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P4.
By Tom Demerly.

2009 Cervelo P4
The new 2009 Cervelo P4.

The air was as thin and dry as a paper cut. There was a deep roar in the room. The lighting was poor. Through a bulletproof window a shape stood insignificant to the blasting column of air that surrounded it.

The P4 prototype.

We couldn’t talk about it, couldn’t photograph it, couldn’t sketch it. We signed a document to that affect and were reminded repeatedly of the fact. In a room littered with images of supersonic planes and inert smart bombs Phil White of Cervelo gave us the presentation. Of course, we were not allowed to tell anyone. We moved up to the wind tunnel and there it was. Technicians watched monitors with barely dancing numbers. Small streams of smoke slipped over it without a flutter. At first glance the wind seemed to pass through it, not around it.

2009 Cervelo P4 2009 Cervelo P4
Cervelo's Phil White and Tom Fowler begin a presentation on the design history of the Cervelo P4 at the San Diego Low Speed Wind Tunnel.

No other bicycle in history has been as widely anticipated as the Cervelo P4, the bike that is intended to raise the industry standard of aerodynamic bicycles. For the months prior to its September 24th unveiling at the Interbike Bicycle Trade Show in Las Vegas internet posters combed Google for spy images, a photo of an athlete on a prototype, an accidental release of a wind tunnel test. When mention of the bike was made in the subject line of internet forum posts thousands of views accumulated within hours. In the bike world it was more widely anticipated than a new I-Phone.

2009 Cervelo P4 2009 Cervelo P4
Security badges and non-disclosures were required to view the invitation only presentation in San Diego. Weapons and aerospace testing was done in this same facility. A cluster bomb sits unattended during the presentation.

The security that surrounded the P4 was impressive. Cervelo was so concerned about the details of the bike being revealed that they built an entire photo studio inside their own facility and called a photographer in for their own web shots. They did not tell the photographer what he was shooting. “We weren’t going to risk taking it to another location just for photos” Said Cervelo’s Brett Kane.

There were no leaks, no spy photos until September 22nd when, at 2:23 A.M. Pacific Standard Time the “Varese Photo” surfaced on the Slowtwitch forum. The Varese Photo, posted by an anonymous user called “roadbiker” showed a nondescript black bicycle with a few odd details but little else worthy of comment. The Varese Photo was actually discovered by an Austrian named Bernhard. Bernhard said he could not take credit for the photo, but that he found it on the website of an Austrian photo agency. Bernhard did confess that it was “too much honor” to be the first person to reveal the Cervelo P4 to the thousands of multisport enthusiasts and Cervelophiles who clambered for months for just a glimpse.

2009 Cervelo P4
2009 Cervelo P4
The "Varese Photo" shot in Varese Italy at the Cycling World Championships accidentally revealed the P4 hours before it was officially unveiled. The photographer is unknown.

What the Varese Photo revealed was the enigmatic P4, captured 18 hours earlier at a race in Italy. The bike was not to be officially revealed until the following day at Interbike, but the difference in time zones created roughly 24 hours of confusion over when the bike should have been shown in public. "They should not have taken it outside" Said Cervelo's Phil White. An anonymous photographer was in the right place at the right time, not unlike the infamous Zabruder/Kennedy assassination film, and the internet forum mavens picked the photo to pieces. Within hours the Varese Photo had been viewed nearly 30,000 times. Forum users had enlarged and enhanced it, trying to decipher every detail about the bike’s new design. No one knew for certain if they were looking at a P4. But they were. The bike had been camouflaged without its distinctive hydration conformal palette in place and no “P4” graphic.

Anticipation surrounding the P4 is well founded. The Cervelo P4 follows Cervelo’s design philosophy of change only when warranted by improvement. When Cervelo began to think beyond the industry leading P3C they set an internal standard that the design would not be finalized until they had appreciated a 20% reduction (improvement) in aerodynamics. It took three years. The result is a bike said to be 20% more aerodynamic than the bike already more aerodynamic than any bike in the industry according to Cervelo- and to other authorities in bicycle aerodynamics.

The implications are significant. For the rank-and-file age grouper it is a $4800 (frameset price) ticket to a faster bike split. More significantly, to the industry, the P4 makes everything else second best by a tangible margin, forcing other aero bike makers back on the defensive. With an approximate 20% improvement in frame aerodynamics the P4 could save a decent age group athlete an entire minute or more during an Olympic distance triathlon and over six minutes at an Ironman distance race. Considering the top three in local age group triathlons are frequently separated by seconds the P4 enables athletes to literally “buy” places. Example: Had I ridden a Cervelo P4 in the 2008 triathlon season instead of my current P3C it is probable I would have won my age category three more times than I did- the time savings in my age category would have moved me up between one and five places in nearly every event. For the age grouper on the bubble of qualifying for Clearwater or Kona the P4 may be the edge that gets them to the big luau.

2009 Cervelo P4
The evolutionary lineage of the P4 from developmental prototype
and into previous models such as the P3C, P3 and P2.

Controversy surrounds the Cervelo P4 similar to that of the Speedo LZR swimsuits used at the Beijing Olympics. Olympic teams who did not have the new Speedo suits were at a disadvantage. Athletes using the suits, including Michael Phelps, swept the medals. Controversy raged over whether the suits were “fair” and how much they actually helped. The same rings true for the P4. Is a bike that is 20% more aerodynamic than the next fastest bike “fair”? Certainly not. How much will it really benefit the rider? Difficult to tell conclusively, but athletes who want to do their best won’t take chances on not having the fastest equipment. Just like the Olympic suits, as more P4’s make it to top age groupers the playing field will be re-leveled at a place higher than it is now. Until then the early adopters of the P4 will enjoy a technological edge that puts them minutes farther up the road.

The things that make the Cervelo P4 faster are an amalgam of subtle refinements. Each refinement serves a purpose validated in the wind tunnel. Some refinements are conspicuous, such as the novel enclosed rear brake, most are more subtle. The end result is verifiably lower drag numbers than any other aerodynamic bike according to Cervelo’s wind tunnel tests. It is worth mentioning that Cervelo is the only company publishing wind tunnel data in their dealer manuals along with other brands and models shown by name as a benchmark. Cervelo calls the other bike companies out on aerodynamics, and no one is answering since they can`t approach these drag numbers.

2009 Cervelo P4

A. Top tube cable routing for lower frontal area.
B. Refined head tube section.
C. Integrated fork/downtube shaping with lowered downtube.
D. Access port for cable routing.
E. Enclosed rear brake assembly (hidden inside chainstay).
F. Low pressure aero profile chainstay.
G. Rear derailleur internal cable exit point.
H. Newly redesigned dropout adjusters.
I. Lowered aerodynamic seat stay mounting.
J. Completely concealed seatpost binder bolt.
K. Refined smaller cross section seat tube.
L. Conformal water bottle/Bento Box aerodynamic system integration.


2009 Cervelo P4
Ultra-narrow hourglass shaped head tube.

Beginning at the front the P4 has an incredibly narrow cross section. These theme of maintaining a very narrow overall forward shape is a critical aerodynamic tenant. The narrower it is, the faster it goes. The P4 is extremely narrow over its entire length with frame shapes that harkens back to the days of the Hooker time trial bikes, the Lotus bike and the Project `96 Superbike from GT. There is also the hourglass suggestion of the head tube and the subtle forward bulge that recalls the front of a P3 but is shaped slightly differently.

The aero head tube is further improved over the P3 with a different silhouette and transition from head tube to down tube and top tube. Bob Duncan of Wheelie Fun Multisport made the observation that only about five centimeters of the top tube is the same as the P3. The rest of the shapes are completely new.

Internal cable routing moves from the sides of the downtube to the top of the bike further reducing drag and frontal area. A removable access port enables mechanics to route the cables through the frame more easily. The rear derailleur cable is fully enclosed to the chainstay.

The new fork on the Cervelo P4 is proprietary to P4 and the subject of more testing over greater time than any other part of the bike. This is likely the most aerodynamic front end ever built on a production bike. Cervelo claims it is and offers supporting data to prove it. Air moves over a bicycle at very low pressure as a result of the (relatively) low speeds bikes travel at. For this reason design cues from automotive and aerospace don’t translate to lower bike speed. This is the reason for the subtleties of the P4’s shape, especially the integration of the fork and head tube/downtube area.

2009 Cervelo P4
Cervelo's unique, proprietary fork is specific to the P4 and melds smoothly into the head tube. Note the close proximity of front wheel to down tube for optimal aerodynamics, outperforming front wheel cutouts.

Cervelo pioneered front wheel cutouts going back to their original Barrachi aero prototype but subsequently learned the front wheel cutout is not as effective as thought at reducing drag. As a result of these findings the P4 has no front wheel cutout. Instead the entire downtube has been dropped very close to the front wheel. The resultant gap between the front tire and the leading edge of the downtube is noticeably smaller compared to other bikes- even ones with cutouts. It is another elegant solution to a complex problem. Other companies have come up with such novel approaches as locating the entire bottom bracket shell off center in a more convoluted attempt to achieve a similar affect.

2009 Cervelo P4
Overall ultra-smooth shape minimizes parasite drag caused by exposed bolts.

2009 Cervelo P4
Completely sterile binder bolt area.

The new seat post binder area has been sterilized of parasite drag. There are no exposed bolts, no protrusions whatsoever. It is as though the seatpost simply appears out of the P4 frame. The binder bolt is a vertical wedge configuration that is actually easier to use than the two bolt style on the P3 and P2. The seatpost itself remains unchanged from the P3.

2009 Cervelo P4
Complex, elegant melding of seat stays to seat tube. Note how the union is actually parallel to the flow of air around the bike. This was a very difficult part of the P4 to design and manufacture.

Seatstays on the P4 are a complete redesign and elegantly complex. They mount low on the seat tube union, out of the air flow and with minimal frontal area. The amazing part about the seatstay attachment point is the connection with the frame is oriented horizontally, parallel to the boundary layer of air moving around the bike. To do this the carbon fiber must do a "Mobius" type curve at the top of each seat stay. Of course there is no brake here, so the aerodynamics are a significant leap forward above other bikes, not just because it is missing from the traditional location, but because it is nearly missing entirely. Many bikes have adopted the design theme of moving the brake near the bottom bracket. This doesn`t make the brake more aero, it just makes it less visible providing an impression of streamlining without any aerodynamic benefit. The rear brake on the Cervelo P4 is actually concealed inside the frame, not just sitting on top of or under the bottom bracket.

2009 Cervelo P4
The horizontally bulging low pressure aerodynamic chain stays as viewed from the rear.

Most photographers have missed the radical re-shaping of the chainstays. The stays bulge enormously in the horizontal plane. They fill in the space between the rear wheel and the stays and flare outward away from the bike as well. While this initially appears to be a concession to either ride comfort or stiffness or both, Brett Kane of Cervelo explained the shape is entirely aerodynamic in design. The P4 was shown with flat Zipp 900 series disk wheels. Brett Kane of Cervelo mentioned that “Lenticular disks do fit” in the P4 but said he did not know if Zipp’s Sub 9 would fit. Judging by the proximity of the stays to a 900 series flat disk I wager the Sub 9 won’t work on a P4 because of its increased width and greater flex at the rim.

At the bottom bracket/down tube union the P4 features a conformal water bottle/spares case carrier. This carbon fiber "bottle cage" is melded precisely into the frame shape. It can be removed and replaced by a conventional bottle cage. The space is occupied by either a 570 ml (20 ounce) water bottle that is fillable on the fly from a standard bottle (as handed up in a race aid station). The space will also accommodate a "Bento Box" carrier which will house a spare tire, CO2 inflator or even the battery for Shimano's novel electro-mechanical shifting suite.

2009 Cervelo P4 2009 Cervelo P4
Conformal hydration/Bento Box carrying system. Note: Bottle shown in photo is prototype, not production. Note 2: Mounting system bolted to frame with standard bottle cage bolt.

While the water bottle integration has raised eyebrows it is testimony to how truly difficult Cervelo's self-assigned goal of a 20% reduction over the P3C was to achieve. It simply couldn't be done with just the bike. This degree of drag reduction required sideways thinking that includes building the water bottle into the bike. The bike is much more aerodynamic with the bottle on board than without. One could argue that the Cervelo P4 is indeed a frame build around a water bottle. One would have a tough time arguing this design is anything less than highly effective in reducing drag. The bike will be sold with two bottles included and supply of bottles won't be a problem since Cervelo had to order an enormous quantity to amortize the tooling costs.

2009 Cervelo P4
Conformal system improves overall bike aerodynamics. One size bottle fits into all frame sizes. Bottles readily available from Cervelo. Two bottles are supplied with frame.

While the most noteworthy aspects of the P4 are meticulous attention to aerodynamic detail there are sweeping mechanical updates. The rear dropouts and rear dropout screws are entirely reworked. The new dropout screws include a finger-adjustable turnwheel in a small hollow space behind the dropout. Not only is the new dropout design more robust, it is much easier to adjust. A flush cable routing port on the right side of the down tube near the head tube enables the mechanic to easily route the internal cables through the downtube toward the bottom bracket. The brake cover under the chainstays uses a turn key lock that is actually airfoil shaped and parallel to the airstream when locked. The combination of the brake mounting and reduction in hardware compared to a conventional rear brake result in a 30% weight savings compared to standard Shimano Dura-Ace rear caliper. Instead of equalizing the torque between two binder bolts as with the P2C and P3C the P4 uses a single bolt.

2009 Cervelo P4 2009 Cervelo P4
Refined dropout adjusters with hand adjustable turn wheel.

The P4 is a difficult bike to make due to the complex shapes, intricate tooling and specific lay up of its carbon fibers. Early production will be slow and limited. P4's are allocated to Cervelo dealers based on a "P4 to other bike" ratio system. The more other Cervelos the dealer buys, the more P4's are allocated to them. Smaller dealers will not have access to the P4. With quantities limited and lead times stretching well into 2009 the bikes will sell out complete well before the first one arrives in stores. Popular Cervelo dealer Austin Tri Cyclist sold through an 11 bike allocation the day after the bike was announced. Within hours of the bike's introduction Bikesport had sold two. For anyone aspiring to a P4 in the 2009 season December '08 will be too late.

2009 Cervelo P4
New seat tube profile.

Sizing on the Cervelo P4 runs consistent with the Cervelo geometry story and adopts the previous Cervelo P3C fit coordinates. The bike is proposed to be sold two ways: A frameset for $4800 USD and a SRAM Red equipped bike for $6800 USD with an as-yet unspecified parts ensemble.

2009 Cervelo P4 2009 Cervelo P4
Cervelo's Phil White demonstrates the enclosed aerodynamic rear brake. The brake assembly is 30% lighter than an externally mounted Dura-Ace brake caliper.

The hype and the wait surrounding the introduction of the Cervelo P4 created a level of anticipation that was nearly impossible for any product introduction to live up to. Some consumers were underwhelmed by the P4's stealthy graphics and subtle aerodynamics. The features and benefits of the bike come in above the heads of many consumers and there will be a learning curve associated with the P4 and its capabilities. As the benefits confirm themselves in race results the understanding of how Cervelo achieved a 20% drag savings over the previously fastest bike will develop. As appreciation for this technology spreads it will have a "de-selling" affect on other bikes with contrary design philosophies. The majority of Cervelo P4 buyers in the first two days of the bike's availability have been prior Cervelo owners. They know the benefits and understand the technology- they "drank the Kool-Aid". Having downed more than one cup of Cervelo flavored Kool-Aid myself and appreciating the faster bike splits I ordered the new flavor before it had a name. The Cervelo P4 is not just a great design from a great company, it has become a great story too, and not a single bike has been delivered to dealers yet...

© Tom Demerly, Bikesport Inc.
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