As I had mentioned in the earlier article on Yamaha FZ16 Midship Muffler, here is the next piece of content on the bike’s radial tyre. If you want to read the original review visit, Yamaha FZ16 Road Test and Review.
The Radial Tyres of Yamaha FZ16: This
is the first radial tyre ever featured as a standard equipment on a
bike in India. A radial tyre has a construction in which the cords of
the structural structural skeleton of the tyre, known as the carcass,
run radially around the tyre at right angels in the direction of forward
motion. The structure gives the tyre excellent firmness and prevents
excessive distortion of the tyre’s shape due to forces from the road,
reduces rolling resistance and helps improve fuel economy. Most people
know the heavy, woobly feeling while riding on a bicycle with low air
pressure in the tyres, and when the tyres are fully inflated there is
little distortion in its shape, even when going over bumps on the road
surface. That is what is meant by low rolling resistance.
We asked the Yamaha engineers about the
actual user benefits that comes from this radial tyre. “The FZ16 has
been developed with the aim of going beyond the conventional commuter
bike to achieve true sports bike performance that offers the owner real
fun of riding. As one of the ways to achieve this goal, we adopted a
radial tyre for the excellent firmness it provides. To optimize, the
balance between the tyres and the frame, we also adopted an extra sturdy
front fork with thick 41mm diameter inner tubes.” We began by asking
about more detail on the merits of a radial tyre. “Because of its
excellent rigidity, a radial tyre can be designed with less tyre height.
And because the tyre is thinner and flatter, it weighs less. The size
of the radial tyre on the FZ16 is 140/60-R17, compared to an equivalent
120/70-17 bias tyre. And, although it has roughly the same diameter, it
weighs less than the biastyre. This also means lower inertial mass at
the rear axle. You might compare this to the feeling of wearing light
sneakers as opposed to heavy shoes.
Another benefit of radial tyres is that
their added firmness means that even a fatter tyre provides a firm ride
with a sharp handling response. Generally speaking, a fatter tyre tends
to flex under pressure and therefore does not give a sharp handling
feeling. But a radial tyres inherent firmness means that even a fatter
tyre there is a quicker convergence of external forces, which means
sharper handling and a sportier, more agile ride. It is a tyre that
provides a solid feeling of road contact.
To develop the radial rear tyre for the
FZ16, Yamaha’s design staff worked closely with the technical staff of
the tyre maker MRF and exchanged information numerous times about the
exact performance qualities they wanted for this model. The
specifications of a custom designed tyre like this involves more than
just the various size dimensions. This also involves longitudinal and
lateral rigidity balance, grip qualities and flexing (distortion)
characteristics and a mutual balance amongst these various factors. Of
course, it is not this tyre alone that gives a bike like the FZ16 a
sporty, agile ride. Adjustment of the specs of the various chassis
components to achieve an optimum mix is also necessary to bring out the
maximum performance potential. Here is what the Yamaha engineers had to
say about the chassis development: “The FZ16 frame is a newly developed
diamond type frame. Viewed externally, it may look similar to the frame
of the Yamaha Gladiator, but in fact it is completely different and was
developed wfth a prime focus on reducing weight. Also, rigid mounts were
used instead of rubber mounts in a design that makes the engine
function as a structural member of the frame.
Then we worked on achieving the best
specs for the many related parts and components in detail, through
repeated tests. The stay that holds the engine (cylinder) head to the
frame are made of steel plate with a thickness of 3.2 mm and
high-rigidity die-cast Aluminum was used for the parts that connect the
pivot assembly to the frame. These parts are especially effective in
providing quicker convergence (absorption) of external forces when
running at higher speeds. Also, a hard rubber close in consistency to
plastic resin is used for the rear hub damper to increase rigidity. This
combines with the effect of the rear radial tyre to make this a machine
that achieves excellent response to the rider’s handling actions.
In simple terms, you won’t feel any
“sloppiness” in the handling response while riding through traffic on
the city streets. Instead, you get a response that enables agile riding.
The FZ16 has a chassis performance that provides direct response to the
rider’s throttle work, and at Yamaha we call this, “drivability with a
feeling of directness.” And it is part of their definition of the fun of
riding that they want this model to deliver. Another important chassis
feature of this model is the extra sturdy front fork with thick
4lmm-daimeter tubes. The 41mm inner tubes of this front suspension are
the size usually used on 400cc class sport bikes. Why did Yamaha choose
such a high-spec unit? “Besides, its shock-absorbing function, the front
fork is also a component that determines the overall rigidity of a
motorcycles chassis. To achieve the optimum balance with the new frame
and the radial rear tyre, we chose a unit with 41mm tubes to achieve a
high level of rigidity.
In addition to providing good rigidity
and stability in straight-line running, it also functions especially
well to give a good, solid feeling of machine stability on rough roads
with continuing bumps and during sharp braking,” the Yamaha engineers
comment. That’s not to mention the distinctive look it gives to the
bike’s appearance. And, the larger spec also improves the fork’s
suspension function. “These thick inner tubes improve the mechanical
functioning of the suspension. If you have two suspension units with the
same cushioning capacity, the one with the larger inner tube
circumference will function better, because the increased surface area
reduces the friction per unit of surface area and thus produces better
response. Of course, the larger diameter also means that you can give it
a larger diameter spring as well. With the FZ16s front fork you wont
feel any “bottoming out” when going over bumps or during sudden braking
because of the strong, solid cushioning function it delivers”.
The fatter fork may look heavier but
that is only the visual impression. “This fork uses tubes with thinner
walls to reduce weight, and the handlebar crown that supports the fork
is also a lightweight cast Aluminum unit. The design of the ribs on the
inside of this crown was also optimized by conducting repeated tests.
The specs of the fork offset, caster and trail were also optimized in
relation to each other to help contribute further to the enjoyable and
highly stable handling feeling”. Another characteristic you will notice
with the handlebar crown and the under-bracket on the FZ16 is the wider
breadth of their span. They are about 10mm wider than those on the Gladiator and this surely contributes to the stability of the front assembly.
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