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OVER the next three weeks, nearly 200 professional cyclists will compete
in their sport’s longest and most gruelling race, the annual Tour de France.
They will cover 3420 kilometres in 23 stages, from windswept plains to semi-vertical
mountain passes in the Alps and Pyrenees. The times that riders take to
complete each stage are added together at the end of the competition and
the winner is the cyclist who crosses the finishing line in Paris with the
least accumulated time.

Last year Greg LeMond, an American, won the race in 87 hours 38 minutes
35 seconds. His average speed was 37.14 kilometres per hour, but what is
most startling about his success is that he was just 8 seconds ahead of
the second-placed cyclist, Laurent Fignon, a Frenchman. Never had victory
in the 85-year-old event, the 77th to be held, been so slim.

As cyclists in the Tour de France have become more evenly matched and
squeezed winning margins from minutes to a few seconds, so their teams have
had to look to the design of their bikes to give them the competitive edge.
This puts designers under pressure, because the bicycle is already one of
the most efficient machines.

LeMond’s success was put down to a clip-on extension on the handlebars
of his bike. The extension is little more than a padded U-tube to support
the rider’s elbows. By leaning forward onto the tube, LeMond improved his
aerodynamic shape without compromising his riding position. The first U-tubes
appeared in the mid-1980s, made by Profile, an American company. Subsequent
wind tunnel tests at the Texas A&M University, Austin, showed that cyclists
using them were 90 seconds faster over 40 kilometres than those without
them. In the 1989 Tour, LeMond was 50 seconds behind Fignon at the start
of the last stage of the race, which was 27 kilometres long. The U-tube
helped the American to cycle 58 seconds faster over the distance. Fignon,
the defeated Frenchman, recognised the advantage. He fitted the U-tube to
his bike’s handlebars for a subsequent race in southern France – and won
in record time.

Until about 20 years ago the basic shape of the ordinary bicycle had
changed little since the turn of the century, and that of the racing bicycle
since around 1930. According to Frank Whitt and David Wilson in their book
Bicycling Science, published in 1982 by MIT Press, many studies worldwide
indicate that the amount of energy wasted during the transmission of power
from the legs to the rear wheels is tiny, about 1 per cent of that applied.
Wind resistance causes the biggest energy losses.

More recently, particularly during the past five years, both the design
and manufacture of racing bicycles have changed radically as the machines
in this year’s Tour de France will exemplify. For instance, TVM, the Dutch
team led by Australian cyclist Phil Anderson, will use bicycle frames made
of die-cast magnesium alloy for the first time. According to their designer,
Frank Kirk, the frames, which are 91 per cent magnesium, are as stiff and
as light as the best conventional frames but much cheaper to produce.

Ever since people started to race bicycles, frame builders have had
to compromise over the qualities of lightness, rigidity and strength. A
light frame, for instance, has less inertia for the cyclist to overcome,
but it may flex more than a heavier one made of the same material. Flexing
the frame wastes energy, most notably in a sprint when the rider tries to
direct as much power as possible to the pedals, where it is transferred
through the chain to the wheels. And yet a stiffer frame, which is also
stronger, is generally heavier and requires more energy for the same acceleration
and speed. Frame builders have also needed to keep the manufacturing process
simple enough for mass production.

After the standard diamond-shaped frame of steel tubes appeared late
last century, the first major breakthrough was in the 1930s, when tubes
made of steel alloys became available. The most successful of these tubes,
still manufactured by Reynolds in England, uses an alloy of steel, molybdenum
and manganese. The ends of the tubes, where stresses are greatest, are thickened,
or butted; they are joined using tubular sockets called lugs, which are
brazed. Many riders in this year’s Tour will be riding bikes with steel-alloy
tubing, such as that made by Reynolds, or by Columbus of Italy, which uses
chromium instead of manganese in the alloy.

More recently, some manufacturers have begun to use aluminium alloys,
which are even lighter, even though these alloys have two major drawbacks.
The first is that welding weakens an aluminium alloy. Manufacturers can
glue the tubes together instead but the process, borrowed from the aerospace
industry, requires strong adhesives and particular care. As a safety precaution,
manufacturers tend to thread the tubes and lugs to make the joints more
secure. The entire process is an expensive one.

The second drawback is that aluminium is not as good as steel at withstanding
the cyclic stresses that are imposed on a frame when a bicycle is ridden,
such as the repetitive bending and stretching of the tubes that cause fracture
with time. These so-called fatigue stresses mean that cyclists should change
aluminium-alloy frames more frequently than steel-alloy ones, even though
the two types of frames may be designed with the same rigidity and strength.

Tubular frames made of composite materials will also appear in this
year’s Tour de France. Some manufacturers, including Look from France and
Specialized from the US, have already produced carbon-fibre tubing, which
comprises a fibrous mesh of carbon impregnated with a resin. Look’s latest
frame uses ceramic fibres to reinforce a braided structure of carbon fibres
and Kevlar; the tubes are glued together at the aluminium lugs.

Every manufacturer likes to claim that its frames for the 1990 Tour
de France are unique and the best available, whether they are made from
steel alloys, aluminium alloys or composites of carbon fibres and ceramics.
Whatever the differences between frames, they will all have at least two
things in common: every frame is a compromise and every one is expensive.
A carbon-fibre frame will cost around Pounds sterling 400. While this is
not a problem for top racing teams, frame manufacturers use the Tour to
advertise their products, and one of their greatest challenges is to design
a high-performance frame that can be mass produced cheaply. This is not
an easy task with steel alloy frames, for instance, where brazing the tubes
together is a highly skilled task best done by hand.

Bikes from the sea

The challenge was taken up by Frank Kirk. After many years as a design
engineer in the automotive and aerospace industries, Kirk knew about the
manufacture of lightweight components produced by die-casting magnesium
alloy. In 1983, he saw the potential for applying this technology to one-piece
bicycle frames. Although magnesium is one of the lightest metals, lighter
than aluminium, it is only one-fifth as strong as steel in tension. Kirk
saw that the tubes would have to be thicker than usual; but he also saw
that if manufacturers could cast a frame as one piece in a mould, designers
would not have to compromise between a frame’s strength, stiffness and weight
to meet the demands of joints between tubes. Where tubes meet, for instance,
the material is often thickened to compensate for the great stresses in
this region, the inherent weakness of the joint and to enable the joint
to be made. Kirk uses a computer to design his one-piece frames. The cross-sectional
areas of the frame’s crossbar and other supports vary according to the strength,
stiffness and weight demanded.

Magnesium frames may not look very pretty, admits Kirk, but they are
much easier and cheaper to produce, he adds. Kirk claims he can mass-produce
a frame that matches the performance of the best aluminium alloy, steel
alloy or composite designs, but costs less than half as much to make. The
material is readily available – a Kirk frame uses the magnesium extracted
from just one cubic metre of seawater. Norsk Hydro, the giant Norwegian
company that put up the money to enable Kirk to mass-produce his frame,
supplies a quarter of the world’s demand for magnesium by extracting the
metal from seawater.

Towards the end of this year at his factory at Chelmsford, Essex, Kirk
plans to begin to operate a 650-tonne die-casting machine, designed by him
and built by Oscar Frech of Stuttgart. He says the machine is the largest
of its kind in the world and can turn out 70 frames an hour. A smaller machine
produced the experimental frames for this year’s Tour.

Among the bicycle components from which designers have tried to squeeze
more efficiency are gear mechanisms and pedals. The driving force behind
the redesign of gears over the past five years has been the popularity of
the mountain bike, or all-terrain bicycle – that stocky, rugged machine
with a tough, heavy frame and fat, knobby tyres, which are meant to allow
a cyclist to ride anywhere. ATBs now account for more than half of all new
bicycles sold worldwide.

Riding a bicycle through swamps or up semi-vertical slopes, however,
demands far more of the gears than conventional designs could provide. Cyclists
need more gears and they must be able to change them more smoothly and precisely.
Most importantly, they must be able to make the changes while they are exerting
as much power as they can on the bike. In the past, riders had to change
gears gently to avoid damaging the mechanism or ‘slipping’ out of gear completely.
Four years ago, Shimano, a Japanese manufacturer, developed the first mechanism
to meet this demand for derailleur gears.

The modern derailleur gear, invented in 1930 by Tulio Campagnola, an
Italian racing cyclist, uses a sprung metal arm to move the chain continuously
over different-sized cogs on the back wheel. Having two derailleurs enabled
racing bicycles to have 10 or 12 gears – an arm by the rear wheel moved
the chain over a block of five or six different-sized cogs, while an arm
near the rider’s feet could switch the chain over one or two much larger
front cogs, known as chainrings. In the early 1980s, improvements in design
led to 14 gears being commonplace.

Shimano’s so-called ‘indexed system’, in which a series of notches controls
the movement of the sprung metal arm, replaces the continuous motion of
the traditional derailleur with precise little jumps that enable the chain
to click into place over each cog. The company modified the profile of some
of the ‘teeth’ on each cog to ensure that the chain clicks smoothly into
place, even when a rider is pedalling at full power. These modified teeth
are shorter than others and act as ‘gates’ for the chain to pass through.

Shimano designed this first system, known as Hyperglide, for the rear
cogs of mountain bikes; it was quickly adapted for road bikes. This year,
Shimano has modified the system to work with the front gear changer; the
teeth of the chainrings are shorter where the pedalling pressure is least,
which is when the feet are at their highest and lowest points.

Although the new system is a simple one, it could mean the few seconds
difference between winning and losing a professional race – or not grinding
to a halt halfway up the face of a quarry. Furthermore, the extra manufacturing
precision demanded of indexed systems allows eight cogs to be squeezed onto
the back wheel, which gives the modern racing bike 16 gears. There is one
drawback, however. Although the shorter teeth do not hinder the normal function
of the gears, some cyclists find that the system is difficult to adjust.

Shimano’s latest innovation for racing bikes is a modification to the
brake levers on the handlebars so that they also control gear changes. It
means that cyclists do not need to move their hands from the handlebars
to change gear (usually, the gear levers are located on the frame), which
disturbs their riding position. Cyclists squeeze the levers in the usual
way when they want to brake and they move them sideways when they want to
change gear; the right lever causes the rear derailleur to shift the chain
to a lower gear and the left lever does the same to the front derailleur.
To change up a gear, cyclists press smaller, secondary levers behind the
main ones. At the moment, the equipment is available only to the top racing
teams.

The dual control lever is connected to a new type of brake calliper
that has two pivots instead of the usual one. This reduces the distance
the brake cable must move to stop the wheel and, according to Shimano, provides
30 per cent more stopping power. This means that reckless competitors can
delay braking as they propel themselves down Alpine passes at speeds of
more than 100 kilometres per hour.

Pedals, like transmissions, have also changed radically during the past
five years. At the beginning of this century, professional cyclists discovered
that they could go faster if they taped their feet into the pedals of their
bikes. This almost doubled the efficiency of the pedalling motion by allowing
a forceful upstroke as well as a forceful downstroke, and led to the invention
of the toe-clip and strap to hold the foot securely to the pedal. Rigid
shoes with notched plates on their soles to keep the shoes in place improved
efficiency further.

But toe-clips have three drawbacks. They loosen at inconvenient moments,
such as during a sprint of racing cyclists, leaving the unlucky rider some
way behind. Furthermore, tight straps are painful and restrict the flow
of blood around the foot. Most importantly, they are dangerous; toe-clips
cannot be unbuckled quickly in an emergency, which makes them potential
death traps.

Over 80 years, manufacturers used lighter, stronger materials, such
as anodised aluminium and titanium, though this overcame none of the drawbacks
of the toe-clips – the basic Victorian design of a cage and strap persisted.
It was not until 1985 that the first pedal overcame the drawbacks of the
traditional toe-clip. The prototype was heavier than professional cyclists
were used to, but it marked a significant development. A year earlier Bernard
Tapie, a French industrialist and a cycling fan, bought the company Look,
a French manufacturer of ski-bindings based in Nevers. He encouraged one
of the firm’s engineers, Michel Beyl, to come up with a new pedal that worked
like a mini ski-binding. Beyl designed a plate that fixed to the rider’s
shoe before locking into the pedal. A sideways flick of the foot released
the foot from the pedal; and the foot was unlikely to be released inadvertently
because the sideways flick is not a normal pedalling movement. There is
also no toe-strap to constrict the foot.

Pedals for safe success

Bernard Hinault, leader of the cycling team sponsored by Tapie, La Vie
Claire, used the first Look safety pedal in the 1985 Giro d’Italia, which
he won. Hinault even claimed that the pedals saved him from a nasty accident
when the bunch of cyclists he was racing with crashed; he saw the accident
coming, unclipped his feet and kept his balance as riders fell around him.
Later that year, Hinault went on to win his fifth Tour de France.

Most racing cyclists prefer clipless pedals, which are more comfortable
and a little more efficient than the old cage and strap. This is because
manufacturers can design their clipless pedals so that the rider’s feet
are directly over the axis of the pedal crank, which helps to ensure that
more power is transferred to the chain. In this year’s Tour, every competitor
will use an up-to-date version of the 1985 prototype.

One of these is the ‘Time’ pedal, also designed by Beyl, that allows
the foot to swivel a few degrees. The swivelling reduces the risk of injury
to knee tendons, a common problem for cyclists that can require major surgery.
Beyl claims that this mechanism does not reduce a rider’s efficiency, although
the pedal is the heaviest and most complicated of the 20 or so clipless
designs now available.

The simplest safety pedal is a cylinder that connects to the rider’s
shoe by a crescent-shaped clip on the sole. Known as the ‘Aerolite’, the
pedal was developed in 1988 by the American manufacturer of the same name.
The pedal uses bearings similar to those in wing components of Boeing aircraft.

In their quest to wring the last ounce of efficiency from racing bikes,
designers have produced more complex gear mechanisms, pedals and frames.
Much of the latest bike technology will not be revealed until the Tour is
over, and most of it will be too expensive to incorporate in models on sale
to the public. There is no limit to the money available to develop the perfect
machine for the top racing cyclists – not when the prize is the chance to
keep the yellow jersey, the ‘badge’ of the leading rider, and to win around
FF2 million (Pounds sterling 200 000) plus several million pounds from subsequent
advertising contracts.

* * *

The mixed blessings of keeping a low profile

IN THE 1984 Olympics, track riders used a new kind of bicycle with a
sloping frame and a smaller front wheel. Called ‘low profile’ bicycles,
these machines were much faster than conventional road-racing bikes because
they made competitors more compact, thereby reducing the wind resistance
that every rider must overcome.

For some of the bikes, aluminium-alloy or carbon fibre discs replaced
the spokes in both wheels. These discs helped the bicycle to go even faster
in two ways. They made the wheels heavier and act as flywheels, conserving
momentum. Secondly, the surface of the disc created less drag than 24 spokes.
These bikes are ideal for steady pedalling at a constant speed.

So, if low-profile bikes with disc wheels are much faster than conventional
road machines, why are they not used in every race? First, a low-profile
bike is more difficult to steer if a rider is changing position constantly
– and in a mass start, which is the case for most stages in the Tour de
France, riders are frequently adjusting their positions to suit the conditions
and the race. Secondly, low-profile bicycles do not corner as well as conventional
bikes, especially if disc wheels are fitted. The problem is that a disc
wheel is completely rigid, whereas a spoked wheel can bend sideways slightly.
This lateral movement helps to prevent the tyre from skidding – the flexing
absorbs some of the centripetal force generated as a rider banks hard into
a bend. Some Tour riders, however, still use disc wheels with a conventional
racing frame.

Low-profile bikes may be more energy efficient than traditional ones
but this is not always what professional cyclists need. In terms of energy
expenditure, the best way to ride is at an even pace, which is how riders
will pedal in the five time-trial stages of the Tour, when individual riders
race against the clock. This might suit low-profile bikes if the route was
straight and smooth. However, when riders race directly against one another,
which is what they will do on most of the stages of the Tour, the pace is
erratic. This is because of the slipstream effect.

A rider pedalling in the wake of a cyclist at the front of the bunch
will use up to 50 per cent less energy than the leader. In the middle of
a bunch of 200 riders, the slipstream effect gives riders a tremendous advantage,
allowing them to conserve energy. If a competitor wishes to escape from
the bunch, the rider must dart out from the group quickly, and rapidly open
up as big a lead as possible.

The key to the success of such an attack is in preventing rivals from
chasing into the new slipstream. If more than one rider escapes, then the
breakaways will often cooperate to stay away from the bunch.

A race will comprise many such attacks and a low-profile machine, while
faster than a conventional bicycle in perfect conditions, lacks the responsiveness,
versatility and cornering necessary for a successful break.

Richard Gould is a keen cyclist and amateur racer. He is also an environmental
scientist with CES, a British firm of consultants based in Manchester.