dw-link / Turner damper testing

On Thursday night of last week, I headed off to sunny Murrieta, California (about a 9 hour trip across the country for me) to finish up some suspension testing with Turner bikes. Dave Turner and I wanted to try to get all of the FOX damper tunes that we have been playing with finalized for the big On-Dirt Demo at Interbike. This is where the Turner Bikes faithful will get to ride the new dw-link bikes for the first time. (note: if you are a rider and want to get out and feel the bikes for yourself, this is the place. dw-link bikes from Ibis Cycles, Pivot Cycles, Turner Bikes, and Iron Horse will be there and ready to ride. I'll personally be at the event under the IBIS, Pivot, and Turner tents on the 23rd to answer any questions that riders might have. Plus, I'll be there to ride!

This is the type of testing that I o with all of my suspension licensees, sometimes in person (like when I flew to Arizona to visit Pivot Cycles in July (pre-blog, sorry!)) and quite often here on my home trails.

Typically we would have been joined for our suspension testing by one or two representatives from our suspension partner FOX Racing Shox, but this time, most of their staff was attending the World Cup downhill finals in Schladming, Austria. We invited along two well known locals for our second day of testing, our friends Chris Lesser and Alan Davis, both of bike magazine. We rode on their local trails, a mix of climbing, square edge hits, fast off camber turns, and very little traction. This was the perfect place to really feel out the differences in traction and compliance between different setups.

This type of testing is a little different than your normal ride. We usually work on short loops of trail, testing different settings and noting the riding perceptions for each test while we switch out shocks or settings. We switch bikes frequently and talk through each detail as carefully as we can. For some sections of trail we use a spotter to observe suspension action, and on other sections the rider observes on their own. We look for specific suspension traits which can vary depending on the bike, setup, or test. It's quite a bit more work than your average ride.

Chris, Dave, and Alan posing with the new Turner 5-Spot



The new 5-Spot, 140mm of trail eating travel



Talking about the "feel" of the bikes and the settings changes that we tested on the last run.


We ended up working on 3 bikes during our two days of testing.

On the first day, Eric from Turner, Dave Turner and I dialed in the new 100mm Flux's damper settings. The bike was designed to use either the small or large air can Fox RP23 shock. Our FOX RP23's were the 2009 spec, with light compression and light rebound settings. This particular shock has a lever that can actuate what FOX calls "Propedal". Propedal is essentially a low speed compression increase that can be actuated by the rider by flipping a lever on the shock. With a separate setting on the shock, the rider can choose between 3 levels of Propedal that will kick in when the lever is flipped, with level 1 being the least amount of compression damping, and level 3 being the highest. We found that our bikes had the best traction in all riding situations with the Propedal lever turned off, as is usually the case with dw-link bikes. We did specific testing to assess how well Propedal could help on standing climbs. We found that the best traction was had with the Propedal lever in the off position, and that for riders who really "mash" out of the saddle that level 1 could control their excess body movement with only a small traction compromise. Levels 2 and 3 provided no benefit, but less observed climbing traction (more wheelspin) during testing. (keep in mind that many bikes use a LOT more compression damping than the dw-link, and the traction loss with higher levels used on other designs is immediately noticeable.)

We will work on dialing in other shocks including the Rock Shox Monarch over the next couple of months. Additionally, Darren Murphy from PUSH Industries took the time to send over a couple of specially tuned RP23's that were designed with special valving that really lets the dw-link take full advantage of available traction. These special valved shocks are nearly unusable on other suspension designs, but the dw-link with it's position sensitive anti squat can run a significantly more compliant shock setup than other designs. The proof is in the ride, and the ride, compliance, and traction were amazing for a 100mm travel bike.

On the second day we tested the Flux again, along with the 5-Spot (140mm travel), and Sultan (29" wheel 120mm travel).

Chris Lesser was a sport and rode the 29er' hard for us. Wheel rate wise the Sultan is in between the 5-Spot and Flux. It has XC feel, with long travel trail bike compliance and a little end travel ramp to soak up the big hits. We knew what to expect with the Sultan, and there were no surprises. It rode just like a 5" trail bike, with all of the advantages and peculiarities of a 29'er. Shock setting wise, we liked the XV air can on the RP23. We preferred the Propedal off for all conditions, and one thing we observed was how planted the rear tire was on the standing climbs without extra compression damping. The dw-link was really working quite well on the Sultan, just taking advantage of that big contact patch. It was pretty cool watching it work, and I couldn't help but to feel psyched to see it doing exactly what it should. Like the Flux, for riders who really mash the pedals, Propedal 1 will work, but it would probably work better for riders like that to work on form and take the traction instead. To each his own though!

The 5-Spot is a uniquely cool dw-link trail bike. It was really designed to use the XV RP23, which in the 190mmX51mm size features a very low air spring compression ratio. We designed a bit of ramp into the wheel rate, and the leverage rate stays progressive throughout the travel. This makes the suspension really compliant early in the travel, with a little spring ramp in the end and a nice controlled damped feel at the end of the travel. It hooked up hard in the corners and soaked up the little drops around the trail with ease. We preferred the Propedal off for all conditions, even for standing climbs. Like the other bikes, real mashers could use setting 1 for the standing climbs, and settings 2 and 3 should probably be avoided. I am looking forward to testing this bike with a coil-over shock, I think that it is going to really work out nicely.

Darren from PUSH worked his magic on a shock for the Spot too, and as expected, it was also brilliant. That dude knows what's up when it comes to damper tunes.

OK enough blogging for today, more tomorrow.

Suspension Terminology 1: What is Wheel Rate etc..?

Quote:

Question from Interested Rider Thanks, this is still far from clear: Quote: Originally Posted by _dw Designing specifically for wheel rate basically allows for a wider range of tunability with the stock shock settings, and it has the additional benefit that damping does not need to be specifically adjusted to make up for uncontrollable issues that arise when leverage rate is not matched with the air spring curve. All in all the method provides more shock tuning options with less tinkering. Quote: Originally Posted by _dw Through experience, I've learned how to very precisely tune wheel rates, and for air shocked bikes, this is really important. Each bike's leverage rate is specifically engineered to work with a specific air shock and even air can volume to hit a desired wheel rate or wheel rate options. From there we develop damper tunes to meet the frame requirements. :confused:

Some terminology will probably help..

Wheel rate:

Wheel rate is defined as the change of wheel load at the center of tire contact patch per unit vertical displacement of the sprung mass relative to the wheel, at a specified load. - Maurice Olley, Chassis Design Principles and Analysis; ISBN 0-7680-0826-3

(this does not factor in tire and wheel deflection, there is a different term and calculation for that)

So in layman's terms, wheel rate is the force change at the tire to ground contact patch as the suspension cycles through its travel. It can be graphed as force at the tire versus displacement of the suspension. Wheel rate is the force increase that you feel in your feet and your seat as you sit on your bike and compress the suspension.

I like to use the term "feel" to describe the human perception of wheel rate when riding a suspension bike or motorcycle. Heck, why not define it.. just to be clear.

Suspension "Feel": The human perception of wheel rate and other suspension characteristics through a vehicle's interfaces. On a bicycle these interfaces include the seat, pedals, and hand grips.

Air Spring Curve:

An "air spring curve" is the graphical representation of spring rate for an air spring. Spring rate is understood by most people who have taken a high school level physics class. It can be measured as spring force output versus spring displacement. (I use displacement as the term for length change because it is shorter and non-denominational). Where metal coil springs typically feature a constant rate, an air spring typically has a non-constant rate. This non-constant rate provides challenges for a suspension designer, particularly one like me who is trying to engineer a specific wheel rate, or "feel" into suspensions.

Leverage Rate:

This is one of those terms that rolls easily off the tongues of many bike people, yet few actually understand the nuances of how it can- and why it should be manipulated to benefit a suspension bike.

Leverage rate (or more accurately Instantaneous Leverage Rate) is the measured ratio of wheel displacement versus spring displacement at any instantaneous point in a suspension's travel.

This is not to be confused with Average Leverage Rate, which is just a straight division of total wheel displacement versus total spring displacement.

In order to achieve a specific wheel rate (remember, this is the suspension "feel" that I defined earlier), I need to make sure that my leverage rate is designed to specifically account for the shape of the air spring curve. This is just one of several parameters that must be considered. Additionally I spend a great deal of time looking at damper force outputs and anti-squat / braking squat. Those are discussions for another day.

As interested readers of this blog delve into this subject deeper on your own, you will notice the amazing variety of leverage and corresponding wheel rates used in cycling today. From there perhaps you will ask, "why is one more useful than another"?

I'm on my way to California for some spring damper testing, so I've got to cut this short. Thanks for reading and I hope this is somewhat educational!

What is anti-squat and why is it good?!!

Anti-squat in suspensions has become a focal point for cycling suspension designers recently. The term is beginning to become more "en-vogue" for cycling marketing, and I imagine that in a few years, it will be one of the main points discussed in marketing brochures. A good deal of this is partly due to the success of my dw-link suspension, which is a position sensitive anti-squat design, the first of its kind.

Over the years I've been asked "what is anti-squat" hundreds of times. A lot of times I've been asked that question by people with their own preconception on what it is or how it works. This makes explanations challenging at times, but not impossible, just longer winded. I'm not the best at oversimplifying, I tend to think that every detail in necessary in a discussion, and this has not helped me to publish simplified accounts of how the dw-link works. After all, it's not simple at all! I have been working on breaking it down.

One of the incorrect preconceptions that I frequently hear is that more anti-squat somehow equals less traction. Actually, the opposite is the truth. The closer a suspension is to being balanced, the more traction it can deliver at the wheel.

Anti-squat and the concept of squat in general can be difficult to grasp sometimes. As its core, squat is a suspension's reaction to mass transfer that happens during acceleration. Anti-squat is a term for a force that balances the suspension's reaction to mass transfer.

100% anti-squat is the exact amount that a suspension would need to develop to completely counteract the effects of mass transfer. One way to simplify this relationship is to think of it like an old style weight balance. More than 100% anti-squat would overbalance the suspension, and the suspension would extend under power. Less than 100% anti-squat would underbalance the suspension, and it would be allowed to compress under power. pro-squat (negative anti-squat) (and yes, some well advertised bikes actually feature this) not only allows the suspension to compress under power, it forcibly compresses the suspension while accelerating. Any amount of pro-squat is about the worst case scenario from an efficiency and traction standpoint.

On one side you have mass transfer loading up the suspension. On the other side, you have a balancing force. There are three approaches used in cycling suspensions today that one could take to balance (or not balance) out this mass transfer.

1) you could do nothing. The suspension would compress with every acceleration and subsequent mass transfer, and with every compression stroke and rebound stroke of the shock, you will lose energy. Your wheel rate rises as the suspension compresses, and your suspension is now stiffer with less compressive travel. Your suspension is at a disadvantage to absorb bumps. Traction decreases.

2) you could use a shock with a great deal extra low speed compression damping. The suspension would compress less than the first case with every acceleration and subsequent mass transfer, but still some, every time your shock compresses or rebounds you lose energy.

-a little bit of basic damper theory-

Keep in mind, that in order to support the mass that has transferred to the rear wheel under acceleration, the shock needs to develop force at the damper shaft. A damper develops force by pushing oil through a small orifice. As the oil in the damper is pushed at high pressure through the small orifice, the shearing force in the oil causes friction and energy is converted to heat and dissipated. The more resistance in the damper, the higher the shearing force, and the more energy is converted to heat and dissipated.

Here is the worst part. Now your suspension is unbalanced when you are cornering or not accelerating under power.

Think about it, your compression damping is raised to deal with the additional forces of mass transfer due to acceleration. When you are not accelerating, that mass transfer does not exit, and there is less force that the shock needs to deal with. Your shock is now overdamped when you are coasting. Most of your cornering happens when you are coasting, so effectively you have unbalanced your suspension for cornering. Traction decreases in all cases.

Note: Some people take this to mean that an ideal is absolutely zero low speed compression damping. This is not the case. Low speed compression damping is of paramount importance to a properly set up suspension, but like many things, too much is not good for you..

3) you could use anti-squat. This would allow the suspension to react to mass transfer only during acceleration. The closer a suspension is to operating at 100% anti-squat, the closer to being perfectly balanced the suspension is. The closer to balanced the suspension is, the MORE TRACTION the suspension has in all conditions.



In short, a position sensitive anti squat, with a higher level of anti-squat gives MORE TRACTION than any other approach, and especially more traction than approaches using less anti squat. Today dw-link is the only suspension system that features approach 3.

More to come soon.

New bikes, so many good ones to choose from, so little space in the shop!

I'm not sure what bike I am most excited about.

The DHR for sure is up there on my list. I'm a downhiller by passion and this bike incorporates what I think are some of my best ideas ever. While most of the industry has been chasing and benchmarking the dw-link Sunday design, in reality I moved beyond that bike in my mind 3 years ago. I knew what I wanted to do for the next evolution of a dw-link DH rig, and the new DHR's suspension is that evolution. I hope that I've raised that bar ever higher, and based on what I have seen of other new bikes to the market, I feel like my contributions will help to do the Turner name proud.

The 5-Spot is a legendary bike in the Turner line. I've spent time on one already it's an amazing bike. The thing is, I already have TWO other amazing 140mm travel bikes, my Ibis mojo and Pivot Mach 5. I ride those 2 bikes interchangeably all the time. I also have my MKIII that I put a lot of miles on. Do I have the need for another 140mm bike? No, absolutely not. Do I want a 5-Spot anyways? You bet I do! Who wouldn't! I think that this one is a no-brainer, I'm going for it.

Ahhh, the Sultan. 29 inch wheels. I've got to say, I didn't really WANT to like 29 inch wheels. It's not that I have anything really against them, but man, I already have too many trail bikes!

Well, I went to do some shock testing with the guys at Pivot Cycles (www.pivotcycles.com)and rode their new 429. It's a 100mm bike, a little shorter travel than I typically like to ride, but MAN WAS IT FUN!! I loved it. The trails that we were on were pretty wide open and fast, lots of ups and downs on harder pack. That bike ate it up, it was just FAST! I'm really looking forward to riding the Turner with its 120mm of travel. That should be interesting on the trails. I'm not sure about how its all going to work out in the twisty East Coast woods, but I'm ready to gove it a try.

Last but not least, the Pivot 167mm bike and Turner RFX. Two long travel trail bikes made to climb and eat up the big stuff too. I already know that the Pivot 167mm bike is awesome. I've spent some time in Arizona working on shock tuning ad spec and this bike is really capable. One thing that stands out on the Pivot as compared to other 160+mm travel air shock bikes that I have ridden is the noticeable lack of "hammock" in the middle of the travel. This is an area that I concentrated on with the design of the kinematics and I was really happy to have achieved our goal. I can't wait to get on that RFX and put it through the paces! I have high expectations.

It's a huge day in dw-link world! (Turner content)

Well, today is a big day in dw-link history, one of the biggest actually.

For months, riders have been asking and wondering who the next dw-link licensee will be. There has been almost giddy anticipation on the mountain biking forums that I peruse. This is how crazy it's gotten; With so many posts on the subject, even I have felt a little uncomfortable at times, and I think that a few readers have gotten so sick of seeing the title that they actually may resent me a little somehow! (Its not my fault that people are fired up, I swear!!) :)

SO, Anyways. I am so happy to report that the one and only Turner Bikes (http://www.turnerbikes.com/) is the fourth and newest dw-link licensee. We have been working on this collaboration for a long time now and finally we get to show the world what we have been working on. I am really excited about the new bikes, I can't wait to have a couple production models in my stable.

I went to the MTBR.com Turner forum to see what people thought of the lineup. I was astounded to see that there were 631 people! viewing the forum at one time. That is ridiculous, typically if a forum breaks 200 people that's a huge number. To say that I am stoked for Dave Turner is an understatement. He is one of the nicest and hardest working people that I have ever met. If the interest in his new bikes is any indication of how support for the brand will be this year then he will have a great year. He deserves it! I am so happy to be a part of helping him out with that.

Take a look at their website to see the new bikes, I hope that you like them!

I need to figure out how to get some pictures into this blog, but first, I'm going to go for an XC ride.

The dw-link blog is alive!

Hi!

My name is Dave Weagle, and this is my first blog post. Ever. I've been wanting to do this for years, but really, the task of setting up a blog just seemed so huge and time consuming. Thanks to my wife however, I now see how silly that was.

I've wanted to start this blog so that I have a place to write and catalog some of the many pieces of information that I frequently share on the internet. You see, almost 10 years ago I started riding mountain bikes. I got REAAALLY into mountain bikes, rode most every day. I happened to also be REAAALLLY into vehicle suspensions, and for a lot longer than I was into bikes. Put two passions together and you have my situation today. Over the last bunch of years, I've been fortunate enough to be able to apply some of my suspension ideas to bicycles and most recently motorcycles. They have been pretty well received by riders I think. Along the way I've had the opportunity to apply for some patents to help protect the work I've done, and the bikes that I have designed have won a few World Championships (6) and made a ton of people happy as riders.

Typically I find myself on the fine interweb message boards acting as a tutor, explainer, etc... The fine boards that I frequent are mtbr.com and ridemonkey.com, typically the downhill boards, as that's my favorite riding discipline. Usually I get a question directed to me and put a good amount of typing time into answering the question, but soon the info becomes lost or buried. Typical forum stuff, no big deal. The thing that's tough is that the same question comes back up in three weeks. Sure, I know what you are thinking, save some info somewhere on my cut and paste machine, or maybe become one of those "search feature encouragement Nazi's".

I don't know how I feel about that really. I think that this may be at least as good of a way. We will see.

This blog is the place where I can explain the finer technical points of how the systems I design work, perhaps put some information about new products that are coming out, I don't know, let's see how it goes and take it from there, OK?! I'm looking forward to this.

Thanks for reading!

Dave