Note: Descriptions are shown in the official language in which they were submitted.
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Background of -the Invention
The present inven-tion rela-tes to motorcycle
tires having curved, swept-back profiled grooves
that in the 7enith portion extend at a smaller
angle relative to the circumferential direction of
the tire than -they do in -the edge por-tions of the
tread. The profiled grooves are disposed in a left
hand and right hand portion of the tread, wi-th some
of the non-adjacent ones of the profiled grooves of
a given tread portion being interconnected by
connecting grooves, which are disposed in the
zenith portion, to form inclined U-shaped grooves.
Disposed within each U-shaped groove are further
profiled grooves that are isolated from all other
grooves, with the U-shaped grooves of the left hand
portion of the tread being offset from the U-shaped
grooves of the right hand portion of the tread.
Such a tire, despite a relatively low negative
fraction, which permits soft and hence readily
bonding rubber mixtures, also permits a favorable
poæitive frictlonal connection in the longitudinal
direction, in other words to transmit braking and
acceleration forces, even on wet roads. ~lowever,
the transmission of la~eral forces on wet roads
does not yet seem to be optimum. This is perceived
particularly when brief lateral wind blasts are
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encountered, such as occurs, for e~ample, when one
leaves the sheltered side after passing a truck.
The inventive tire differs from the known
tire, where none of the ad~acent, curved, swept-
back profi.led grooves oE a given tread half are
interconnected by connecting grooves that are
disposed in the zenith portion, so that with the
known tire no inclined U-shaped grooves are
provided. With a comparable support or contact
surface and a comparable negatlve profile fraction,
the water displacement capacity of this known tire
is less than that of the general inventive tire,
because all of the profiled yrooves of the known
tire are embodied as blind grooves in the zenith
portion; in other words, the grooves end in the
zenith portion, so that the water that is flowing
along these grooves accumulates or backs up at this
location since it cannot flow off any further.
It is therefore an ob~ect of the present
invention to further improve the lateral force
stability of motorcycle tires of the generally
described inventive type when the angle of tilt is
somewhere in the vicinit~ of 0.
Brief Description of the Drawings
This ob~ect, and other ob;ects and advantages
of the present invention, will appear more clearly
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from the following specification in con~unc-tton
with the accompanying schematic drawings, ln which:
Fig. 1 shows a portion of one
exemplary embodlment of an
inventive front tire tread
configuration, and
Fig. 2 shows a portion of one
exemplary embodiment of an
inventive rear tire -tread
'10 configuration.
Summary of the Invention
l'he motorcycle tire tread of the present
invention is further characterized in tha-t all of
the grooves of the left hand -tread portion are
isolated from the grooves of the right hand tread
portion. With this inventive tread configuration,
in the contact surface region no water can surmount
the center line of the tread. rrhis means that none
of the water displaced in the left hand portion of
the tread can flow over to the right hand portion
of the tread; conversely, no water that has been
displaced by the right hand portion of the -tread
can flow over to the left hand portion of the
tread. Consequently, when transverse slippage or
drift occurs, as is unavoidable whan lateral forces
are transmitted, no sliding in the axial direction
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is associa-ted with the gradual sliding in the
circumferential direction beyond the traveling
speed. In this way, at less of a tilt angle
inventive tires permit grea-ter transverse Eorces to
be transmi-tted than was previously possible. This
advantage becomes particularly effective on wet
roads while traveling straight ahead when brief,
savere wind gusts act upon the motorcycla driver.
In contrast to a steady travel in curves, the
transverse forcas tha-t are necessary for a very
rapid reaction are transmitted at an only slight
angle of tilt, approxlmately ~ 15.
In contrast to tires of the aforementioned
general type, the basic differ0nce is that the
negative profile fraction of the inventive tires in
' the zenith portion is at least 30~ greater than in
further axially outwardly disposed tread surface
portions. At the same time, the number of block
edges in the zenith portion that extend in the
circumferential direction is increased, 80 that in
contrast to this aforementioned type of tire there
is also achieved an increased transfer of
transverse forces on wet roads with slight tilt.
The advantages of the inventive profiling or
configuration of motorcycle tire treads with regard
to steering precision on we-t roads are achieved
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without drawback with th~ transfer of longitudinal
forces.
Especially with regard to -the front tires, it
is desirable that -the connecting grooves, which
in-terconnect non-ad~acent ones of the curved,
swept-back profiled grooves of t}-e same tread half
portion, ex-tend parallel to the circumferential
direction of -the tire. It is also advisable with
front tires that the curved, swept-back profiled
grooves be directed counter to the direction of
forward travel.
In contrast, for large-volume tires,
especially with respect to the rear tires, it is
expedient to dispose the connecting grooves at an
angle of 30 to 60 relative to the circumferential
direction of the tire. In -this way, a lesser and
more gradual reduction of the negative profile in a
direction -toward the axial tread edges is achieved.
With rear tires, it is advisable that the curved,
swept-back profiled grooves be directed in the
direction of forward travel. The reason for this
is that rear motorcycle tires primarily hav0 to
transfer positive drive forces in the longitudlnal
direction, while the braking forces hardly play any
role at the rear tire due to the high center of
gravity relative to the wheel base. With the front
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tire, the opposite appli0s, as is known.
In the context of the present appliaati.on, the
designation "U-shaped groove" refers -to the
combination of three interconnected profiled
grooves, and in particular the interconnection of
two swept-back grooves via a furth2r groove that
extends transverse thereto and that within the
context of the instant application is designated a
connecting groove. The resul-t, when viewed in a
drawing, is a configuration that has a shape of the
letter "U".
It has proven to be advantageous to
respectively dispose between the various U-shaped
grooves of a given tread portion either one or two
further curved, swept-back profiled grooves that
are isolated from all other grooves, i.e. do not
communicate with any other grooves. For the
filigree-like tread configuration of the front
tire, it has proven to be advantageous to dispose
~ust one further curved, swept~back profiled groove
between the respective U-shaped grooves, whereas
for the larger-surface tread profile of the rear
tire it has proven to be advantageous to dispose
two further curved, swept-back profiled grooves
between respective U-shaped grooves.
Regardless of the intended use of the front or
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r~
rear tire, i-t has proven to be advan-tageous to
dispose within each U~shaped groov~ one further
curved, swept-baclc profiled groove that i8 isolated
from all other grooves. In this way, an
advantageous length of the connecting groove
relative -to the length of the contact surface is
achieved.
With the tread configuration of the front
tire, it has been shown to be important for the
connecting grooves of the left hand and rlght hand
tread portions to alternate over the circumference
of the tire in such a way that at each
circumferential location, a connecting groove is
present righ-t next to the zenith portion. This
advantageous configuration results if, as
previously described, the number of further,
isolated profiled grooves within the U-shaped
grooves coincides with the number of further,
isolated profiled grooves disposed between the U-
shaped grooves.
Further specific features of the presentinvention will be descrlbed in detail subsequently.
Descrlption of Preferred Embodiments
Referring now to the drawings in detail, in
both the exemplary embodiment of an inventive front
tire configuration as shown in Fig. 1 and in the
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exemplary embodiment of an inventive rear tire
con~igura~ion as shown in Fig. 2, the raspective
tires are designated by the reference numeral 1.
The profiled or shaped grooves are indicated
generally by the reference numeral 2, followed by a
decimal and further numbers to differentiate the
various grooves from one another. For example, 2.0
designates the isolated profiled grooves that are
surrounded by a U-shaped groove 10, with 2.10
designatlng the profiled grooves that are a part of
the U-shaped grooves 10. Thus, the isolated
profiled grooves that are disposed within the U-
shaped grooves 10 are designated 2.0, while the
isolated profiled grooves ~hat are disposed between
two ad;acent U-shaped grooves of the same row are
designated with the reference numeral 2.1.
In both Figs. 1 and 2, the zenith or center
line of the tire is designated by the referençe
numeral 3. The zenith portion 9 that is disposed
about the center line 3 includes the connecting
grooves 8. Thus, the zenith portion 9 belongs
partly to the left row or tread half 6 and partly
to the right row or tread half 7. In Fig. 1, the
boundary between the left and right rows extends
linearly along the center line 3, while in Fig. 2
this boundary follows the wavy dot-dash line 13
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wi-thln the zenith portion 9. The critical feature
that is common to both embodiments is that the
boundary between the left and rlght rows
exclusively follows a positive course, i.e. does
not cross or is not tangential to any grooves,
which in the terminology of the art would designate
a negative course.
In the edge por-ti.ons 4 of -the tread 5, it is
expedient that not all of the ends of the profiled
grooves 2 be aligned with one another; if the ends
of the grooves are offset slightly relative to one
another, passing over the holding or transition
boundary when tilti.ng or banking is too great is
less abrupt.
The profiled grooves 2 e~-tend more steeply in
the zenith portion 9. In other words, in the
zenith portion 9 the profiled grooves 2 form a
smaller angle oc with the circumferential
direction C (the center line 3) than they do in the
edge portions 4 of the tread 5.
In both Figa. 1 and 2, the direction of
forward travel is indicated by an arrow 11 near the
bottom of the page.
Mow that the features common to both
illustrated embodiments have been described, the
features that are dlfferent ~or -the two preferred
g
ambodiments will be described.
With the con~igura-tion for ~he front tire
illustrated in Fig. 1, the direction of rise or
sweep-back o~ the confi~uration is contrary to the
direction of travel 11.
In contrast, in the rear tire illustrated in
Fig. 2, the direction of rise or sweep-back of the
configuration is in the direction of travel or
orientation of rotation 11. Whereas with the front
tire of Fig. 1 only a single isolated profiled
groove 2.1 is disposed between the various U-shaped
grooves 10, in the rear tire configuration of Fig.
2, two isolated profiled grooves 2.1 are disposed
between tha various U-shapsd grooves. The
preferred embodiment of the inventive rear tire
configuration illustrated in Fig. 2 shows tha-t the
connecting grooves 8 are disposed at an angle of
inclination B of between 30 and 60 relative to the
circumferential direotion C, whereas in the
embodiment of the front tire illustrated in Fig. 1,
the connecting grooves 8 extended parallel to the
circumferentlal directlon C. Furthermore, in the
preferred rear tire profile o~ Fig. 2, the angle of
inclination ~ of the connecting grooves 8 in the
zenith portion 9 corresponds to the angle of
inclination ~ of the closest ad~acent leg 2.12 of
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the next ad~acent proEiled groove 2.10 of a U-
shaped groove 10. Th~s wattlework-like
configuration enables no-t only an increased abillty
to transmit lateral forces, but at the same tlme
enables a high transfer of longitudinal forces.
The inventive motorcycle tire configurations
are particularly suitable for heavy motorcycles
used on -the road, and for racing machines on wet
stretches.
The present invention is, of cvurse, in no way
restricted to the specific disclosure of the
specificatlon and drawings, but also encompassas
any modifica-tions within the scopa of the appended
claims.
