 
#37 ·
How to prove what the common opinion of suspension experts is? Obviously readers of MBTR are more likely to believe you than me. And I don't even count myself as a suspension expert.

For what it's worth I just typed in "anti-squat" at the top of my screen and got a response from AOL's search engine. Choosing the first entry that looked helpful on the first page I found the following statement:
So to answer the question as to what increasing anti-squat will do. It can assist in incautiously creating forward bite. But just for an instant, and then will go away. This might seem like it will help rear grip, and is some specific cases it will. However, this instantaneous transfer (geometric stiffening) comes at a cost of decreasing the rear compliance of the car which in the long run , can often hurt rear bite.​
That "geometric stiffening" is what I was talking about. With 0% the spring remains unstiffened. Now if it compressed a lot from the acceleration, not much travel would be left, and the shock rate might be higher, and those would be undesirable results. But the small movement produced by puny human acceleration should leave the spring free to react the same under power as coasting.
 
#38 ·
Steve from JH said:
How to prove what the common opinion of suspension experts is? Obviously readers of MBTR are more likely to believe you than me. And I don't even count myself as a suspension expert.

For what it's worth I just typed in "anti-squat" at the top of my screen and got a response from AOL's search engine. Choosing the first entry that looked helpful on the first page I found the following statement:
So to answer the question as to what increasing anti-squat will do. It can assist in incautiously creating forward bite. But just for an instant, and then will go away. This might seem like it will help rear grip, and is some specific cases it will. However, this instantaneous transfer (geometric stiffening) comes at a cost of decreasing the rear compliance of the car which in the long run , can often hurt rear bite.​
That "geometric stiffening" is what I was talking about. With 0% the spring remains unstiffened. Now if it compressed a lot from the acceleration, not much travel would be left, and the shock rate might be higher, and those would be undesirable results. But the small movement produced by puny human acceleration should leave the spring free to react the same under power as coasting.
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Comparing apples to oranges?

You need to get off your high-horse and quit disagreeing with dw, who obviously understands this far more than you do.
 
#39 ·
_dw said:
Squat is a function of acceleration. As the acceleration varies, the squat amount varies. Its a non-issue.
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During pedaling there is alternate negative and positive acceleration. The negative acceleration can be thought of as acting at the center of mass and therefore produces no load shift either way. The pedal stroke starts increasing in force while the bike is still decelerating and there is no squat or jack from the deceleration.. So the extending anti-squat force initially has no accelerational load shift to work against.

You are misinterpreting your text.
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Here is the text:
We can imagine a particular case in which there is zero jacking; this would only come about when the front end extension is exactly equal to the rear end compression, or rather, to state this in scientific terms, when the two axes have equal vertical stiffness in opposition to the force of traction.​
This would give rise to a rotation of the motorcycle around its center of gravity without any variation in center of gravity height.​
The course described by the center of gravity when the motorcycle is under acceleration will be practically horizontal in this case, which means minimum waste of energy.​

I can tell for sure that you have not mapped out the dw-link bikes, or you are not understanding how they work. These statements are just not true for any of these bikes. Sorry to call you out, its not my intention to make you look bad or anything like that, I just have to be honest.
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It's hard to map using my primitive Linkage freeware and not knowing exactly where the pivots are. The best I can come up with is that the Mark III, in both middle and small ring, at a sag of either 30 or 40 mm, keeps the chain line running through the center of curvature throughout the first half or so of travel. That's an interesting achievement but I don't understand how it's an advantage any more than keeping the chainline through the IC a la Ellsworth.

I calculate the anti-squat at about 135% using a center of mass at 1 meter high. That's about where my crotch is when I'm sitting on my bike. To get 100% anti-squat the CM would have to be up by my chest.

I'm not worried about being made to look bad. I'm old enough to be your grandfather and nothing much bothers me and I couldn't look much worse.
 
#40 ·
TheSherpa said:
Comparing apples to oranges?

You need to get off your high-horse and quit disagreeing with dw, who obviously understands this far more than you do.
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Are you referring to the high BB on my Id?

What I was just doing was quoting people who disagree with DW.

By the way I would definitely choose a dw-link over a vpp.
 
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