Chris Cocalis Interview

In: Bike Industry News, NEWS By: Karl Rosengarth On: November 12, 2009

chris cocalisChris Cocalis, the man behind Pivot Cycles, recently visited Dirt Rag headquarters. Before we treated Chris to the fine mountain bike trails out our backdoor, we sat down with him and talked about the Mach 5 review bike that we had just received, and about Pivot Cycles in general.

DR: Can you start by talking about the Mach 5 bike design?

CC: The Mach 5 is a 140mm travel bike. Some of the newer 140mm bikes fall more toward a "freeride-light." But the Mach 5 falls more toward our Mach 4 or our 429, or cross-country based bikes. It has all the capabilities, but at the same time has the pedal feel that somebody would feel comfortable doing an endurance event or 24-hour race on this style bike.

The whole idea of the bike is that it’s neutral handling, not overly slow or overly quick. It also climbs really well and doesn’t flop around in the front end. It steers slightly to the quicker end, compared to something like the Blur LT. I use that comparison because it’s a good baseline and a lot of people know how that bike behaves. This is the one bike that really does it all. If you’ve got a bunch of bikes in your garage and you’re not sure if the bunch of guys or girls that you’re going riding with are going to hammer the hell out of you, or take you on super-technical stuff, this bike will do everything.

A few of the things that kind of define what Pivot is: we really focus on frame stiffness. The lower linkage has eight cartridge bearings in it. We were the first people on the mountain bike side of things to develop an oversized, press-in bottom bracket. We actually developed it with Shimano, it’s a 92mm wide BB, the shell diameter is larger than a standard thread-in bottom bracket , and the entire XTR bottom bracket presses in. With the wide BB, the bearings are in the same relative position as they would be in a thread-in external cup, but they’ve got better support all around them with the bigger shell. They’re more protected inside the shell. Because the load of the bearings is sitting right on the frame, instead of hanging out off a threaded section, you don’t get the tendency for threads to pull and creak. It eliminates a lot of set-up problems like: is the bottom shell faced correctly? Is the distance from seat tube to the drive side face absolutely correct, so the chainline is correct? With that 92mm shell we can get our pivots a lot wider, the downtube can be wider, and everything down there can be bigger and stiffer without adding weight.

pivot mach 5

DR: How many different bottom brackets are compatible with the design?

CC. Well, when we first developed this, we did it solely with Shimano. Every frame ships with an XTR bottom bracket in it. Even on this bike with our XT/SLX kit, the bottom bracket is an XTR, which comes with a three-year warranty, so you get a much higher-end bottom bracket than what’s typical. That design is also compatible with FSA and Race Face cranks. They’ll just slide right in there. FSA now makes a press-in bottom bracket with ceramic bearings that’ll go in there. But it’s actually heavier than the Shimano bottom bracket that’s in there.

And we’ve actually been working for the past six months with SRAM on a composite press-in BB, because the Truvativ GXP cranks have the floating bearing—they’ve got two different sized bearings. We’ve got the final pre-production stuff at the office. So Pivots will now be compatible with any Truvativ/SRAM crank. The new SRAM XX group is coming out and we wanted to make sure that, with the 2×10 stuff, particularly on our Mach 4 frames, that we’re compatible with every crankset on the market.

The other thing is, around that bottom bracket area we basically start with two forged halves and weld the bottom bracket shell together. Then the entire unit gets put on a CNC machine and all the tolerances are properly held. The front derailleur mount is machined into the right-side forging, and it’s a direct-mount front derailleur so it uses an E-type style that bolts right on. Again we’ve been working with SRAM and they will this year have a front derailleur for their XX that will bolt right to that same mount.

And between the 92mm bottom bracket shell and the direct-mount derailleur you get a much more precise set-up. Again, there’s no facing needed. That’s one of our key quality control checks on every frame—we measure from the face of that derailleur mount to the outside of the bottom bracket so that we know chainline is perfect on every bike. When we send out a complete bike the front derailleur is mounted and the bottom bracket’s in.

Because the mount is directly on those forgings it’s really the most rigid front derailleur mount on the market. When we first came out with Pivots and were at the first Interbike, we were talking so much about the suspension design and everything, and people would come back and go: "Wow, I’ve never been on a bike that’s shifted like this." It’s instantly noticeable that all those things add up to a very immediate shift, and there’s just no flex in the system.

pivot mach 5

The head tube of the bike—we use a 1 1/8" zero-stack on it. It’s not an integrated. It’s actually 1 1/8" cups that sit level with the head tube. That allowed us to do a couple of different things. The head tube gets much larger. The outside diameter of the head tube is very close to the size of a 1.5" head tube. So it allows us to have bigger tubes coming into the head tube. With the bigger tubing, we get better front-end stiffness. You don’t have to squish the tubes down—overall better frame stiffness.

The zero stack also allows us the ability to take over an inch out of the front end of the bike. In some cases, like a medium or a large frame, it’s not a big deal—we ship a tall headset cap with the bikes. When you’re talking about some of the other sizes we do, we have an extra-small frame that is like the lowest stand-over 5.5” travel bike on the market, with a women-specific geometry. And that lower front end goes a long way to achieving that stand-over. If you’ve got somebody who likes a longer top tube and wants to get into a racier position, that applies a lot more to the Mach 4. And it’s a really big thing on the 429—keeping that front end down.

And you know on longer-travel bikes, a 5” to 5.5” travel bike used to come with a 125mm fork and then they were 130mm and now they’re 140. And we’ve got a lot of customers buying frames and putting the new 150mm Fox on there. A few years ago when the new standards came out, they increased the minimum clearance between the tire and the arch, so all those things keep creeping up the length of the fork. Kind of going back to that versatility of using the bike for everything, all the way to endurance racing and sport-level racing, and keeps that front end height in check.

pivot mach 5

DR: How would you boil down the overall functioning of the rear suspension in layman’s terms?

CC: It’s a dw-link bike, and a dw-link is a version of a dual link bike where there is an upper and a lower linkage. The benefit of any dual link bike, compared to a single pivot, is that you can move that single pivot around anywhere and you can change the wheel travel path, but it’s always going to be an arc. Same thing whether it’s an ABP or a Horst link bike. With a Horst link you have the option to move two pivot points around, the one at the bottom bracket and the one below the dropout. And you can change that wheel arc, but it’s always going to be an arc. Chain forces and certain things affect that arc at certain points in the travel, and you have to find a balance of how you set the travel path to be the best for maybe sprinting at the beginning, might not feel as good through the middle, you might have to control more things with damping.

With a dual link bike we have the ability to change that path, so it doesn’t have to be one constant arc. I’ll compare to Santa Cruz because they pioneered the idea of, and their whole marketing thing was based on, that S wheel travel path, and that’s completely different from what we’re doing. A dual link allows you have something that goes in an S or a V, other than an arc. So we can take a look at what you want when you’re pedaling under power versus how the bike feels through the middle of the travel.

And my background is in 4-bar Horst link bikes and there’s a couple things they do very well, and one of those is that they are fully active under braking. When you put the brake on, the suspension continues to work. That’s one of the traits with our dw-link bike, even compared to some of the other dw-link bikes—we designed it to have basically no effect on the braking, a fully active suspension design. In fact if I lay the braking torque curve over some of the bikes I’ve done in the past with a Horst link, it’s identical. So you can carry more speed into rocky, bumpy corners and the suspension doesn’t stiffen up in the back end, and it just works better through the bumps.

But one of the things that the Horst link bikes didn’t do as well—the pivot down below the dropout—as the suspension starts to move through its travel, the wheel starts to rotate forward very quickly in the beginning parts of the travel, and when you hit square-edged bumps it’s almost like you’re ramming. Two things are colliding with each other. With this and the ability to do different travel paths, we actually have a more rearward wheel travel path in the first part of the travel. That does a couple things. You get much better square-edged bump performance. It rolls through the smaller trail junk a lot easier. It also is part of what goes into the pedaling performance of the bike, you get better traction on climbs, better squirt out of the corners, the bike just sprints really well. In the middle of the travel it’s very similar, in our case, to a four-bar link bike: active, smooth, very vertical wheel travel path.

pivot mach 5

The other thing too, with no pivots on the back end, we can really triangulate the rear triangle and have a much stiffer back-end. Between the short lower link, its proximity to the upper link, and the general size for them and the bearings that are in there, the rear triangle is just incredibly stout and stiff. So all your power is getting to the rear wheel.

One of the patents that covers the dw-link is called the anti-squat patent, and it’s unique within the suspension world because it’s the first idea where—pretty much all suspension bikes, when a designer’s working on them, you’re taking into account wheel travel path, the chain torque on the full suspension, how the braking affects the suspension bike—Dave Weagle’s anti-squat patent basically covers the rider’s center of mass, and how it sits in relation to the suspension. And when you bear down or shift your body weight to pedal, that is really the most dominant force on the bike. And typically heavier compression damping controls that bobbing that’s created, or that loss of energy from the rider’s body weight shifts. Stuff like Brain shocks, lockouts, whatever—to keep the suspension from bobbing around.

The whole idea when I’m working on designs with Dave is that for a given size bike, I’ll give him a range of rider saddle heights that would fit a specific sized bicycle, what stem length we’re going to spec and even which riser bar, and he’ll calculate a center of mass. So I’ll have all the things I want to achieve as far as wheel travel path, suspension rates, but then he’ll do all the anti-squat calculations on where we need to finally move those pivots so that rider mass shift doesn’t load the suspension up.

pivot mach 5

DR: So those pivots—are they proportionally scaled for different sized frames?

CC: The lower links are generally in the same spot, but the upper link placement and the angle of it, on the Mach 5 on the small and the extra-small, are in a completely different place than the medium and large bike. The rear triangle is different. Everything is different on that. On the small and extra-small we’ve gone to a different stroke shock but we’re getting the same amount of travel out of it.

The other thing is that the frame stiffness makes a huge difference. Everything that we do is really designed for frame stiffness so that all the power gets down. I think that there’s a lot of suspension bikes on the market where the suspension might be inherently good, but the frames are so flexy or have such a bad pivot problem that it masks things and makes the suspension seem poor, because there’s other things going on.

Our eight cartridge bearing main pivot—that’s not a six-month service or replacement deal. From some of the stuff I’ve done with previous designs, we expect customers will get five to seven years out of these main pivot bearings. The pivots are big, the way it tightens down doesn’t side-load the bearings. Those bearings are called Enduro Max bearings. They’re designed specifically for pivots. When you pull the seal off of them instead of having a bearing cage inside the cartridge bearing, the cage is not in there, and there’s actually and additional bearing. The load capacity of each bearing goes up considerably. The tendency for a bearing to notch out as it goes through its cycles is greatly reduced because the bearings are stacked up against one another, instead of an eight or sixteenth between them because of the cage in between them. They’re some of the highest quality bearings in the world.

Almost every part on that frame is cold forged. The lower yoke that goes to the rear triangle is a cold forged part. Then we CNC machine the entire back and insides out of it, and basically make a shell out of it, and then weld plates on the bottom so you get this very lightweight but incredibly strong box-section part with no openings in it. In the area where the entire frame stiffness relies on, we’ve beefed things up without adding weight. Carbon fiber upper linkage: it’s strong, light, it looks really cool. Between the frame’s stiffness and the pedaling performance, we want somebody to go faster, more efficiently on the bike.

DR: Can you talk about the 2010 shock and how that plays into the design?

CC: I talked about the anti-squat, and we actually call it "position sensitive anti-squat" because depending on what gear you’re in and what incline you’re on, your body mass position changes and it really changes the amount of anti-squat resistance. When you’re going downhill and your mass shifts, the anti-squat is much lower that it is when you’re cranking up a climb. So we’ve got a lot of things that we’re really optimizing for the different conditions that you would encounter on the bike.

The Fox shocks previous to this year , when you make a valving change in the shock it affects the entire range . The Boost Valve changes it from damping that affects the entire range to ability to control the last 40 percent of the stroke independently. So for this bike, it really allowed us to open up both the compression and rebound damping and lighten them up tremendously, and still have that control through the back end of the stroke, and even through the tail end of the middle. So you don’t get this wallowy hammock, but the bike has a higher level of plushness in roots and rock gardens.

pivot mach 5

DR: Is that Boost Valve rear shock tuning something you worked on with Fox?

CC: Yeah. Fox has had similar technology in their DHX. They have the ability to package it in the RP23-type shock, and they said, "Is this something you could use?" Actually me, Dave Weagle, Hans from Ibis, and Dave Turner were really pushing on Fox to get us some new things that we thought could advance it. I’m sure they would have eventually done something like that, but they kind of shelved the technology a couple times to wait and see.

So you got the tune we design for Pivot and everything. Last year’s bike was great, but this just takes things to a whole new level, and kind of follows that philosophy of what we’re trying to do, of getting the bike optimized for every type of riding and every situation that you can encounter.

DR: How do they separate that out?

CC: The Boost Valve is actually a separate valve system that gets pressurized. Like on the DHX Air 5.0, you put a shock pump on the reservoir, and the range on that one is anywhere between 150 and 200-something psi. I think the shock has a sticker on it that says what the Boost Valve pressure is. Depending on whatever that separate valve system pressure is set at, it changes that ramp from about 60%-on in the stroke. So, not only were we messing with those pressures, we were also changing the new valve stack and everything.

The shock has the ability to go much lighter on the damping than the previous version shock, so we have the ability on both ends to do things that weren’t possible before. Depending on what pressure they pressurize , that affects how that valve opens and ramps up. So now you’ve got a shock that—the shock previously was mostly speed-sensitive, so depending on how fast you hit a bump and the oils hitting these shims and blowing them open or flexing them—now we have both speed- and position-sensitive valving. The Boost Valve kicks in at a certain point in the travel and can affect that end stroke. How much it affects or how much bottoming control you get is directly affected by how much Boost Valve pressure you put in that shock.

DR: And those vary by bike size?

CC: No, they vary by bike model. So the Mach 5 Boost Valve pressure is different than what we run on a Firebird, different than what we run on a Mach 4 and a Mach 429. Because, as I mentioned, the smaller bikes actually get a different-stroke shock and smaller rear triangle, even though they get the same rear travel. Part of the idea there is that the general valving is tuned for a range of rider weights. So a rider on a medium frame that weighs 180lbs., say they run 160psi in the rear shock. A rider on a small or extra-small frame that weighs 115-120lbs. will run about that same pressure. So the valving and everything works identically, we’re just leveraging that shock a little bit more.

And we really do that to a greater degree on the double-extra-small and extra-small Mach 4 frames, where we get women down to 4’11" who weigh 90lbs. Most bikes that are women-specific, even if they went down to that size, the shock just doesn’t work for riders of that weight. We make sure that everything from size to size handles that rider weight range.

And in general, between the frame stiffness and the shock pressures, we’re a very low leverage-ratio bicycle. So the shock pressures run very low. If you have a big rider, even a 300lb. guy that wants to ride a Pivot, they’re not putting 300-plus psi in the rear shock. I’m 200lbs, and I think I run 155psi in that shock. So, it works for a very wide range of riders. The shocks on some bikes are so leveraged that you get anybody really much over 180lbs. and things start to get compromised pretty heavily. That’s not the case here.

DR: Is that the larger canister on there too? What’s the advantage of going to that versus the standard size?

CC: When we first came out with the Mach 5, we actually had the small can on there and the ramp on it was so much that it felt a whole lot like a Mach 4. You really had to hit something to get the full 5.5” of travel out of the back end. So for the next year, we decided to test more with the big can, and made valving changes that would allow the bike to use the stroke more, but at the same time we made valving changes that wouldn’t cause it to just dip into the middle.

And this Boost Valve shock takes that to the next level. We’re just able to tune that combination and have a smoother stroke and still get the ramp at the end through damping and not have to compromise the mid-stroke on it.

Yeah, the way the bike is leveraged and everything—when I first designed this bike, the rates were very, very close to the Mach 4, and we wanted to basically make the back end plusher. I actually have customers that are doing 24-hour races but they like the comfort of this bike and they’ll either buy a second shock or they’ll buy the second can from us—it just unscrews and goes on there—it really gives the bike a racy, cross-county feel. It doesn’t sit down into its travel as much.

DR: I can see that if you like to race occasionally, you want it to feel more efficient.

CC: You know on the flip side we have riders ordering large cans for their 429s and putting 120mm forks on it—it’s fine. You can put a 150mm fork on this and make it even more trail-bikey and relax the angles even more.

pivot mach 5

DR: Where do you have them made?

CC: That’s a good conversation. We build the frames in Taiwan. But it’s quite a bit different than the typical Taiwanese frame. Actually some of the high-tolerance hardware we make in our facility, like the bolts and the pivot pins, things like that. The weld rod is proprietary weld rod that’s made in the U.S., that we actually box and ship over there. We have three CNC machines in our shop. We basically have a full production facility, and instead of just doing a blueprint and taking it over to a vendor over there and letting them build the whole bike, we actually build all the frame fixtures, all the tooling to hold each step of the process. We’ll do the first pilot production run, we’ll bring their people over, and we’ll show them the weld order and how to build that bike from start to finish. Then we’ll transfer our tooling over to them.

And then when the frames come back, there are 28 steps that we go through, where the rear triangle gets put on its own alignment fixture and checked, the head tube gets re-faced, every item you could possibly check on the frame is double-checked and then we assemble the whole frame ourselves, torque all the bolts, press in the bottom bracket, make sure everything is correct and on the money, so that the perfect bike goes out. The frame manufacturer that we use over there is a very small family-owned frame manufacturer. We have our own weld line and the three guys that weld our frames, they’re like the brother and the cousins of the owner, they’re experts at what they do.

The company had not built suspension bikes before I went over there, so we didn’t go to a place that says, "We build a million suspension bikes a year, we’re going to do it the way we do it." I wanted to show them how we build a suspension bike, and how I build a suspension bike, and basically how I did it at Titus. The controls, the much more aerospace-like process of fixturing and holding and not just tacking and bending shit back into place somewhere down the line. Quite frankly, the typical Taiwan process is: get it through production fast and then we can fix it later.

Even like special heat-treating fixtures that hold the rear triangle pivot point in place. The front triangle—after everything is welded, heat treated and aligned—the entire front triangle gets put on a CNC and the pivot points get bored to the correct locations. There’s just a much higher level of fit and finish.

Really, when it’s all said and done, I could build the frames for the same or possibly less in my own facility doing all the production here, but all the forging capabilities are over there, all the hydroforming capabilities are over there. And then when it comes to the processes like anodizing and laser etch—in the city Taichung, where most of the bike industry lies, there’s a couple heat treaters that literally treat almost everybody’s bicycle and they’re expert at not making a frame warp like a pretzel when it’s heat treated, and how to hold it. Anodization is very difficult on a bicycle frame with all the nooks and crannies, and differences in front and rear triangles. There’s literally nobody in the U.S. that can anodize a frame as well as those guys over there. So our goal is to build the best bike frame in the world and that takes a concerted effort of tooling design and engineering from us, and a lot of the processes that they have that we no longer have in the U.S. So that’s the long answer to the short question of where the bikes are made.

The other thing I want to mention about the bikes—because of anti-squat and that they pedal so well, the bikes are really designed to run 30% of sag into the rear shock. And pretty much every other suspension bike on the market, the tendency is to cheat sag to get them to pedal a little bit better. In fact, when I used to work in bike shops we used to say, "Put a little more air in it, it’ll give good parking lot." On Pivot bikes, if somebody doesn’t run that amount of sag you basically wind up with a bike where the front end loads up, you don’t use the full suspension travel and the experience just isn’t nearly what it could be.

At the same time, you could leave half the air out of that rear shock and pedal around and sprint, and it will still pedal as efficiently. You can play with it and let a little too much air out of the shock and, hey, you know, this thing sits more relaxed but it still pedals exactly the same with less air. It’s just that when you put too much air in it, all of a sudden it doesn’t pedal the same, it doesn’t feel all that great. At that point it feels like an average suspension bike. So that’s an important thing to point out.

As I mentioned, this is our 2010 model with entry-level spec. We have a philosophy where we’re not shooting for specific price points. I have a philosophy that I won’t put anything on a bike that I wouldn’t ride personally. There’s stuff that has tremendous value and works great, and we use that stuff. But I’m not compromising by putting a crappier wheel on the bike just to hit a given price point.

When you look at the wheels, they’re high-end DT Swiss wheels, they all got Super Comp butted spokes, they’re Pro Loc alloy nipples so they don’t back out, and they’re all hand-built wheels. They’re custom-built for us in Grand Junction.

We could shave a lot of money by putting something other than a Shimano crank on there, but that new SLX crank with composite middle chainring is stiffer and it just shifts better than anything else. The SLX rear derailleur is nice but there are a lot of steel parts on it and it weights quite a bit, so we go to XT in that area.

Everything from the nice WTB chromoly saddle… the Kenda dual tread compound Nevegal tire is the top-of-the-line tire. Even on the entry-level bike it’s the same rear shock. When most people are trying to hit a price point, that 15mm axle adds considerable cost to the bike, they’ll just put the 9mm on. But for a Pivot customer, there’s just certain key performance areas, and I want to make sure that those are covered and that they’re getting all the cutting-edge stuff.
 

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