THE IMPORTANCE OF GOOD BRAKES
An analysis of the different braking systems in the three
categories of the World Motorcycling Championship
In an era when many people say that MotoGP riders, limited
by the electronic management of their bike`s power, have little
chance of going a lot faster than their rivals one aspect
that is still crucial when trying to set times that are only
thousandths of a second different is the braking. Brakes are
a very important part of the mechanics on a motorbike and
a comparison between the braking systems in the three categories
allows us to see several differences.
The characteristics of the bikes in the three categories
require different systems, owing to the big differences in
weights, powers and speeds on a motorbike for MotoGP, for
250cc and for 125cc. As Dani Pedrosa, World 125cc Champion,
and two times World 250cc Champion, as well as runner-up in
MotoGP with the Repsol Honda Team last season, explains, “the
starting point for the braking is clearly different in the
three categories, and the weight and the power differences
require different evolutions and innovations in the top category
but these have not been necessary in the two smaller categories”.
The largest most powerful discs are currently in the top category
of the World Championship - MotoGP.
The Repsol Honda RC212V 2008 uses 320mm diameter carbon discs
made by Brembo on the front wheel, this large size is essential
to stop a machine that weighs 148kg and capable of reaching
a top speed of 320km/h. “The most notable quality of
carbon discs is that they operate better at higher temperatures.
This is important because taking into account their braking
power, the steel discs that were used before warmed up and
then lost their efficiency towards the end of the race, and
that could be very dangerous” recalls Pedrosa.
Carbon discs for more braking power
Carbon discs only function well at high temperatures, above
300º C. In fact, when it is very cold a sort of “disc-cover”is
used to maantain an optimum working temperature. The discs
usually last three races, whilst the set of pads only last
one race. When rain falls all this changes, because when the
water makes contact with the disc they are cooled and lose
part of their efficiency. In these cases the carbon discs
are replaced by the traditional steel type, and at the same
time the pads are also different.
Referring to the rear brake, there are various possibilities
depending on the personal preferences of the riders. In Dani
Pedrosa`s case the Repsol Honda Team rider opts for a 200mm
disc, whilst Nicky Hayden uses one of 255mm. This reflects
the different “schools” where they learnt to ride.
Pedrosa learnt in the smaller categories of the World and
Spanish Championships, Hayden was dirt track trained, and
as the American Repsol Honda Team rider says, “there
the motorbikes do not have a front brake and you learn from
being aggressive and by placing the bike by using the rear
brake”.
In the smalller categories, steel discs
In 250cc, the riders opt to use two steel discs at the front,
255mm in diameter, and a single 220mm disc at the rear. This
year the brakes on the KTM have changed and although they
are still made by Brembo, they use a lighter material. Moreover
they are now easier to mount, clean and remove, and the pads
are also easier to replace. The pads are something that can
vary in composition so that they brake more progressively,
that is to say more or less aggressively, along with their
resistance to higher temperatures.
Julián Simón, who changed from the 125cc category
to 250cc last year, emphasises the fact that in his experience,
“the difference in braking power is not so big between
the two categories, because in 125cc the brakes are very powerful.
What varíes is the weight of the motorbike, in 250cc
it is heavier, and this means that a more immediate braking
is necessary than in 125cc”. It is precisely this that
is one of the Repsol rider`s strongpoints, it is always spectacular
to see him reaching the end of a straight to take a corner
at an angle, something he likes “I feel that I take
advantage of the braking power without using the whole lever
movement, I only touch it a little”.
In the 125cc category, the youngest riders in the World Motorcycling
Championship use a single 320mm diameter disc at the front,
and one of 190mm at the rear, with a radial 4 piston pump
and with 4 pads per caliper. The pump has two features that
can be changed, the diameter and the distance, in this case
they are 16x16. If you reduce the distance, it brakes harder;
but if it is longer the rider has to use more force on the
brake lever, as it has less power. If the diameter is modified
you change the feeling on the brake, it is spongier. The pads
working life is just one race. In fact, new ones are usually
mounted for a race and the old ones used for practice in the
subsequent GP. As for the number of discs there are 6 mounted
on the 6 wheels they are allowed, and they last the whole
season.
Evolution in all categories
Since the latest German GP some riders in 125cc have been
using a new system of brakes at the front, with two discs
of 210mm instead of the original 320mm. With this system the
aim is to balance the front end when braking at the entrance
to a corner, stopping the front wheel from moving to the exterior
when the rider is leaning over. Marc Márquez was one
of the riders that tested this new Brembo system in Germany,
although according to the young Repsol KTM Team rider, “there
is still work to be done so as to get more powerful braking
with the two discs, comparing it to the usual system that
we use”.
With world titles in the two smaller categories and a second
placed finish in MotoGP, Dani Pedrosa can evaluate and compare
the distinct braking behaviour with precision. According to
the Repsol Honda Team rider “in all categories a high
braking power is required. In MotoGP you need to feel it with
your fingers, although in 125cc it is also important as the
tyre is much smaller and it is subjected to a lot of power.
Braking continues to be one of the most important factors
in all races.”
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