sábado, enero 21, 2012
Cervelo P5/ magura brakes for cervelo
cervelo P5 con rotor en fuerteventura
cervelo P5 con rotor en fuerteventura
Cervelo P5: First Ride JIM GOURLEY
It’s daybreak on the southeast coast of Fuertaventura. I curl my toes into the black sand of the beach, and it gives way as softly and warmly as a cuddled puppy. Looking out across the water, I spend several moments scanning the horizon to determine if I really do perceive the curvature of the earth along it, or if the vast expanse is just trying to subtly convince me of the idea. After a bit, I decide that either way it doesn’t matter and settle my mind to just enjoy the view. The earliest bolts of light coming over the barren, wind-swept mountains cast a silver sheen over the ocean. For its part, the sea is placid in its approach to the shoreline. It’s as if the island is so peaceful as not to attract the tide’s attention. Even the pair of seagulls sweeping back and forth along the shore beat their wings in silent contrast to their counterparts in more populous locations. I take a deep breath, and in doing so it occurs to me that you don’t so much breathe in Fuertaventura as you allow the profound serenity of the place to inspire the air into your lungs.
While the meditative aspect is the most refreshing, Cervelo had thousands of other reasons to choose this sleepy island off the coast of Africa to debut their latest creation. As far as training areas go, Fuertaventura is perhaps better suited to time trialists than a meat locker is to Rocky Balboa. Though the entire island is covered with sharp peaks, you can ride all day without meeting a single climb. The island is sparsely populated, the air dry and the landscape barren and windswept. It’s no surprise then that the largest population isn’t native this time of year, but rather professional cycling teams, triathletes and vacationing endurance enthusiasts. For the past two days, the press junket has been touring the island on an assortment of Cervelo’s road bikes. Today is the coup de grace. After the previous day’s two-hour presentation on its design and development, it’s time to ride the P5.
I need a sedative environment to keep me from chomping at the bit. There’s plenty of reason to be excited about the P5. Perhaps more than any other bike they’ve crafted to date, this one is a genuine expression of the Cervelo philosophy. It is fast by virtue of the engineering brainpower poured into its conception, but what makes it truly brilliant is its simplicity and accessibility. Despite qualifying as a superbike with its integrated stem and head tube, the P5 avoids the pitfalls of maintenance headaches by approaching the concept with creative solutions. Instead of integrating the front brake into the fork, Cervelo created a shroud for a bolt-on brake that keeps everything within easy reach. Meanwhile, the rear section just above the bottom bracket was made into the perfect hiding spot for a DI:2 system battery. On top of that, Cervelo ensured that their headset is not only the most aerodynamic on the market, but it is also UCI legal and provides easier cable routing. All of this is bred from an unwavering resolve to make this a machine that provides hours of joy on the road and only a few moments of work in the hotel room or your garage. In terms of superbikes, it’s billed as every rider's dream come true. That’s all on paper and Powerpoint, though. The proof is on the pavement, and I’m eager to answer the penultimate question—“but how does it ride?”
Joining the first series of journalists to try it out, I hop on Frederik Van Lierde’s triathlon-specific model, complete with the front brake cover, triathlon fork, and a disc wheel. Added to the location, the DI:2 shifting and a set of O.Symmetric chain rings make this an especially exotic experience. I wonder if this is how John Smith felt when he first laid eyes on Pocahontas.
Our jaunt begins on a route into a stiff headwind. I remain on the horns for a bit to get settled into the rhythm of the elliptical rings and fully anticipate a sluggish start, but the bike defies expectations and slides right along. I’m shifting gears rapidly just to keep from spinning out, and not with any real effort. This bike wants to go. It surprises again when our course tacks left and I feel the resistance die away and a stiff kick come from the side. Despite the 81mm front wheel and a full disc in the rear, it’s hard to tell if the wind is blowing harder on the bike or myself. After a few extra moments to allow myself to believe the bike is actually remaining stable against such a hard push, I get back into the aerobars and let it rip. Given the extra surface area presented by the P5’s deeper cross section on the seat and head tubes and fork, it’s impressively true to the rider’s guidance. The guides from Cervelo are disappointed at the unusually high wind speed on this day, fearing they won’t allow us to truly get a feel for the bike’s capability. But if anything, nothing lends itself to credibility like crosswind performance, and the P5 aces that impromptu challenge with flying colors. Turning toward home and finally riding with the wind, our group tops 40mph before spinning out in the big ring. Thankfully, Van Lierde is not here to watch as a group of pencil-pushers throws his steed to the ragged edge with greater exuberance than good judgment. At any rate, the bike provides as much excitement in its unbridled power as it does security in its handling. The only tragedy is that the P5 is now carrying us home at warp speed, and I’ve decided I never want to get off it. Alas, bridesmaids and journalists have something in common when it comes to perennial misfortune.
So long as the rubber side stays down, there’s never such a thing as a bad day on a bike. And in this place, on this bike, it’s as close to a perfect day as you can get. Given their history of accomplishment, one says that Cervelo has outdone itself at the risk of being accused of hyperbole. But the P5 warrants such praise. Fast, responsive, stable, and comfortable. It is a truly splendid machine, and our ride was on a beautiful day in a pristine place. There’s no such thing as a bad day on a bike, and whether you’re on a P5 or riding in Fuertaventura, there’s no possible way your day could go wrong.
Cervélo Unveils The P5
By Aaron Hersh
Published Jan 18, 2012
Updated 1 day ago
The frame is UCI-legal. Cervélo offers a triathlon-specific fork that is not. The frame conforms to the regulations stating that tubes must be no more than three times deeper than their width, but Cervélo used a loophole to stretch the seat tube beyond the typical interpretation of the rule. Cervélo senior advanced R&D engineer Damon Rinard says the UCI allows “gussets” that support and connect the frame tubes as long as they are no deeper than the original tube dimension. The P5’s seat tube is 27mm wide, which means it must be 81mm or shorter in the longest direction, and the seat tube is almost exactly that length. The gusset connecting the seat tube and the top tube, however, is another 81mm. These connected elements create a surface that is 162mm at its longest point. A second gusset is used to connect the seat stays to the seat tube that extends the segment of the tube deeper than the UCI’s 3:1 ratio lower on the seat tube. At its widest point, the P5 actually has a 6:1 ratio, yet it still abides by the UCI’s 3:1 rule. Go figure.
Cervélo contends that building a bike with a single tube shape doesn’t make sense. The rider’s body and wheel influence the air flowing around the bike in different ways at different sections of the bike, so Cervélo broke the bike into discrete segments to design shapes optimized for each condition. As a result, the P5 has different tube shapes from the aerobar to the back of the frame. They’re sticking with a teardrop-shaped airfoil instead of a truncated airfoil design for the downtube and aerobar, but some portions including the seat tube have a chopped, flat tail.
The same P5 frame is used for both the triathlon versions and road time trial versions of the bike. As a result, Cervélo did not use outrageously deep profiles for the downtube or head tube such as those on the Quintana Roo Illicito and Specialized Shiv. The triathlon fork, however, is extremely deep. The fork blades and the extension off the front of the bike both create airfoil shapes much deeper than the road version. We tested both bikes in very windy conditions and noticed a slightly greater influence from the wind on the triathlon version.
Cervélo elected to stick with horizontal dropouts, which make wheel removal and reinsertion more difficult than vertical dropouts. These dropouts also allow the gap between the seat tube and the tire to be finely adjusted. Rinard says a gap of 2-6mm is aerodynamically ideal and there is no performance difference within that range, taking into account the rotational aerodynamic resistance against the wheel in its direction of motion created when the air moving with the tire collides with the frame. Hexagonal head screws are sunken into the dropouts. They can be backed out to space the wheel away from the frame to widen the gap or accommodate a 25c tire. The bike is optimized for 23mm tires and when the screws are all the way in the bike, tires of this width fit precisely with the frame. The 27mm-wide seat tube is another change Cervélo made from the P4 to the P5 because of the trend to wider wheels and tires. The P4’s seat tube is 25mm wide, a shape that is optimal for narrower tires, but the P5’s is 27mm at its widest point. The broader tube helps smooth airflow from the frame to the tire and should also improve lateral stiffness.
Aerobar And Aerobar Fit
The 3T Aduro aerobar, a completely new bar with an integrated 9cm stem, comes stock on the P5. It attaches to the bike using a standard 1 1/8-inch steerer tube. An advantage of this traditional system is that the rider can opt to use any other bar.
The Aduro can be set up in three stack height configurations. Cervélo calls them X-Lo, Low and High V. Combined they create 11.5cm of total stack adjustment for each of the six frame sizes with the aero-shaped spacers that can be used to elevate the bars. These spacers are available in 5mm and 10mm heights. All three configurations use the same basebar.
In the X-Lo position, the bar is flipped upside down. This limits the pad fore-aft position to one fixed spot, eliminating all pad reach adjustment.
The low position keeps the basebar in its upright orientation and the pads can be set to three different fore-aft positions. The total reach range is 50mm from the forward-most setting to the furthest rearward.
The High-V setup has the same reach adjustment as the Low setting. It uses a carbon V-shaped spacer to elevate the bars 5cm farther above the basebar.
The brake grip position is identical for all three configurations and cannot be adjusted. The basebar’s straight brake grips are 40cm wide, center to center. The grips do not tip upward, so riders who are accustomed to upturned brake grips might feel initially unsecure on the grips. With a few rides, that perception goes away. The High V spacer used to elevate the pads to their tallest extreme doesn’t elevate the basebar, creating a more extreme drop from the aero position to the braking position.
Cervélo’s front-end system with the Aduro aerobar offers an enormous range of stack adjustment, but arm pad reach adjustment is limited to the three pad positions on the aerobar. This will be a limitation that may force some riders to switch aerobars to fit the P5. Despite the restricted range of adjustment, we found the pads to be supremely comfortable if they fit the rider’s position. They are long enough to minimize pressure on the arm and angled perfectly to guide the forearm to the extensions.
S-bend aerobar extensions are stock equipment with the P5, and these extensions limit reach adjustment of the handgrip position. The Aduro uses a collet system to clamp the extensions. They plug into a mini extension from the basebar and a piece twists downward to attach the basebar and extension. The S-bend’s curve runs into the collet at a reach distance of 32cm from the rear of the pads in the forward-most position to the tip of the extensions. Swapping the S-bends for ski-tip bars or flat bars will increase fit range by allowing the extensions to come back much farther toward the rider.
Accessory And Storage Integration
The only completely integrated storage container on the P5 is a small box hidden in the seat tube in the rear wheel cutout. Originally designed for a Di2 battery, it can also hold flat repair or other any other small items if the bike is built with a cable drivetrain. In addition to this box, the aerobar has threads to mount a standard bottle cage positioned between the arms. Cervélo has maintained for years that a bottle placed horizontally between the arms is the most aerodynamic location, so they decided to make this bottle position a standard feature. The bottle mount is perfectly solid—it doesn’t rattle in the slightest. The bottle is extremely easy to reach. We loved this simple yet effective feature. The down tube also has a mount for a bottle cage, and that’s the extent of the storage options provided by Cervélo.
Although other top-shelf bikes offer more storage or integrated hydration, Cervélo decided to leave the creation of accessories to the hydration companies. The company built solid mounts into the frame to help blend the frame and accessories. They gave X-Lab, TorHans, Dark Speed Works and others an early look at the bike’s unusually positioned bolt mounts so these specialized companies could design products for the P5. Two mounting bolts behind the head tube, one additional bolt beneath the down tube mounts and a seat post mount create a wide range of opportunities for integrated hydration. Dark Speed Works has produced a bento box-style storage container called the Speedpack 480D that mounts behind the stem that is currently available. Some other accessories are already on the way, but they aren’t ready yet. The bike will receive an incomplete grade in this category until those parts have come to market.
The P5 feels exceptionally stiff under foot yet rides smoothly. It’s noticeably stiffer than its predecessors. Cervélo’s patented bottom bracket technology, a taller head tube, integrated stem and basebar design and selectively wider tubes makes the P5’s ride feel noticeably better than the P4. We were pleasantly surprised with its ability to kick over short hills. Handling is difficult to judge after a single ride, but our initial impression was that the bike is very responsive and not a slow carver. The P5 combines Cervélo’s aerodynamic credibility with an outstanding ride experience on the road.
The very first P5s will arrive in early March. These things are so scarce the journalists at Cervélo’s launch event rode Caroline Steffen’s and Frederik Van Lierde’s bikes. The complete P5 Tri (the name for the version with the triathlon fork) with Dura-Ace Di2 goes for $10,000. The frameset is $6,500. The road version is $6,000 with mechanical Dura-Ace and $4,500 as a frameset.
Cervélo will be releasing the build kits and pricing along with the geometry charts. We will have them posted as soon as possible.
Magura RT 8TT: A Quantum Leap In Tri Braking Performance
By Aaron Hersh
Published 4 hours ago
The Magura RT 8TT hydraulic rim brake. Photo: Aaron Hersh
The brake caliper mounts to any standard brake mount. Photo: Aaron Hersh
The lever has a flat grip point and a clever quick release to allow the wheels to be switched quickly and easily. Photo: Aaron Hersh
The brake mounts to any standard basebar. Photo: Aaron Hersh
Two screws easily accessible on the front of the lever screw in to force the pin backward, which slides the middle piece against the second and lifts the curved piece until it presses against the inside of the bar. Photo: Aaron Hersh
The front of the brake has a gap. Photo: Aaron Hersh
The brakes mount with a single brake bolt. Photo: Aaron Hersh
The brakes don't come with brake pads or shoes. Any standard shoe can mount to the brake arms. Photo: Aaron Hersh
They will be exclusive to Cervelo dealers until June and the will first come stock on other bikes in 2013. Photo: Aaron Hersh
Like all hydraulic brakes, the lever, line and calipers are a single unit. The line can be trimmed. Photo: Aaron Hersh
The brake uses standard Magura connection pieces. Photo: Aaron Hersh
Cervélo teamed up with Magura to create a hydraulic rim brake specifically for the P5, and the brakes are also compatible with any tri bike.
Scroll through the photos at the top left of the page for more on the Magura RT 8TT.
The hydraulic stopping system designed by Magura, a premier MTB brake manufacturer, is compatible with all road wheels. The lever mounts to any standard triathlon basebar and the caliper can be installed on any standard fork or frame brake mount.
Although standard brake cables and housing both feel solid in-hand, the pressure applied through the cable and housing stretches the brake cable and compresses the housing, resulting in a mushy feeling and greater lever travel under hard braking. As the cable slides within the housing it creates friction that further hampers brake performance, a problem that has become more common thanks to the proliferation of hidden and integrated brakes. Anyone who has ridden a triathlon bike with extremely tight or circuitous brake cable routing is all too aware that a brake with twisted housing lacks stopping power and lags before reopening after braking. Once a few drops of sports drink leak into the housing, braking performance become even worse. Hydraulic brakes solve all of those problems. Although bikes with straight and simplistic brake routing certainly reduce the problems with cable-actuated brakes, a single ride aboard a mountain bike with hydraulic disc brakes makes the potential of hydraulic brakes immediately obvious, even though these are rim brakes, not disc.
The Cervélo P4’s rear brake, one of the first truly integrated calipers, suffers from those issues and the Canadian company wanted a better solution for the P5. Rather than starting from scratch to design a hydraulic brake themselves, they approached Magura and suggested the two companies work together to create a hydraulic brake for the P5. Magura handled the hydraulic mechanism and Cervélo integrated the brake into the bike.
Cable braking systems use pulling force to squeeze the rim but hydraulic systems only push, they can’t pull. Hydraulic systems functions like this: A plunger is pushed into the hydraulic line running through the basebar when the rider squeezes the brake lever and forces fluid (the RT 8TT uses mineral oil) through the line. This fluid doesn’t compress and a twisted line doesn’t impair its movement, so the hydraulic line transmits all the pressure to the far end of the system, which actuates the brake. This fundamental change from pulling to pushing forced Magura to design a unique road caliper that functions with a hydraulic system. The Magura RT 8TT brake caliper has a piston that sits beneath two brake arms that actuate about pivot points above the piston. The piston drives upward and forces the upper segment of the arms outward to the sides, which rotates the brake arms and forces the lower portion to squeeze inward toward the rim.
Magura claims the RT 8TT can create 44% more force than the nearest competitor listed in their presentation. On the road, it feels substantially more powerful and responsive than a cable-actuated brake. Perhaps the biggest difference in braking feel is the way stopping power ramps up with only a small increase in the pressure on the lever. Instead of putting a death grip on the brake lever to max out the brake caliper’s stopping force, the RT 8TT requires only a subtly tighter squeeze on the lever. Although it would certainly be easier to flip ass-over-teakettle with these brakes than with cable brakes, stopping power isn’t excessive or jerky. With just a little experience, we were able to quickly adjust our internal gauge for the pressure needed to slow the bike. These brakes are not, however, as powerful as hydraulic disc brakes on mountain bikes and they have a little more give when squeezing the rim as well. Although they don’t offer the same stopping performance of a hydraulic disc brake, they are strong and offer a supremely consistent, reliable connection with the brake caliper. They are a fantastic improvement over any other hidden or integrated brake. Don’t be surprised if every high-end triathlon bike comes with hydraulic calipers within a few years.
Magura RT 8TT: A Quantum Leap In Tri Braking Performance
By Aaron Hersh
Published 6 hours ago
In addition to its stopping performance, the RT 8TT is remarkably easy to install and use. The calipers attach to any standard brake mount with a standard brake bolt. The width can be adjusted to fit rim between 17mm and 28mm wide by turning an easily accessible bolt with a 2.5mm hexagonal wrench. This range of rim widths is wide enough to cover every wheel we are aware of. Magura doesn’t yet produce brake shoes (the part that holds the pad) or pads, but the brake arms take any standard brake shoe. A set of Shimano or SRAM brake shoes will mount to the RT 8TT and brake pad angle can be adjusted to match any wheel.
In addition to the width adjustment, the brakes have a quick release switch for easy wheel removal. Should the rider forget to reengage the brakes before jumping on the bike, the brake will automatically reengage itself.
Magura says their complete braking system—calipers, levers, and the connection between the two—weighs 495 grams and “one of the lightest” cable systems weighs 519 grams. They explain that a meter of housing and cable weighs roughly 70 grams, but an equal length of their hydraulic line and fluid weighs only 50 grams.
Shimano Dura-Ace Di2 riders will have to sacrifice their brake-mounted shifters or splice an additional shifter into their system to retain the ability to shift while riding with hands on the basebar. Other than price, the inability to use these Di2 shifters is about the only drawback we can find to these brakes.
Magura doesn’t yet produce a splitter that would allow for a third brake lever that could be installed on the aerobar extensions.
The brakes are only available with aero brake levers for now, but Magura product manager Stefan Pahl says, with a smirk on his face, that they will offer road-compatible versions “not too far in the future.” Magura will also release a cheaper version called the RT 6TT that is functionally identical to the RT 8TT but heavier.
The brake lines must be bled periodically to remove any air that makes its way into the line, but these brakes should require less service than cable brakes. They must be centered using the brake bolt only. There is no fine lateral adjustment of the pads.
The RT 8TT will come exclusively on the Cervélo P5 until April 1. On that day, Cervélo dealers will receive components for aftermarket sale at the kingly price of $750 a set, without pads or brake shoes. Dealers that do not carry Cervélo will have access in June and other bike companies will be able to spec the brakes as part of their complete builds in 2013.