TIRE WITH A NON-OPEN GROOVE IN THE TREAD

Abstract

The invention relates to a tire whose tread (1) has at least one through groove (3) and at least one non-through groove (4). According to the invention, a non-through groove (4) is filled with a material (9) capable of being completely released during wear of the tread (1), the radially outer surface (6) of a non-through groove (4) being radially outer to the bottom (8) of said at least one through groove (3), when the tire is new. Figure for the abstract: [Fig 1]

Description

Title of the invention: TIRE HAVING A NON-OPEN GROOVE IN ITS TREAD

[0001] The present invention relates to a tire, with a radial carcass reinforcement and more particularly to a tire intended to equip vehicles carrying heavy loads, such as, for example, trucks, tractors, trailers or road buses.

[0002] Generally, in heavy-duty tires, the carcass reinforcement is anchored on both sides in the bead area and is radially surmounted by a crown reinforcement consisting of at least two superimposed layers formed of parallel wires or cables in each layer and crossed from one layer to the next at angles between 10° and 45° with the circumferential direction. These working layers, forming the working reinforcement, may be further covered by at least one protective layer formed of advantageously metallic and extensible reinforcing elements, known as elastic elements.It may also include a layer of low-extensibility wires or cables forming an angle of between 45° and 90° with the circumferential direction. This layer, called the triangulation layer, is radially positioned between the carcass reinforcement and the first crown layer, known as the working layer, which is formed of parallel wires or cables having angles of no more than 45° in absolute value. The triangulation layer, together with at least the aforementioned working layer, forms a triangulated reinforcement which exhibits little deformation under the various stresses it is subjected to. The essential role of the triangulation layer is to resist the transverse compression forces exerted on all the reinforcing elements in the crown area of ​​the tire.

[0003] Cables are said to be inextensible when said cables exhibit, under a tensile force equal to 10% of the breaking force, a relative elongation of at most equal to 0.2%.

[0004] Cables are said to be elastic when said cables exhibit, under a tensile force equal to the breaking load, a relative elongation of at least 3% with a maximum tangent modulus of less than 150 GPa.

[0005] The circumferential direction of the tire, or longitudinal direction, is the direction tangent to the periphery of the tire and defined by the rolling direction of the tire.

[0006] The axis of rotation of the tire is the axis around which it rotates in normal use.

[0007] A radial or meridian plane is a plane that contains the axis of rotation of the tire.

[0008] The circumferential median plane, or equatorial plane, is a plane perpendicular to the axis of rotation of the tire and which divides the tire into two halves.

[0009] The transverse or axial direction of the tire is parallel to the axis of rotation of the tire. An axial distance is measured along the axial direction. The expression "axially inside, respectively axially outside" means "whose axial distance measured from the equatorial plane is less than, respectively greater than".

[0010] The radial direction is a direction intersecting the axis of rotation of the tire and perpendicular to it. A radial distance is measured along the radial direction. The expression "radially inside, respectively radially outside" means "whose radial distance measured from the axis of rotation of the tire is less than, respectively greater than".

[0011] Radially outside the top reinforcement, there is the tread usually made of polymeric materials intended to come into contact with the ground in the contact area between the ground and the tire.

[0012] It is known to provide the tread, that is, the part of the tire intended to come into contact with the ground during rolling and to wear down during rolling, with a tread pattern formed of raised elements delimited by cutouts such as grooves, whether circumferential, transverse, or oblique. The objective of such a tread pattern is to give the tread good rolling performance on dry pavement and on water-covered pavement, particularly in wet weather.

[0013] To improve tread performance without excessively reducing the shear stiffness of said treads, it is known to form a plurality of transversely or obliquely oriented edges on the tread surface in order to cut the water film on a road surface and ensure good contact between the tread and the road. One means of obtaining such edges consists of providing the tread with a plurality of cutouts, these cutouts having the form of grooves or incisions. In the present application, incisions are distinguished from grooves in that the incisions have a width suitable for allowing at least partial contact between the opposing walls delimiting these incisions during rolling, particularly during contact with the ground, which would not be the case for grooves under normal tire operating conditions.

[0014] For the purposes of the invention, a longitudinally oriented cutout is a cutout in which the mean plane of at least a portion of the walls of said cutout forms an angle of less than 10° with a longitudinal plane. This angle formed with a longitudinal plane may be oriented in either direction with respect to said plane. longitudinal. A cut with a longitudinal orientation can also be a cut whose walls undulate or zigzag around a mean plane such as has just been described.

[0015] For the purposes of this invention, a transversely oriented cutout is a cutout in which the mean plane of at least a portion of the walls of said cutout forms an angle of less than 35° with a radial plane. This angle formed with a radial plane may be oriented in either direction with respect to said radial plane. A transversely oriented cutout may also be a cutout in which the walls undulate or zigzag around a mean plane such as the one just described.

[0016] For the purposes of this invention, an obliquely oriented cutout is a cutout in which the mean plane of at least a portion of the walls of said cutout forms an angle with a radial plane of between 35° and 80°. This angle formed with a radial plane may be oriented in either direction with respect to said radial plane. An obliquely oriented cutout may also be a cutout in which the walls undulate or zigzag around a mean plane such as has just been described.

[0017] Combined with this need to improve grip performance through the presence of edges formed by the transverse cuts, it is also required that the performance of a tread be consistent, that is to say, that satisfactory performance be achieved even after partial wear, to a greater or lesser degree. Partial wear of a tread is understood to mean a state of wear corresponding to a tread thickness no greater than the total tread thickness that can be worn before the tire needs to be changed, particularly for regulatory reasons.

[0018] The grooves generally include wear indicators, small platforms of vulcanized rubber compound covering a certain circumferential length of the bottom of these grooves. This indicator shows the minimum tread depth that must legally remain on the tread during use. Some tread patterns for heavy-duty vehicles are regroovable (an operation by which new grooves can be cut), and tires with such tread patterns bear the English word "Regroovable" or the symbol "U" on their sidewalls. Regrooving allows, on the one hand, for an extension of the grip potential of the heavy-duty tire and, on the other hand, for a significant increase in mileage.

[0019] Regrooving heavy goods vehicle tires is a common and authorized operation due to its safety benefits and increased efficiency. For example, it is explicitly authorized by the French Highway Code (Article 4 of the decree of October 24, 1994) and recommended by ETRTO and AFNOR (standard NFR12714). For this operation, manufacturers are required to provide regrooving diagrams that are mandatory for the technicians responsible for this regrooving.

[0020] The groove heights on new tires are measurable and the groove heights after regrooving can be deduced from these regrooving diagrams.

[0021] As is known per se, recutting a groove can be carried out using a heated, rounded blade, often still operated manually. This blade, attached to a frame that rests on the tread surface, can be used manually to follow the groove's path quite closely on the tread surface, even in the case of a groove with a non-straight path.

[0022] Regrooving restores sharp edges and is usually intended to restore a tread depth corresponding to that of a half-worn heavy-duty tire. Standard recommendations aim for a post-regrooving depth of 5 to 6 mm, consisting of 3 to 4 mm of regrooving and 2 mm of remaining depth; in practice, regrooving is often carried out earlier, with remaining depths of between 4 and 5 mm, resulting in a post-regrooving depth of 7 to 9 mm, for tire tread depths when new of between 12 and 20 mm.

[0023] Regrooving a tire has several advantages. First, by restoring the tread depth to the tire, regrooving extends the tire's life.

[0024] Furthermore, since regrooving is carried out when the tread thickness is at its lowest and therefore when the tire has the lowest rolling resistance, the distance traveled is extended when the rolling resistance is lowest.

[0025] Document WO 2022 / 180325 further proposes tires which can be regrooved at least once, whose tread depth in new condition is very low to allow for rolling that optimizes performance in terms of rolling resistance of the tire throughout its use.

[0026] However, regrooving can be considered a step in the life of the tire which penalizes its use because it is necessary to immobilize the vehicle and therefore potentially disrupt its performance.

[0027] The inventors have set themselves the task of being able to provide tires with the advantages of regroovable tires, that is to say, whose rolling distance can be increased after at least a first phase of wear and which retain good grip properties on wet ground throughout their uses.

[0028] This objective has been achieved according to the invention by a tire comprising a crown reinforcement, itself radially capped by a tread, made of at least one elastomeric compound, joined to two beads by means of two sidewalls, said tread comprising at least one through groove, forming at least one tread element constituting the tread of the tire, having a height HN3 between the bottom of said at least one through groove and the tread surface, when the tire is new, said tread comprising at least one non-through groove, forming a cavity delimited by a radially inner surface, a radially outer surface and two lateral walls connecting the radially inner and outer surfaces, and having a height HN4 between the radially inner surface and the radially outer surface, when the tire is new, the radially inner and outer surfaces and the two walls being formed by said at least one elastomeric compound constituting the tread,said at least one non-through groove being filled with a material capable of being fully released during tread wear down to said radially outer surface of said at least one non-through groove, and the radially outer surface of said at least one non-through groove being radially outer to the bottom of said at least one through groove, when the tire is new.

[0029] For the purposes of the invention, a through groove is a groove having an opening on the surface of the tread, when the tire is new, and forming at least one tread element constituting the tread of the tire.

[0030] For the purposes of the invention, a non-through groove is a cavity within the tread not visible when the tire is new.

[0031] In the context of the invention, the height of a through groove is measured in a meridional cross-section of the tire and corresponds to the distance measured between the radially outer surface of the tread, forming the contact area with the ground and extrapolated to disregard any cutouts, and the surface of the bottom of a through groove, said distance being measured in a direction normal to the radially outer surface of the tread. The bottoms of through grooves are the radially innermost points of said through grooves, disregarding the presence of elements such as wear indicators, regrooving depth indicator wells, or any other element whose sum of areas is less than 15% of the total area of ​​the cutout.

[0032] In the meaning of the invention, the height of a non-through groove is measured in a meridian section of the tire and corresponds to the distance measured between the radially inner surface and the radially outer surface of said non-through groove, when the tire is new, said distance being measured in a direction normal to the radially outer surface of the tread.

[0033] For the purposes of the invention, a material capable of being completely released during tread wear is a material that is not bonded to said material with at least one elastomeric compound constituting the tread. For example of a powdery material trapped in the non-through groove before the tire's curing stage during its manufacture. As the tread wears and the radially outer surface of the non-through groove is abraded, the material is released and completely expelled, notably due to centrifugal force when the wheels rotate, in use on a vehicle.

[0034] An example of manufacturing such a tread consists of producing a semi-finished product in a mold designed to produce a flat strip. First, the elastomeric compound constituting the tread, the underside of which will form the tread surface on the new tire, is deposited. Grooves are then created on this strip with the desired dimensions of the blind grooves, and these are filled with a powdered material. Finally, the entire assembly is covered with the elastomeric compound constituting the tread to a thickness corresponding to that desired in the tire between the crown reinforcement and the radially inner surface of a blind groove forming its base. The semi-finished product thus prepared in the form of a flat strip is attached to the tire being manufactured before the latter is cured, during which the blind grooves are produced in the curing mold.It is still possible to proceed with the curing of the semi-finished product thus prepared for application to a tire using techniques known to those in the trade, particularly for retreading worn tires. According to this technique, it is therefore possible to apply the tread, which is in a semi-finished state, to a new carcass or to a tire carcass that has already been used and prepared for retreading.

[0035] For producing the tread as a semi-finished product, it is possible to use printing techniques, such as additive manufacturing or 3D printing, which allow the creation of a layer of an elastomeric material through successive steps of simultaneous deposition and curing. Such techniques are described, for example, in documents FR 3 067 281 A1 or WO 2013 / 086577. This type of manufacturing allows, in particular, the creation of through and blind grooves without requiring either a molding step for the through grooves or a step to form the blind grooves.

[0036] Examples of powdered materials include sand, flour, or any other similar material. The material is advantageously chosen so that it can be compacted to exhibit incompressibility and rigidity properties that do not unduly disrupt the tire's performance during use, particularly when new. It is also possible to provide blocks of material the size of blind grooves, prepared beforehand and, for example, packaged in envelopes into which a vacuum is created to provide the desired rigidity. The material is advantageously chosen to be non-polluting and, even more advantageously, to be compactable. It is biodegradable since it will be released during rolling. The same applies to the casing if you want pre-prepared and vacuum-sealed blocks.

[0037] Tests carried out with tires according to the invention have shown that during tread wear, abrasion of the radially outer surfaces of the non-through grooves effectively releases the material filling them and transforms the non-through grooves into through grooves. These new through grooves replace the through grooves present on the tire when new and recreate a tread pattern at this stage of wear, whereas the through grooves present on the tire when new gradually disappear due to tread wear. This emergence of a new tread pattern is similar, in terms of the volume of grooves present on the tread, to the result obtained by regrooving tires designed to be regrooved.In the same way as with regroovable tires, the new through grooves restore wet grip properties, until the tire is completely worn, essentially identical to those of the tire when new and during its first phase of wear leading to the progressive disappearance of the through grooves, present on the tire when new, and ending with the transformation of the non-through grooves into through grooves.

[0038] Preferably according to the invention, the distance, measured along the normal to the radially outer surface of the tread, when the tire is new, between the radially outer surface of said at least one non-through groove and the bottom of said at least one through groove is greater than or equal to 2 mm, when the tire is new.

[0039] According to this preferred embodiment of the invention, the transformation of non-through grooves into through grooves occurs before reaching the wear limit of the through grooves present on the tire in its new condition.

[0040] Preferably, the non-through grooves are designed to transform into through grooves simultaneously with the reaching of the wear limit of the through grooves.

[0041] According to an advantageous embodiment of the invention, the height HN4 of said at least one non-through groove is greater than or equal to 70% of the groove height HN3 of said at least one through groove of the tire in its new condition.

[0042] Advantageously, according to the invention, the height corresponding to the distance between the new running surface and the radially inner surface of at least one non-through groove is greater than or equal to 200%, and preferably greater than or equal to 250%, of the height HN3 between the bottom of said groove and the minus one through groove and the tread surface when the tire is new.

[0043] According to this advantageous variant of the invention, it has appeared, in particular in comparison with conventional regroovable tires, that the performance in terms of rolling resistance is improved, while maintaining similar wet grip properties and for substantially identical mileages until complete tire wear.

[0044] The inventors have been able to demonstrate that the combination of a tread thickness substantially identical to that of a more conventionally designed tire with groove heights when new that are reduced compared to those of more conventionally designed tires makes it possible to significantly increase performance in terms of rolling resistance.

[0045] Indeed, for tread thicknesses similar to those of more conventionally designed tires, the height of the non-through grooves, when the tire is new, being greater than 70% of the height of the through grooves, when the tire is new, means that the height of the through grooves, when the tire is new, is reduced compared to that of more conventionally designed tires.

[0046] As stated previously, the regrooving of more conventionally designed tires results in groove heights less than half the groove height when new. According to this advantageous embodiment of the invention, for a given tread thickness, the transformation of non-through grooves into through grooves is likely to occur more quickly than the need for regrooving would arise for a more conventionally designed regroovable tire, i.e., with less tread wear than in the case of a more conventionally designed regroovable tire.

[0047] According to the same principle, tires according to this advantageous embodiment of the invention can be designed with a tread when new that is thicker than that of conventional regroovable tires, resulting in rolling resistance performance substantially identical to that of said conventional regroovable tires, combined with significantly higher mileage. Furthermore, the tire according to the invention maintains satisfactory wet grip performance until the tire is completely worn. Indeed, on the one hand, the thicker tread provides more material to wear away and therefore a higher potential mileage. On the other hand, contrary to expectations of lower rolling resistance performance due to the elastomeric mass of the tread More importantly, the design of the tire according to this advantageous embodiment of the invention limits the deformations of the tread and makes it possible to obtain performance in terms of rolling resistance substantially equivalent to that of said regroovable tires of more conventional design.

[0048] According to a first embodiment of the invention, said at least one through groove and said at least one non-through groove are circumferential.

[0049] According to a second embodiment of the invention, said at least one through groove and said at least one non-through groove are transverse.

[0050] According to a third embodiment of the invention, said at least one through groove and said at least one non-through groove are oblique.

[0051] According to other embodiments of the invention, the tire has a combination of through grooves and circumferential and / or transverse and / or oblique non-through grooves.

[0052] According to an advantageous embodiment of the invention, after regrooving, the height HN4 of said at least one non-through groove is greater than or equal to 85% of the groove height HN3 of said at least one through groove of the tire in the new condition and preferably even greater than 95% of the groove height HN3 of said at least one through groove of the tire in the new condition.

[0053] Either of the embodiments of the invention presented above can also be associated with the production of a complex tread, for example made up of at least two layers of radially superimposed elastomeric mixtures.

[0054] According to one embodiment of the invention, the crown reinforcement of the tire is formed of at least two working crown layers of inextensible reinforcing elements, crossed from one layer to the other making angles with the circumferential direction between 10° and 45°.

[0055] According to other embodiments of the invention, the top reinforcement also comprises at least one layer of circumferential reinforcing elements.

[0056] One embodiment of the invention further provides that the top reinforcement is completed radially on the outside by at least one additional layer, called a protective layer, of reinforcing elements called elastic, oriented with respect to the circumferential direction with an angle between 10° and 45° and in the same direction as the angle formed by the inextensible elements of the working layer which is radially adjacent to it.

[0057] According to any one of the embodiments of the invention mentioned above, the top reinforcement can be further supplemented, radially inside between the frame reinforcement and the radially inner working layer closest to said frame reinforcement, by a triangulation layer of inextensible metallic steel reinforcing elements making, with the circumferential direction, an angle greater than 60° and in the same direction as that of the angle formed by the reinforcing elements of the layer radially closest to the frame reinforcement.

[0058] Other advantageous details and features of the invention will become apparent from the description of exemplary embodiments of the invention with reference to Figures 1 and 2, which represent: - [Fig. 1], a meridian view of a diagram of a tire tread according to an exemplary embodiment of the invention, - [Fig.2], a meridian view of a tread pattern diagram of [Fig.1] after partial tread wear.

[0059] Figures 1 and 2 are not shown to scale for ease of understanding. They represent schematic partial views of the tread (1) of a tire, the central part having been truncated for ease of reading.

[0060] Fig. 1 schematically illustrates part of a tread 1 of a new tire, having a tread surface 2 made up of the radially outer surface of the tread.

[0061] In [Fig. 1], the tread 1 is shown with two through grooves 3 and two non-through grooves 4. The through grooves 3 have a bottom 8. The non-through grooves 4 are defined by a radially inner surface 5, a radially outer surface 6 and two walls 7. These radially inner surface 5, radially outer surface 6 and the walls 7 are formed by the elastomeric compound constituting the tread 1.

[0062] The through grooves 3 have a height HN3 of 7.5 mm when the tire is new. The tread is designed to be usable until wear reaches a height of 2 mm, a value close to the generally permitted legal limit.

[0063] The non-through grooves 4 have a height HN4 equal to 9.5 mm. The non-through grooves 4 have been provided in the tread 1 so that the distance, measured along the normal to the radially outer surface of the tread, when the tire is new, between the radially outer surface 6 of a non-through groove 4 and the bottom 8 of a through groove 3 is equal to or slightly greater than 2 mm, when the tire is new.

[0064] The through grooves are filled with compacted dry sand 9 during the manufacture of the tread 1. The tread 1 was prefabricated before assembly of the tire and curing of the latter according to the techniques described above.

[0065] Figure 2 illustrates the same tread 1 after wear that has led to the wear limit corresponding to a height Hu3 equal to 2 mm. The tread then presents a running surface 21. When the wear limit of the through grooves 3 is reached, the radially outer surface 6 of the non-through groove 4 is eliminated and the non-through groove 4 is transformed into a through groove 4, the latter presenting radially outwards an opening at the level of the running surface 21 of the tread, at this stage of its wear.

[0066] During the abrasion of the radially outer surface 6 of a non-through groove 4, the compacted sand previously trapped is released and is evacuated under the effect of centrifugal force during the rolling of the vehicle.

[0067] The height HN4 of the non-through grooves when the tire is new 4 represents 127% of the height HN 3 of the through grooves in the new condition.

[0068] The height corresponding to the distance between the tread surface in its new condition and said radially inner surface 5 of a non-through groove 4 is equal to 15 mm. It represents 200% of the height HN3 between the bottom of said at least one through groove 3 and the tread surface when the tire is new.

[0069] Tests were carried out with tires of size 315 / 70R22.5.

[0070] Tires I according to the invention are made in accordance with the representation in Figures 1 and 2.

[0071] A regroovable reference tire of the same size is manufactured according to a configuration corresponding to typical regrooving designs. It includes a regrooving layer at the bottom of the grooves such that the groove height after regrooving is 5 mm and represents 42% of the groove height in its new condition, which is 12 mm. This height after regrooving of 5 mm corresponds to a regrooving depth of 3 mm when the remaining groove height is 2 mm, a value close to the generally permitted legal limit corresponding to the minimum height. The height before regrooving, corresponding to the distance between the tread surface in its new condition and the bottom of the grooves after regrooving, is 15 mm.

[0072] A regroovable reference R2 tire of the same dimensions manufactured according to the teachings of document WO 2022 / 180325. It has a regrooving layer at the bottom of the grooves such that the groove height after regrooving is 9.5 mm and represents 127% of the groove height in its new condition, itself equal to 7.5 mm. This height after regrooving of 7.5 mm corresponds to a regrooving of 7.5 mm when a remaining groove height of 2 mm is present, a value close to the generally permitted legal limit corresponding to the minimum height. The height before the regrooving and corresponding to the distance between the running surface in the new condition and the bottom of the grooves after regrooving is equal to 15 mm.

[0073] Wet grip measurements were carried out on each of the tires under identical driving conditions in accordance with ISO 15222. The results are entirely comparable for all tires. The results showed that at all stages of tire wear, the wet grip properties are maintained.

[0074] Furthermore, wear tests were carried out to show substantially identical performance with the tires I according to the invention and the reference tires RI and R2. Indeed, the volume of elastomeric materials constituting the tread, to be worn during the life of the tire according to the invention and those of the reference tires RI and R2 including the regrooving phase are substantially identical for the three tires, which leads to similar service lives.

[0075] Rolling resistance measurements were also carried out on each of the tires under identical driving conditions in accordance with Regulation No. 117 of the United Nations Economic Commission for Europe (UNECE).

[0076] The measurements showed substantially equivalent performance for the tire I according to the invention and the reference tire R2. The performance in terms of rolling resistance of the reference tire R2 was significantly lower.

[0077] These various results show that the tires according to the invention have the advantages of regroovable tires, that is to say, tires whose rolling distance can be increased after at least an initial wear phase while maintaining good grip on wet surfaces throughout their service life, without requiring the vehicle to be immobilized. Such vehicle immobilization is indeed necessary to perform tire regrooving, as mentioned previously.

[0078] In addition, such tires may have the same advantages as regroovable tires according to embodiments such as those described in document WO 2022 / 180325 with regard to rolling resistance properties, improved compared to regroovable tires according to more conventional designs.

Claims

Demands

1. A tire, comprising a crown reinforcement, itself radially capped by a tread (1), made of at least one elastomeric compound, joined to two beads by means of two sidewalls, said tread (1) having at least one through groove (3), forming at least one tread element constituting the tread of the tire, having a height (HN3) between the bottom of said at least one through groove (3) and the tread surface (2), when the tire is new, characterized in that, said tread (1) has at least one non-through groove (4), forming a cavity delimited by a radially inner surface (5), a radially outer surface (6) and two lateral walls (7) connecting the radially inner (5) and outer (6) surfaces and having a height (HN4) between the radially inner (5) and radially outer (6) surfaces,when the tire is new, in that the radially inner (5) and outer (6) surfaces and the two walls (7) are formed by said at least one elastomeric compound of the tread, in that said at least one non-through groove (4) is filled with a material (9) capable of being completely released upon wear of the tread (1) down to said radially outer surface (6) of said at least one non-through groove (4), and in that the radially outer surface (6) of said at least one non-through groove (4) is radially outer to the bottom (8) of said at least one through groove (3), when the tire is new.

2. Tire according to claim 1, characterized in that the distance, measured along the normal to the radially outer surface of the tread, when the tire is new, between the radially outer surface (6) of said at least one non-through groove (4) and the bottom (8) of said at least one through groove (3) is greater than or equal to 2 mm, when the tire is new.

3. Pneumatic according to claim 1 or 2, characterized in that the height (HN4) of said at least one non-through groove (4) is greater than or equal to 70% of the groove height (HN3) of said at least one through groove (3) of the tire in new condition.

4. Tire according to any one of claims 1 to 3, characterized in that the height corresponding to the distance between the tread surface (2) in the new condition and said radially inner surface (5) of said at least one non-through groove (4) is greater than or equal to 200% of the height (HN3) between the bottom (8) of said at least one through groove (3) and the tread surface (2) when the tire is new.

5. Pneumatic according to any one of claims 1 to 4, characterized in that said at least one through groove (3) and said at least one non-through groove (4) are circumferential.

6. Pneumatic according to any one of claims 1 to 5, characterized in that said at least one through groove (3) and said at least one non-through groove (4) are transverse.

7. Pneumatic according to any one of claims 1 to 6, characterized in that said at least one through groove (3) and said at least one non-through groove (4) are oblique.

8. Tire according to any one of the preceding claims, characterized in that said tread (1) comprises, at least locally, at least two layers of radially superimposed elastomeric mixtures in the tread (1).