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As seen in RTR Issue #21 - Spring 2006

Review #127 Calfee Tetra CF Tandem | Carbon Fiber Technology Gives the World a Wonder

by Bill Wheeler

Calfee Tetra CF Tandem

A long time ago, virtually every bicycle was made from steel tubing. Then a few pioneering bicycle builders began to develop aluminum tubes as an alternative to steel. Once aluminum frames were refined, steel and aluminum had almost an equal share of the bike market. These days, though, it seems like carbon fiber is beginning to take center stage as the favorite material. On many group rides now, carbon fiber-framed bikes will outnumber the steel and aluminum bikes, and even the older bikes are commonly upgraded with new components made of carbon fiber. Carbon fiber can be used to create bikes that are lighter in weight as well as stronger than traditional metal parts. An added benefit of carbon fiber is that it can make our bikes more comfortable to ride due to the way carbon fiber frames and components absorb or dampen out vibration and bumps. As with most cycling technology, carbon fiber originally was used on single-rider bikes, but is now being used to make tandems.

One of the most experienced manufacturers of carbon fiber bikes is Calfee Design. Craig Calfee has been building carbon fiber frames for nearly twenty years. His bikes have earned a reputation as some of the best in the world. After perfecting his skills building single carbon fiber bikes, it was only natural that Calfee would progress to building tandem frames out of the material. The results have been very impressive, and Calfee Designs now includes several tandems in its product line. Several stock sizes are available for buyers who can fit them. Calfee can also custom-build bikes and tailor the frames to match the riders’ weights, physiques and desired ride qualities. My wife, Evie, and I recently got to spend over a month test riding the latest model of the Calfee Tetra tandem. This was our first opportunity to ride a bike of any kind with a carbon fiber frameset, and the experience has been quite enjoyable and eye- opening. Now we understand why so many of our friends who own carbon fiber-framed single bikes love them so much!

The test bike came in the “nude” finish that clearly shows the grayish-black color and patterns of the carbon fiber in the tubes. The lugless tube junctions were similar in color, though they looked as though someone had taken rolls of black tape and wrapped multiple layers around each junction to hold the tubes together. It gave a somewhat bulky look to the frame, though not to the point of making it look excessively clunky. Running a finger over the tube joints revealed a seamlessly smooth surface, with no hint that the frame wasn’t simply made in a mold in a single piece. The dull color and look of the bike belied its high-tech, high-performance capabilities. It made me think of the old hot-rodder’s term “sleeper,” which refers to a car that looks very plain and unassuming on the outside, but which has a huge engine under the hood that can blow the doors off a competitor’s car in a drag race. For customers who don’t care for the plain grayish-black look, Calfee offers a nice selection of colors that can be applied to the frames in everything from subtle fades all the way to solid colors. The graphics on the frame were comprised of several white “Calfee” or “Calfee Design” logos accompanied by their trademark chambered nautilus shell symbol in a yellow color.

One of the most striking features of the Tetra we tested was its lack of a lateral tube. Most Calfee tandems do use the standard design that includes a lateral tube, but Calfee now also makes tandems without them. The test bike looked rather strange and open without a lateral tube running from the head tube back to the stoker’s bottom bracket. The lateral-less frame design has the double benefit of reducing both the weight and cost of the frame. Since there are several fewer tubing junctions to have to fabricate on the lateral- less frames, it significantly reduces the labor and materials needed to manufacture the frame. It’s one of those rare cases of less being more. In fact, the cost of the lateral-less Tetra tandem frameset is about $1400 less than the standard Tetra frame!

We have heard comments from some people that a carbon fiber-framed tandem would be excessively flexy, and we wondered if the lack of a lateral tube would exacerbate any potential frame flex. The rather large diameter of most of the Tetra’s frame tubes--2 1/8-inches for the down and bottom tubes, and 1 7/8-inches for the top tube--did give the bike a rather strong, beefy appearance. The seat tubes had more svelte diameters of 1 5/16-inches, while the seatstays and chainstays were 9/16-inches and 13/16-inches in diameter respectively. The rear dropouts were made from machined metal that was molded into the ends of the chainstays while being attached with screws to small metal fittings in the ends of the seatstays. The left rear dropout included mounting holes for a disc brake, though the test bike came equipped with a set of Ultegra dual-pivot road bike brakes. The test bike’s rear width was 140mm, but Calfee can build bikes with many other widths to accommodate whatever hub widths the customer desires.

The bike had mounts for four water bottles: One on the downtube, a pair on the front and back sides of the captain’s seat tube and one on the stoker’s seat tube. The bottle cage mounts actually consisted of studs that were attached to the frame tubes, and the cages were then mounted using self-locking nuts. I’ve seen a photo of a Calfee tandem with two bottle cages mounted on the underside of the stoker’s top tube, so Calfee buyers can apparently order their bikes with as many bottle cage mounts as they need and in various locations on the frame.

Completing the frame was an Alpha Q carbon fiber fork. The straight-bladed fork has blades that are just over 2-inches from front-to-back just below the crown, and which taper down to a ?-inch round tip at the dropouts. The fork has a 1 1/8-inch diameter carbon fiber steering tube that was installed in the head tube with a Cane Creek S-8 threadless headset. The dimensions of the frame included a 55cm (21.5-inches) long captain’s top tube, a 56cm (22-inches) captain’s seat tube (center-to-top), a stoker’s top tube 67cm (26.3- inches) long and a stoker’s seat tube of 47cm (18.5-inches). With both seatposts nearly all the way down in the seat tubes, we had a nice fit for both the 5’10” tall captain and the 5’2” tall stoker. When straddling the frame, I was just touching the top tube, which had a standover height of 77.5cm (30.5-inches).

After examining the frame, the next most-noticeable feature of the test bike had to be the wheels. Calfee equipped this bike with a set of Topolino wheels. This particular wheelset is a set of Topolino C19 wheels that Calfee modified with a longer rear axle to fit the 140mm width of the rear dropouts. These rather expensive wheels are technological marvels in their own right. The hubs are made of a thermoplastic carbon fiber composite. The bearings are sealed units that turn extremely smoothly and with no noticeable drag. The lightweight aluminum rims are connected to the hubs with “Carbon Core”carbon fiber-Kevlar spokes that are blade-shaped to cut through the air. Topolino’s website says these spokes weigh only 40% as much as a standard straight gauge steel spoke, while having three times the tensile strength of steel spokes.

Something that is unique about these wheels is that the spokes aren’t actually connected to the hubs. Instead, the spokes simply pass through passages in the hubs and connect to the spoke nipples on opposite sides of the wheel. The are no elbows or other highly- stressed points of attachment to the hub. The ends of each spoke have a short, threaded metal tip embedded in a small plastic sleeve, and the threaded tips connect to standard spoke nipples protruding through the rims. Additionally, down near the hubs where the adjacent spokes cross each other, the spokes pass through small plastic guides that keep the spokes from rubbing against each other. The little plastic pieces detract a tiny bit from the looks of the wheel, but they don’t add any appreciable weight or rotating mass. The front wheel has 24 spokes.

The rear wheel has 30 spokes, with 18 on the drive side of the hub and 12 on the non-drive side. This arrangement helps balance out the asymmetrical wheel dish.

The result of all of these lightweight, high-tech parts is a wheelset that is very strong yet weighs in at just under 1400grams for the pair. Calfee can build their bikes with dropout spacing as wide as 160mm, so symmetrical wheels such as those used on Santana’s tandems could also be used on the Calfee. The folks at Topolino have been working with Calfee and may soon be producing some of their outstanding wheels with axle spacings to fit tandems. Only long-term testing would reveal how well the wheels would hold up under the stresses of tandem use. The wheels we got to try out on the test bike were very nice, and I’d like to see Topolino go into production with tandem-specific wheels. The comfort factor alone would make them a nice upgrade, as the wheels did absorb a lot of the road shock and vibration.

Getting the riders’ power to the rear wheel was handled by a Shimano Ultegra tandem triple crankset turning a set of 30-42-53 chainrings that connected via a pair of SRAM PC-991chains to a 9-speed SRAM PG-990 Powerglide II cassette with 34-28-24-21-18-16-14-12-11 cogs. This gearing combination proved adequate for all of the riding we did, though our middle-aged bodies were breathing pretty deeply on some of the steeper climbs we rode up. Shifting duties were handled by a set of Ultegra STI levers connected to an Ultegra front derailleur and a Deore XT long-cage rear derailleur. This drivetrain performed flawlessly during our entire test period, and we had no missed shifts or dropped chains.

One interesting feature of the Tetra was the cable routing. The derailleur cable housings go from the STI levers into holes in the lower front sides of the head tube. From there, the derailleur cables pass along the underside of the down tube and through grooves cut in the bottom surfaces of the bottom bracket shells. The rear brake cable housing similarly fits into a hole in the upper left side of the head tube, and then the cable runs along the left side of the top tubes, passing through guide holes drilled though the sides of both seat/head tube junctions. The brake cable had several of those tiny rubber “donuts” installed along its length to prevent the cable from slapping or chafing on the side of the top tube.

In addition to the carbon fiber frame and spokes, there were several other carbon fiber components on the bike that helped to achieve both an amazingly low weight as well as a very comfortable ride. These included the handlebars and stoker’s seatpost. The handlebars were especially nice in that they had a flattened shape between the stem and the top outer bend to the STI levers. This flat section provided a much larger contact area for the palms of the hands and helped to spread out the pressure points and greatly reduce the problems of numbness and impact forces. The inboard sections of the bars, besides having grooves molded into the undersides to provide channels in which to route brake and/or shifter cable housings, also had ergonomic indentations on both the front and rear edges to provide a natural place to grip the bars during climbs.

The captain’s bars were mounted to the bike via a Ritchey aluminum stem. Once a captain gets his or her stem extension and rise angle dialed in, they can have Calfee fabricate a one-piece handlebar & stem to install on the bike in place of the standard stem. Calfee calls this a BarStem, and they can fabricate them using almost any brand and model of carbon fiber handlebars on the market. The benefit of using a one piece stem & bar unit is that it adds another section of carbon fiber--the stem--to isolate the captain from road shocks and vibration.

The stoker’s compartment on the test bike featured a BarStem mounted to a metal clamp to attach it to the captain’s seatpost. This BarStem added to the stoker’s comfort, as did the stoker’s Easton carbon fiber seatpost. The captain’s seatpost was an aluminum American Classic post. Topping off the seatposts was a pair of Selle Italia SLK saddles.

I’m sure you are wondering by now just how much this bike weighed. The overall weight of the bike, including our Shimano 747 dual-sided mountain bike pedals and three water cages, came to an incredibly-low total of 28.5 pounds. This is less than the weight of many single bikes! One of the little side benefits of this featherweight bike is that it’s very easy to move around when getting it into and out of the house. Instead of each of us having to lift an opposite end of the bike to maneuver it through the tight turn through our front door without scuffing the walls or door, either one of us could easily pick up the Calfee and carry it in or out. We didn’t transport the bike in or on our car, but I’m sure that tandem owners with roof racks would appreciate the ease with which they could lift this bike onto or off of their car’s roof rack.

After we got over our amazement at the Calfee‘s minimal weight, we were eager to get out and ride it. We logged about 350 miles on the bike, and it met or exceeded our expectations in every way. The first thing we noted about the bike was how its low weight translated into faster acceleration and higher cruising speeds than we are accustomed to. When taking off from a stop, the bike was very easy to accelerate up to speed.

The lightweight Topolino wheels no doubt contributed to the bike‘s snappy performance. It was easy to do quick sprints on this bike, a feature we made use of several times while riding in traffic and having to make fast lane changes and other maneuvers. It made riding in heavy traffic almost fun. We were consistently able to cruise along on the Calfee two or three miles per hour faster than on our own tandems. To be fair, though, our personal tandems all have rear racks and rack packs mounted on them, and the tools and other stuff we usually lug around in those packs do add weight and drag to the bikes. On the Calfee, we carried just a minimal amount of tools and accessories in a small fanny pack, so that also helped us to ride faster than normal. Cruising on the Calfee was fun, and we expended noticeably less energy to maintain our speed than we were used to. Soon after noting how light and fast the Calfee was, we discovered the next best thing about the bike: It is incredibly comfortable. The combination of the carbon fiber frame and fork, carbon fiber-spoked wheels and carbon fiber handlebars and stoker stem results in a bike that soaks up all but the biggest bumps and bangs.

It was amazing to ride along some of our regular ride routes and feel almost like we were floating along above the road surface. Only the really big impacts made their way up to our butts and hands, and even those bumps were greatly dampened out by the time they made it to our bodies. Younger riders might not appreciate this characteristic as much as we middle-aged riders do.

Most of us “baby boomers” who have been riding for much of our lives have put our bodies through lots of pounding over the years on bikes that transmitted most of the road shock and vibrations right into our hands, butts and feet. Now that we are older, many of us are more interested in having bikes that are comfortable to ride than in having the fastest or flashiest bike in the group. Carbon fiber allows bikes to be built that can actually be lighter and faster than many steel or aluminum bikes, while simultaneously providing a big increase in comfort for the riders.

I think that as more and more middle-aged cyclists get ready for active retirement, a large number of them are going to buy bikes with carbon fiber frames and other components as their chosen rides. The ride quality of the Calfee was quite impressive. We were able to arrive home after riding 40 or 50 miles with little or none of the soreness we often feel after riding a medium-length ride on a metal- framed tandem.

The benefits of carbon fiber were especially noticeable with our hands. What small amount of the bumps and road vibrations that did transmit up through the bike were further dampened out by the carbon handlebars, and the flattened-out inner sections of the bars spread the forces out across a larger area of our palms. There was only one ride during which I felt any numbness or pressure points in the palms of my hands, and even that was far less than I often experience with the aluminum handlebars on our personal bikes.

The comfort was similar for both the captain and stoker. Evie felt the Easton carbon fiber seatpost seemed to give her as much comfort and shock absorption as a suspension seat post.. The only things we found to be uncomfortable on the Calfee were the Selle Italia SLK saddles. About ten miles into our first test ride, Evie commented that the saddle was not at all comfortable for her. I reached the same conclusion for myself about 25 miles into our second test ride. We replaced the SLK saddles with a pair of saddles from one of our personal tandems for the rest of our test rides. Saddles are a very subjective item, though, so we can’t really fault the SLK‘s. I’m sure there are lots of riders out there who find the SLK saddles comfortable for them.

Riding the Calfee was a blast. The Calfee’s steering is somewhat quicker than that of our steel and aluminum Santana Sovereigns. It took me a few rides on the Calfee to get used to the quicker handling to where I could steer a straight line rather than doing a little squiggle every time I’d reach down for a water bottle or Evie moved around in the back. Once I got used to this faster steering, it was no problem.

The handling of a bike is another one of those personal, subjective preferences. For riders who prefer a bike that handles a bit on the fast side, the Calfee would probably be perfect for them. For other riders, who might be doing long rides or multi-day tours, perhaps with a loaded-down bike, the somewhat more stable steering of a Santana might be preferable. Evie and I both felt the comfort factor alone would make the Calfee a nice bike to use on a century ride, despite the bike‘s quick steering. We both thought a 100-mile ride on the Calfee would leave the riders much less beat up and sore at the finish line than most other tandems would.

Throughout our riding, the Calfee performed flawlessly. The Shimano STI levers mated to Shimano derailleurs shifted flawlessly. The SRAM chains shifted smoothly across the Ultegra chainrings and SRAM cogs. The gearing on the bike was useable over the entire range of riding, be it fast cruising on level ground, climbing or descending. Likewise, the Continental 700x25C tires performed very well. They gave excellent traction and a comfortable ride throughout the test period. We only rode in dry conditions, so I can’t report on their handling on wet pavement. We did not experience any flats in the hundreds of miles we rode. I did miss having a Flite Deck computer on this bike and being able to easily tell what gear I was in without having to glance back and try to see the chainrings and cogs. I felt that mounting a computer magnet on one of the carbon fiber spokes might cut into the spoke and cause damage or failure. While checking out the Topolino website, though, I discovered that Topolino has a special computer magnet available which has a wider slot and is made especially to fit their wheels’ spokes without causing damage. Another thing that impressed me a lot about the Calfee was its extremely quiet ride. The bike cruised along virtually silently, even over most rough pavement, adding to the feeling that the bike was almost just floating along above the asphalt. The Tetra’s lack of a lateral tube made me expect the bike would be flexy during climbs, but this turned out not to be the case. We did a fair amount of climbing on the bike and, surprisingly, we didn’t notice any significant flex in the frame. Even when both of us were standing and pedaling hard up a steep climb, the frame felt stiff and the bike tracked straight.

On those standing climbs, though, the wheels did make a strange shushing sound as we pedaled hard and rocked the frame slightly back and forth. The noise reminded me of that disconcerting noise that wheels sometimes make on their first use after a rebuild or truing as the spokes and nipples start to get seated in. It was hard to tell if the spokes were flexing at all during those standing climbs, but we could not detect any loosening of the spokes while we had the bike. When we stayed seated during climbs, though, the wheels did not make any unusual noises. On climbs, the Calfee’s low weight and the low rotating weight of the wheels made climbing noticeably easier. What goes up must come down, of course. We did a fair number of fast descents on the Calfee. The bike was quick to accelerate up to speed on a downhill, and it carried its speed well into the next uphill. On straight descents, we got the bike up to about 45mph. On twisty descents I cautiously kept the speed down to about 35mph or less, as I felt somewhat nervous after the wheels had made that odd noise during our standing climbs. Overall, though, the Topolino wheels were great, and I think they contributed a lot to the Calfee’s fast acceleration and comfortable ride. If Topolino does eventually produce a tandem-specific wheelset similar to the wheels we rode, I wonder if they will add a few more spokes to the wheels or make any other changes to beef them up to handle the extra weight and forces a tandem puts on wheels?

The ability to stop quickly and safely is just as important as the ability to go fast. During our rides, the Ultegra dual-pivot brakes front and rear performed very well. Stops were fast, smooth, and controllable. I didn’t get a chance to test the brakes to see of they’d fade or overheat the rims when used on long, steep descents. If this was our personal bike, though, I’d prefer to have a disc or drum brake on the back instead of having to rely on just rim brakes. It should be noted that the thermoplastic carbon fiber hub shell of the Topolino rear wheel does not have provisions for mounting a drum or disc brake. For tandem teams who don’t do a lot of riding in the mountains, the regular rim brakes would provide more than enough stopping power for the bike.

There were only a few very minor things I could find to complain about on the Calfee, and these were rather nitpicky. First, since the derailleur cable housings fit into recesses in the sides of the head tube, you can’t use those little screw-in cable adjusters that most other bikes have installed in the cable stop on the downtube.

The front derailleur doesn’t have a built-in adjuster barrel the way the rear derailleur does, so the test bike came with an inline adjuster barrel installed on the cable housing between the STI housing and the head tube. The housing for the rear derailleur did not have an inline adjuster though. I think it would be a useful thing to have an inline adjuster barrel up front on the rear derailleur cable’s housing, too, to allow the captain to make any needed adjustments of the rear derailleur “on the fly,” rather having to stop and get off the bike to turn the adjuster on the rear derailleur.

My next comment concerns the rather bulky junction of the captain’s seat tube and the top tube. I have rather large thighs. Since I had to have my seatpost lowered almost all the way down to achieve the correct leg extension, this placed my thighs close to the tube junction. There were many times when I could feel the insides of my thighs lightly brushing against the sides of the tube junction with each pedal stroke. It wasn’t enough to cause any actual chafing, but the slight brushing was a little annoying at times. The Calfee tandems with lateral tubes may have slightly narrower top tubes and junctions that don’t need to be as wide and beefy as those on the lateral-less frames, but captains or stokers with big thighs might want to choose a small frame size to allow the seat tubes to position the riders a little higher above the tubing junctions.

Another minor comment is about a similar problem with the large top tube and those little rubber “donuts” on the rear brake cable along the left side of the top tube. There were several times when the Lycra of my shorts or tights would momentarily make contact with one of the little donuts and cause a slight “snagging” feeling as my leg moved past the top tube. Again, this is probably a result of the unusually-large diameter of the top tube reducing the clearance between the bike and the riders’ thighs. Riders with slimmer thighs than mine might not have any problem with their clothing contacting the rubber donuts.

I think that in the years ahead, tandems with carbon fiber frames such as the Calfee Tetra, Santana Beyond and others will become the bikes of choice for a significant number of tandem teams, especially baby boomers who are getting up into middle age or beyond.

Our experience with the Calfee showed us that bikes like this can do almost everything well. They are lightweight, fast, fun to ride and, perhaps most importantly, extremely comfortable. They can be used for everything from racing, fast training rides, touring, centuries, or an easy Sunday morning breakfast run. The low weight does compensate, at least a little bit, for the decrease in strength and endurance that most cyclists go through as they get older, and the amazing comfort provided by carbon fiber helps make longer rides a fun experience rather than something to be endured.

After having the opportunity to ride the Calfee on a regular basis, it will be hard to transition back to riding our steel and aluminum tandems. Evie and I have already decided that our next tandem will definitely have a carbon fiber frame. I think it can honestly be said that once you’ve tried carbon fiber, you may never want to go back to your old bike again. The only real drawback about carbon fiber tandems right now is their stratospheric price tags. Let’s hope that as hundreds of tandem teams start buying carbon fiber tandems, the prices will come down at least a little bit so more riders can benefit from the incredible ride and low weight that bikes like the Calfee Tetra tandem have to offer.

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