This is the first in a number of articles exploring motorcycle tire basics plus various basic dynamic characteristics of the particular handling behavior of motorcycles. Overall this kind of is an extremely complex subject
and needs a good levels of mathematics and physics effectively understand what's happening.
Even so, in these content articles I'll try plus explain the principles with the total minimum of arithmetic,
but where this is unavoidable Items not exceed simple trigonometry. For those that are miserable
with any arithmetic whatsoever, don't be anxious, just skip those parts and the rest should even now prove useful.
I will try and show the mechanics with many sketches and graphs.

It seems amazing that just two small contact areas of rubber, can easily support our devices and
are able to offer large amounts associated with power to the road, whilst from the same time supporting cornering
makes at least around the weight of the bike and rider. Therefore the particular tires exert maybe the single
most important influence over general handling characteristics, so that it seems appropriate to study their
characteristics before the other various areas of chassis design.
If Newton first expounded to the world his theories associated with mechanics, no question he had on his mind,
things apart from the interaction of motorcycle tires with typically the terrain. Never-the-less his
suppositions are equally valid for this specific situation. In particular his third law states, "For every pressure there
is definitely an equivalent and opposite power to resist that. " or to place it another approach "Action and effect are equal in addition to
opposite. "

Related this to wheel action, means of which when the car tire is pushing on the highway then the path is pushing
back again equally hard about the tire. This particular applies equally good regardless of whether or not we are looking from
supporting the weight involving the bike or resisting cornering, braking or driving masses.
What this special law of Newton does not concern on its own with, is which force is the particular originating one nor
indeed would it subject for many purposes of analysis. However, like a guide to the particular knowledge of
some bodily systems it will be often useful to be able to mentally separate the particular action from the particular reaction.
The causes that occur among the ground and the tires determine so much the behaviour of our
machines, but these people are usually taken for granted. tires really perform these kinds of a large number of different
duties and their apparent simpleness hides the diploma of engineering elegance that goes in to their
design and fabrication. Initially pneumatic tires were fitted to improve enjoyment reduce loads in
the wheels. In spite of modern suspension techniques it truly is still typically the tires that offer the first type of
defence for absorbing road shocks.
To explore carcass construction, tread compound and tread pattern in fantastic detail is over and above the scope
of this book. Rather we are concerned here which includes basic principles and even their effects on handling
characteristics.

Excess weight Support


The most obvious purpose of the wheel is to assistance the of the particular machine, whether upright or
leaning above in a nook. However , the genuine mechanism with which the particular air pressure plus tire passes
the particular wheel load towards the road is often misunderstood. Consider fig. 1, this draw represents a slice
with the bottom regarding a rim and even tire of unit thickness by having a pumping pressure of S. The left
side shows the steering wheel unloaded and the correct hand side exhibits it supporting the particular weight F. Any time
loaded the tire is compressed top to bottom and the thickness increases as shown, perhaps surprisingly typically the
internal air strain does not modify significantly with insert, the internal volume is usually little changed.
From the widest part (X1) of the not loaded tire the internal 1 / 2 width is W1, and so the force normal in order to
it due to the internal strain is simply 2. P. W1. This force acts up-wards towards wheel
edge, but as the strain and width of tire are evenly distributed around the circumference the overall
effect is completely well-balanced. This force also has to get opposed by an equal stress (T) inside the tyre
carcass.

The filled tire provides a 50 percent width of W2 at it's largest section (X2) and so the normal force is a couple of. P. W2.
Consequently, the extra force more than it, when loaded, is 2. G. (W2 - W1) but as the tire is just
widened over a small part of the bottom part part of the circumference, this force supports the load F.
The particular above describes how the inflation pressure and even tire width increase produce forces in order to oppose the
top to bottom wheel loading, but does not completely make clear the detail regarding the mechanism simply by which these
pushes are transferred in order to the rim. The bead of a fitted tire is an interference fit over the bead couch of
the tire rim, which places this area in to compression, the in-line component of the side-wall anxiety
due in order to the inflation stress reduces this compression setting somewhat. This aspect is shown while F1 on
the particular unloaded half regarding F1 = To. cos(U1). The higher angle U2 involving the side-wall any time loaded means
that this in-line component associated with the tension is reduced, thus also restoring some of the rim to tire
bead compression. This kind of only happens within the lower part involving the tire circumference, where the extending
takes place. So we have a nett raise in the compressive force for the lower rim acting way up, this
supports typically the bike weight. The nett force is definitely the difference involving the unloaded and even loaded in-line
forces,

F = To. (cos( U1) -cos(U2))

The left edge indicates half of a great inflated but
not loaded tire, a stress (T) is made inside the carcass simply by
the interior pressure. To the right, typically the compressed plus
widened shape of the particular loaded tire will be shown.

Suspension Activity

In performing this kind of function the pneumatic tire is typically the first object of which feels any highway shocks and so acts
as the utmost important element in the machine's suspension system. For the extent of which, while
uncomfortable, it would be pretty feasible to trip a bike around the roads, at fair speeds with no
other form of bundle absorption. In truth rear suspension was basically not by any means standard until the 1940s or 50s.
Whilst, regardless of the particular sophistication in the conventional suspension system, it might be quite
impractical to use wheels without pneumatic tires, or several other form associated with tire that authorized
considerable bump deflection. The loads fed into the tires without such auto tires can be enormous in
all but slow speeds, and continual tyre failure would be the norm.
Some figures will show what I mean: --Assume that the motorcycle, with a typical size front steering wheel, hits a twenty five
millimeter, sharp edged bump at 190 km/h. This not just a large bump.
With no wheel the wheel would likely then be subject matter to an common vertical acceleration of approximately
1000 H. (the peak worth would be above this). This means than if the particular wheel and brake
assembly a new mass of 25 kilogram. then the regular point load around the rim would turn out to be 245 kN. or perhaps about 25
plenty. What wheel could stand that? In case the wheel was shod with a normal tire, then this would likely have at
ground level, a spring price, to a well-defined edge, of around. 17-35 N/mm. The maximum force next
transmitted for the tire for a twenty-five mm. step can be about 425-875 N. i. e. less than four thousandths
of the previous figure, and this load would be more evenly spread around the rim. Without the tire the
shock loads exceeded back to the particular sprung part regarding the bike would likely be much larger too. The straight tyre
velocity would likely be a lot better, and so the particular bump damping makes, which depend about wheel
velocity, would likely be tremendous. These high forces will be transmitted directly back to bike and rider.
The following five charts show several outcomes of a computer system simulation of accelerations and
displacements about a typical highway motorcycle, and demonstrate the tire's relevance to comfort and street
holding. The bike is vacationing at 100 km/h. and the front side wheel hits a 0. 025 metre high step in 0. 1
mere seconds. Note that the particular time scales change from graph to graph.
Three cases are considered:

� With typical vertical tire stiffness and even typical suspension cropping and damping.

� With identical tyre properties but along with a suspension originate rate of a hundred X that of the previous.

� With tire stiffness 100 X the above and with normal delay, pause springing.

So basically we are considering a typical case, another case with almost no suspension cropping and
the final case is together with a virtually rigid tire. Structural packing, comfort and roadholding would all be adversely
affected without the initial cushioning of the wheel. Remember that the over charts are generally not most to the same amount of time scale,
this is only to better illustrate the appropriate points.

This specific shows the up and down displacement of the particular front wheel. Presently there is little variation between the optimum
displacements for the particular two cases using a normal tyre, for a compact step the front tire absorbs almost all of the impact. Yet ,
in the case of some sort of very stiff fatigue, the wheel movement is increased simply by a factor of approximately 10 times. It is obvious that the tire
simply leaves the ground within this case along with the landing bounces is seen after 0. a few seconds.

These shape show the up and down movement of the particular C of Gary the gadget guy of the cycle and rider. Just as Fig 1 it is clear that typically the stiff tire
will cause much higher bike actions, towards the obvious loss of comfort.

Representing the different accelerations transmitted towards the bike plus rider, these curves show the vertical
accelerations with the C regarding G. Both regarding the stiffer tire or stiffer delay, pause cases show comparable values of around five or 6 times
that of the standard case, but the shape of the two curves is very different. With all the hard suspension there is certainly bit of
damping and that we may see that this needs a few process to be in down. The particular second bump at around 0. 155 seconds is any time the
rear tire hits the stage, this rear wheel response is not really shown on the particular other graphs regarding clarity.

Front wheel vertical acceleration for that two cases using a normal tire. The early part is identical for your two situations,
the suspension offers little effect right here, it is tire deviation this is the most essential for this height of step. Just as Fig 5 typically the
lack of suspension damping allows the particular tire to bounce for a few cycles prior to settling down.

Because in these curves are with the steering wheel acceleration, the ideals of the standard case are overwhelmed by the hard
tire case, with a peak worth of close to be able to 600 G as opposed with nearly 70 G normally. Once again note the effects of typically the landing
bounces following 0. 5 seconds. This high acceleration would cause really high structural launching.

As the car tire is indeed good at removing the majority of the street shocks, right at the point of program, perhaps it
would be worth while to consider designing this to absorb even more and eliminate the particular dependence on other
suspension. Unfortunately we would run into other problems. We need all seen big construction
machinery jumping down the path on the balloon auto tires, sometimes this gets so violent that will the
wheels really leave the floor. A pneumatic tire acts just like the air spring, along with the rubber acts like
a damper whenever it flexes, nevertheless when the wheel is made greater the springing effect overwhelms the
diffusing and we then find the uncontrolled jumping. So you will discover practical restraints for the volume of
cushioning which can be built into a tire for any given application.

Check over here of Tire Stress

Obviously, the cropping characteristics mentioned above are largely affected by the wheel inflation
pressure, yet there are various other influences also. Carcass material and building as well as the properties
and even tread pattern regarding the outer layer of rubber just about all have an result on the two cropping properties and
the particular area in make contact with with the earth (contact patch). Under plus over inflation the two allow the tire in order to
assume non-optimum cross-sectional shapes, furthermore the inflation strain exerts an effect
over the spectrum of ankle flexibility of some sort of tire and this is a property of the utmost importance to motor bike
stability. Manufacturers' recommendations should always be adhered in order to.

The influence associated with tire pressure about the vertical tightness of an overpriced tire, when crammed about
a toned surface. pneu camion lourd montreal are from genuine measured data. Take note that the spring and coil rate is near
linear over typically the full range of launching and varies through 14 kgf/mm. from 1. 9 bar pressure to nineteen kgf/mm. at
a couple of. 9 bar. The effective spring charge when the wheel is loaded against a sharp advantage, for instance a brick, is
considerably lower as compared to this, and is a lot more non-linear as a result of modifying shape of the contact area because
the tire "wraps" around the item.

This spring level acts in collection together with the suspension suspension springs and is also an essential part of typically the overall
suspension program. An interesting property of rubber is the fact when compressed and even released it
does not usually return exactly to it's initial position, this will be generally known as hysteresis. This effect is displayed
only for the one. 9 bar. situation, the curve sketched during the loading stage is not followed during the
unloading phase. The area among these two curves represents a reduction of energy which results in
car tire heating and furthermore acts as a type of suspension damping. In this particular particular case the power lost
over a single loading and unloading cycle is about 10% of typically the total stored vitality in the
compressed tire, and is an important parameter handling tire bounce.

Top to bottom stiffness of the standard road car tire against a flat surface at different pumping pressures. This files is from an
Avon Azaro Sport II 170/60 ZR17. Typically the upward arrows reveal the compression regarding the tire and the 2nd line with all the
downward arrow (shown only at one 9 bar regarding clarity) shows typically the behaviour of the particular tire when typically the load is launched. The
shaded area between the a couple of lines represents the loss of strength called hysteresis. This specific acts as a source of suspension
damping and also heats the particular tire. (From files supplied by Avon tires. )

Horizontal stiffness of the same tire proven in fig. being unfaithful. The vertical load was constant at 355 kgf. along with the wheel was
stored vertical. As anticipated the tire will be somewhat stiffer using the higher pumping pressure but will lose grip or saturates at the
lower lateral load associated with 460 kgf. in comparison to 490 kgf. at the lower pressure. (From data supplied simply by Avon tires. )

Contact Area

The tire must ultimately give it's assistance to the bike coming from a small place of rubber talking to the
ground, therefore "contact patch area = vertical power � average get in touch with patch surface pressure". This
applies in any condition.

The contact patch surface pressure is not really however, the similar as the pumpiing pressure, as will be
sometimes claimed. These people are related nevertheless there are at least four factors which modify the relationship.
Carcass stiffness, body shape, surface rubber depth and real softness, and road surface compliance. When
we all have an really high carcass firmness then inflation stress could have a lowered influence.
Let's look at this inside of a little more detail and even see why:

In case a tire was performed just like a good inner tube, that is from quite thin rubber plus with little stiffness unless
inflated, then an internal air pressure would likely be the only means to support the particular bike's weight. In this
case the contact patch pressure would be equal to that of the particular internal air stress. For an atmosphere
pressure of two bar and some sort of vertical load of 1. 0 kN. Then the make contact with area would always be 5003 sq . mm. If we
today increased the atmosphere pressure to say 3 bar the particular area would drop to 3335 sq mm.

Let's right now imagine that we all substitute a rigorous steel tubular baskeball hoop for the rim and even tire, the area in contact
with the ground will be quite small. In case we now blow up the hoop with some air pressure, it will not get
much imagination to be able to see that, in contrast to the inner pipe, this internal pressure will have a negligible impact
on the particular external portion of get in touch with. Obviously, a car tire is not the same as the steel hoop, nor the inner tube,
but this particular does show that will the carcass stiffness can reduce the contact surface place as calculated solely
from inflation pressure alone.

I did so two sets of testing. For the first I kept the tire inflation stress constant at second . 4 bar in addition to varied the car tire
load between a hundred and seventy-eight and 1210 D. (allowing for the particular weight of the particular glass and solid wood beams). Secondly, I actually
keep a continuing insert of 1210 D. and tried varying the inflation pressure between installment payments on your four to 1 bar council.
Even with a new generous allowance for experimental error the effects are clean. The graphs present that
the results came out to fit realistically well to the smooth line, right now there wasn't much scatter.

Point (1) about the curve with constant inflation pressure, shows how a genuine contact patch stress is
lower (just over half) than the inflation strain, or in some other words the contact area is increased. This is
because of the rubber surface complying, thus this is usually essential at decreased vertical loads, while
carcass stiffness became essential as the particular load rose because shown by factors (3) to (6) where the
real contact pressure is usually higher than the particular air pressure, we. e. reduced area of contact.

Dimension setup. Various weights were placed on the end of a beam, which also loaded the tyre via
heavy plate of glass. The beam has been arranged to apply the burden to the tire which has a some: 1 leverage. Thus a 25
kgf. fat would load the tire with 75 kgf. By dating within the glass the contact area
was basically determined.

The leading plot shows the particular measured contact patch pressure at different wheel loads for a constant pumpiing pressure
of only two. 4 bar. The particular lower curves exhibit the contact strain at various pumpiing pressures for the fixed load regarding 1210 N. The
numbers at the data points correspond with the get in touch with area tracings in the previous sketch. The simple line on every single storyline
shows the case from the get in touch with patch pressure getting equal to the particular inflation pressure.

The carcass stiffness really helps to support the equipment as being the air strain is definitely
reduced, the particular contact patch pressure being considerably better than the pumpiing pressure. It looks because
though the a couple of lines will cross at an air pressure of in relation to 3. 5 pub. (although this was not tested by
measurement), at which point the particular surface rubber data compresion will assume the greatest importance.
This is as per the steel hoop example above.

We can easily observe the two distinct effects of surface area compliance and carcass stiffness and precisely how the
relative importance of these varies with load and/or inflation pressure.

These kinds of tests were just done with one particular particular tire, various other types will show different detail outcomes but
the total effects should adhere to a similar style.

Area Under Handling

Does cornering influence tire contact location?
Let's assume a new horizontal surface plus lateral acceleration regarding 1G. Under these conditions the bike/rider
CoG will end up being on the line in 45� to the horizontal and passing through the get in touch with patch. There may a new
resultant push acting along this particular line through typically the contact patch associated with 1. 4 times the supported weight.

This force will be the resultant of the supported weight and the handling force, which have got the same
size, in this example of this of a 45� lean. The power normal to the surface is simply that due to the particular
supported weight and does NOT vary with cornering push. The cornering pressure is reacted by the
horizontal frictional force generated by the tire/road surface area and this frictional force is "allowed" simply by
virtue involving the normal push.

Therefore, into a first approximation cornering push will NOT affect the tire contact location, and in simple fact this
case can be approximated to be able to, if we were just considering the inner tube without an actual tire.
Even so in reality, the lateral force may cause some further tire distortion to take place at the
road/tire interface and based on the tire characteristics, mentioned above, the contact location may
well modify.

Another aspect in order to this features study course the tire cross-sectional profile. The old Dunlop triangular auto racing
wheel, for example, was created to put more rubberized on the street when leant more than, so even without tire
distortion the contact patch area elevated, simply by virtue of the trim angle.