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.
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.
| 
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. |
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. |
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.
| 
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.
|
| 
This is a flat Zipp
disk with clearances shown. There is generous room and
excellent brake performance with a flat disk. |
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.
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.
| 
Brake pads peek out
from under the chainstays. |
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.
