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P4 Ride Review
By Jon Wojcik, Mario Bonano, and Kim Ross with contributions from Tom Demerly and Ron Tew.
Read this first about our reviews

2009 Cervelo P4 Ride Review

Ford Motor Company Proving Ground, March 5th, 2009. Jon Wojcik evaluates the new Cervelo P4.

Cervelo’s P4 debuts at dealers this month with the initial production run of 56cm bikes and frames shipping now, additional sizes follow soon.

No other bike has been as widely anticipated. A combination of factors ranging from use of internet forums to the growth in triathlons along with success of previous models from Cervelo means there is more buzz about the P4 than any bike in history. Those are big shoes to fill.

2009 Cervelo P4 Ride Review

The P4 is poised to establish itself as the aerodynamic reference with numerous, subtle (and not so subtle) aerodynamic enhancements.

Most of the hype surrounding P4 has been speculation in a gulf of real information about the bike. As of early March 2009 almost no one has ridden one. Nearly no one has raced on one.

As the P4 begins arriving in Cervelo dealers around the world it begins a trip toward earned credibility. People have bought them. They will race them. The clock will tell the tale. Cervelo has set the bar very high with their previous models. The P4 is poised to clear it.

Cervelo set an internal standard for improvement on the P4 that was difficult to attain. Doing so meant some unusual approaches to conventional and seemingly banal challenges. The design philosophy was one of integration and attention to detail. It takes into account not just an aerodynamic frame, but a functioning aerodynamic bicycle that integrates a drink carrier to subvert certain UCI technical restrictions and reduces drag of key components.

2009 Cervelo P4 Ride Review

Viewed from the front the cross section is oddly narrow, "Like riding a razor blade" said Wojcik.

Starting at the front of the P4 the first thing you notice is how narrow the bike is. Oddly narrow. It remains narrow for the length of the bicycle. The downtube is 27 millimeters wide at its narrowest and bulges to 45.5 millimeters wide beneath the deeper frame section near the conformal water bottle.

The fork on the P4 is a proprietary design for Cervelo. There were 75 different fork and frame designs considered before the current one was deemed optimal. It is a deceptively complex design.

One detail few people have noticed is the front wheel recess in the down tube. The down tube of the P4 has a subtle, barely detectable front wheel indentation to reduce the proximity of the front wheel/tire to the down tube and reduce drag. This is not a cut out, as front wheel cut outs actually have a detrimental affect on bicycle aerodynamics that is not detectable in the wind tunnel. In a wind tunnel a bicycle’s front wheel remains perfectly still with no steering input. The fork is rigidly held in a fixture even when the front wheel is rotating. On the road, in the real world, as a rider controls the bike by steering it down the road there are constant, subtle movements of the front wheel relative to the down tube. Cervelo’s close down tube proximity to the front wheel combined with an optimal leading edge design are tested to be low drag not only in a wind tunnel, but for real world conditions where the bike must be steered on the road to ride straight. Cervelo invented the front wheel cut out design in 1995 but never used it on a production bike since they subsequently learned from prototypes that it offered no tangible benefit in the real world.

2009 Cervelo P4 Ride Review

It is hard to see, but look at the subtle curvature of the down tube under the "4" in P4: The downtube is recessed for minimal turbulence between rotating wheel and downtube. This is a real-world design that takes into account micro-steering while riding straight.

At its closest point to the front wheel the P4’s down tube is 75.5 millimeters deep. As the downtube continues toward the bottom bracket it becomes 81 millimeters deep. Subtle dimensional changes like this are what provide the P4 with its elusive low speed aerodynamics, and they appear over the entire length of the bike. The bike looks simple but the more you examine it the more subtly complex it becomes.

The head tube is hourglass shaped. As you view the bike from the front the main triangle is entirely shielded from view (and airflow) behind the head tube. There are very minor increases in width- all within the width of the head tube- to facilitate the attachment of the seat stays. The narrowest point in the main triangle of the frame appears on the seat tube between the seat stays and bottom bracket: It is only 23.5 millimeters wide- the width of a road tire. This narrow section improves both aerodynamics and ride comfort.

There are access ports on the side of the down tube on P4. These mark the point at which the cable housing stops inside the frame and the cables continue to the front and rear derailleurs. These are only used during assembly and major cable overhauls.

Front and rear derailleur cables and rear brake cables dive inside the frame just behind the head tube. If your builder does a nice job of sizing your cables they should be invisible from the front of the bike- and to the wind.

2009 Cervelo P4 Ride Review

Proprietary fork integration and cable entry points as well as the cable access panel are visible here.

The top tube is perfectly horizontal, parallel to the boundary layer of air moving around the bike. This low drag design makes a mockery of every aerodynamic bike with a sloping top tube. Sloping top tubes simply aren’t as aerodynamic since they increase frontal area. You don’t need a wind tunnel to intuit this. A horizontal top tube is the lowest drag configuration.

The rear brake is gone from the exterior of the P4. It isn’t tucked outside the chainstays; it is simply gone- integrated inside the chainstays and covered by an aircraft style access panel with two aerodynamic locking points. The wind sees nothing except a couple millimeters of exposed brake pad. The brake itself is an elegant scissor assembly that has incredible stopping power (we locked up the rear wheel easily) but is 1/3 lighter than a standard Shimano Dura-Ace caliper brake. This brake is an engineering coup.

The seatstays on the P4 are as ponderous as a Möbius strip. The union with the seat tube is parallel to the air flow. It’s a remarkable shape, and an elegant piece of design sculpted by the wind tunnel. The tail cone below the seat stays performs a difficult dual role of maintaining an orderly reassembly of flow coming off the frame to prevent vortices along with the mysterious management of air swirling around the tire- perhaps even back in the opposite direction of travel of the bike. The relationship of air flow back here is complex and Cervelo spent an enormous amount of time researching the optimal shape for this area alone.

2009 Cervelo P4 Ride Review

The heavily faired seat tube has a non-perpendicular leading edge and contoured trailing edge. Not the horizontal attachment of the seat stays: An aerodynamic coup.

Chainstays on the P4 are a complex shape that is designed to manage flow between the rear wheel as it rotates and the rear end of the bike. There is a bulge on the drive side to stabilize the turbulent flow caused by a rider pedaling.

The previous generation of “bulge” disk wheels won’t fit between these flat, aerodynamic chain stays- we test fit both the HED Jet C2 and the Zipp Sub 9. Neither will fit. The P4 isn’t alone here- Ridley’s Dean and Noah, The Scott Plasma, The Giant Trinity Alliance and the Argon 18 E-114 won’t accommodate a bulge rim disk either.

 

2009 Cervelo P4 Ride Review

This is a flat Zipp disk with clearances shown. There is generous room and excellent brake performance with a flat disk.

2009 Cervelo P4 Ride Review

Race wheel clearance is a concern. We tested HED Jet "bulge" disk, Zipp Sub 9 and standard Zipp disks. The rear end design of the P4 effectively reduces or eliminates the necessity for a "bulge" design disk by effectively managing drag of the bike relative to the rear wheel at the chainstays.

 

The bulge rim disk is a wheel design concession to facilitate older, less aerodynamic frame designs. In others words- bulge disks are meant for bikes with poor rear end aerodynamics. The bulge disk wheel is an attempt to “solve” or improve previous aerodynamically poor chainstay designs. The P4 doesn’t need a bulge disk. The aerodynamics are optimized on the bike not by wheel choice. The benefit is that you don’t need a bulge disk to optimize aerodynamics- you can use an 80 millimeter deep rim, a flat disk, a standard lenticular disk or any more conventional rear wheel. The chainstays on the bike fix the issue of aerodynamics between wheel and frame. The wheel doesn’t have to make up for a less sophisticated bike design. The aerodynamics are built into the frame- not the wheel.

The P4 gets Cervelo’s new adjustable horizontal dropouts with adjuster screws. There is a nice, new knob for easy adjustment of the dropout screws- you don’t need a screwdriver anymore.

2009 Cervelo P4 Ride Review

Wojcik settles in: "It’s different from anything I’ve ridden. It’s solid, but there isn’t much there."

P4’s color scheme (or lack of one) has received mostly criticism. To their credit, Cervelo is predominantly an engineering firm, not a design studio. They are a culture of pragmatists. P4 is essentially a blank canvas. Somewhat oddly, the bike does not say “Cervelo” anywhere on it. The company marque only appears once on each side of the fork, but no where on the frame. While it would have been easy to hire some graphic designers to conjure up a colorful paint scheme that really isn’t the point of the P4. The bike isn’t for everyone; it isn’t intended to be an ornament. It is a tool, and a refined one. It is Spartan and utilitarian. I can say with certainty that in as little as five years we will look back on this very bike, and this very paint scheme, with reverence. It arrives as a classic by virtue of the lore surrounding it. Even without a paint scheme or any race results it is already one of the most sensational bicycles ever sold. It is impossible for the P4 to be understated, but its paint livery at least pays lip service. Personally, I’ve already set aside a prized collection of decals to make mine look oh-so-racy. It’s the ten year old boy in every man. Remember that wooden race car you made in Cub Scouts?

Jon Wojcik, a veteran, elite level triathlete who competed nationally during 2008, was our test rider for the 56cm P4 you see in our photos. As Jon walked across the black asphalt, helmet in hand, to clip into the P4 for the first real test ride I couldn’t help but conjure images from the movie “The Right Stuff”. This was like a test flight in the X-15, complete with chase planes. Wojcik clipped in, turned the thin black bike nose-on to our camera vehicle and, at top speed over the blacktop road, appeared to be levitating. The bike is so narrow it simply disappears.

2009 Cervelo P4 Ride Review

Brake pads peek out from under the chainstays.

2009 Cervelo P4 Ride Review

The conformal bottle system in place.

Wojcik is a triathlon bike connoisseur, owning a concours de elegance of tri bikes including the Trek TTX, Cervelo P3, Look 586, Felt DA and other flagship triathlon bikes prior to clipping in to the P4. His exposure to the ultra high end tri bikes, his competitive resume and his 6’0” stature made him de facto test pilot for this first production run of P4’s. Wojik put the P4 through its paces on a cold spring afternoon near Ford Motor Company’s Dearborn Proving Ground.

“There is less underneath you. It feels lighter. It is different than the P3”, said Wojcik. He likened ride quality as a function of the slippery aerodynamics, making the bike “disappear”.

“It’s a weird feeling. It’s different from anything I’ve ridden. It’s solid, but there isn’t much there. Like riding a razor blade.”

Could he feel the difference in frame aerodynamics? “I think so…”

We can’t tell if the P4 is faster. Yet. Race results will bare that out. With no independent wind tunnel test capability we can’t say if it is faster, or how much faster it may be if it is. To Cervelo’s credit, their general ethos of design has been to let the wind tunnel dictate the design of the bike. This has mandated a “form follows function” approach to the P4 and produced its unusual configuration.

We believe it is likely faster. Having ridden it but not raced it, we simply do not know yet. Our sense is that the tale will be told on Monday mornings around the country when people log on to see their race results after a Sunday triathlon. Those mornings and the bikes splits people see may be the P4’s single greatest endorsement.

Until the clock stops on the first P4 bike splits we’re not certain if it is tangibly faster. I’m not taking any chances though. Mine will be here soon.

 

© Tom Demerly, Bikesport Inc.
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