Tire tread regrooving process

Abstract

The invention relates to a method for regrooving a tire tread (1), comprising: - measuring, for each of a plurality of measurement points (12) on a surface of a tread (2) distributed over a plurality of radial half-planes (20), an altitude of the measurement point (12) relative to a reference level independent of the tread (2); - determining, for each radial half-plane (20), a height curve from the altitudes of the measurement points (12) located in that radial half-plane (20), each height curve reflecting a height curvature relative to layers in the tire (1) in that radial half-plane (20); - determining, from the height curves, a rubber height map on a circumference of the tire (1); - regrooving the tire (1) by creating grooves whose depths conform to this map. Figure for the abstract: Figure 4

Description

Title of the invention: Method for regrooving a tire tread technical field

[0001] The invention belongs to the field of tires, and more specifically relates to a method of regrooving a tire tread. Technological background

[0002] A tire has a tread pattern consisting of a pattern of raised features in the rubber, such as grooves and peaks, which gives the tire desired properties, such as water evacuation or road grip. Tire use causes abrasion of the tread rubber, which gradually leads to erosion of the tread pattern. The peaks become less high and the grooves less deep. The tire properties conferred by the tread pattern are progressively altered until they are no longer satisfactory. To allow monitoring of the acceptable level of tire deterioration, wear indicators are present in depressions such as grooves, generally taking the form of localized raised areas at the bottom of the tread.The condition of the tire tread is considered unsatisfactory when the distance between the top of the tread and the wear indicator becomes too small.

[0003] A tire with excessively worn tread can no longer be used to power a vehicle. As a cost-saving measure, and in order to reuse the same tire, the practice of regrooving the tread pattern has been implemented. Indeed, even though part of the tread corresponding to the crests of the tread pattern has disappeared, the tread still retains sufficient thickness to create grooves that recreate a tread pattern, allowing the tire to regain properties suitable for reuse. Regrooving a tire is therefore an operation that consists of removing rubber from the existing tread block to restore tread depth, according to a given pattern that may replicate the previous pattern or differ from it.

[0004] This re-grooving operation is usually performed manually, using a re-grooving tool operated by an operator, as described, for example, in patent document EP 2 025 501 AL. The re-grooving tool comprises a support with a gripping portion by which the operator holds the tool in their hand. The support carries a U-shaped blade heated by the flow of an electric current. and protruding from a support surface of the support. The operator presses the grooving tool against the tire tread surface, driving the blade into the tread rubber until the support surface rests against the tire tread. By moving the tool with the support surface against the tread surface, the operator cuts a groove or channel into the tread rubber. The depth of the resulting grooves corresponds to the extent to which the blade protrudes from the support surface. A tread pattern is thus recreated on the tread.

[0005] Such manual regrooving is a tedious and physically demanding task. A regrooving machine has already been proposed for regrooving a profile with at least one groove in a tire tread, comprising a tire housing for holding a tire on a drive axle, which is coaxial with an axis of rotation of the tire, drive means for rotating a tire received by the tire housing around the axis of rotation during a cutting operation, a cutting device which includes a cutting head with a blade and a support device for pressing the cutting head during a cutting operation on the tread of the tire received by the tire housing, so that a blade is in the groove of the tread.

[0006] However, whether this regrooving is done manually or by such a machine, the grooving depth corresponds to the protrusion of the blade relative to a contact patch on the tire. This grooving depth is dictated by the desired tread depth, which is determined by the corresponding blade protrusion setting. There is, however, a risk that the grooving will be too deep, leaving insufficient rubber thickness between the bottom of the tread and the top plies. In particular, it frequently happens that rubber wear is not uniform across the tread, and a grooving depth setting acceptable for the majority of the tread surface may be too deep for the most worn areas of the tread.

[0007] If the thickness of the rubber protecting the crown plies is no longer sufficient, the integrity of the crown plies can no longer be guaranteed. The tire can no longer be used despite regrooving, and cannot even be retreaded. This results in a severe economic loss, since not only can the tire no longer be reused, but the regrooving operation was carried out unnecessarily. To avoid this pitfall, it is possible to choose to regroove only lightly worn tires with even wear, which excludes many tires that could have been regrooved, or to choose a shallow regrooving depth, which reduces the service life of the regrooved tires. Presentation of the invention

[0008] The invention aims to provide a regrooving process that allows for easy regrooving of a tread pattern on a tire tread while ensuring the preservation of a protective layer of a given thickness of rubber above the top plies of the tire, while allowing for regrooving of tires with pronounced and / or non-uniform wear.

[0009] To this end, the invention proposes a method for regrooving a tire tread, comprising the following steps:

[0010] - to measure, for each of a plurality of measurement points of a surface of a tire tread, an altitude of the measurement point relative to a reference level independent of the tire tread, the measurement points being distributed over a plurality of radial half-planes of the tire;

[0011] - determine, for each radial half-plane of the plurality of radial half-planes, a height curve in this radial half-plane from the altitudes of the measurement points located in this radial half-plane, each height curve reflecting a height curvature of rubber relative to plies in the tire in this radial half-plane;

[0012] - to determine, from the height curves, a height map of the rubber on a circumference of the tire;

[0013] - recutting the tire by making grooves of varying depths conforming to the rubber height mapping.

[0014] The invention is advantageously and optionally complemented by the following various features taken alone or according to any of their various technically possible combinations:

[0015] - The measurement points are arranged in hollows in the surface of the strip of bearing.

[0016] - Measurement points correspond to wear indicator peaks, to bottoms of sculpture, or to the bottoms of re-dug wells.

[0017] - The plurality of measurement points includes at least 2 measurement points per half- radial plane, and the plurality of radial half-planes comprises at least 6 radial half-planes.

[0018] - Each height curve of a radial half-plane is determined by approximation altitude of the measurement points of this radial half-plane.

[0019] - During re-grooving, the groove depths are chosen according to heights defined by the gum height mapping to guarantee the preservation of a protective layer of sheets of a given gum height.

[0020] - The grooves extend deep into the rubber down to the layer of protection of groundwater.

[0021] - The depths of the grooves vary on the circumference and / or on the width of the pneumatic.

[0022] - The regrooving of the grooves is carried out by a regrooving machine carrying a digging blade whose position relative to the tire axis is a function of the tread depth mapping.

[0023] - The altitude measurement of the measurement points is carried out by a contact probe.

[0024] - The altitudes of the measurement points are measured by a probe without contact, preferably by a two-dimensional laser profilometer or by a laser rangefinder. Presentation of the figures

[0025] Other features, objectives and advantages of the invention will become apparent from the detailed description below, which is purely illustrative and not limiting, and which should be read in conjunction with the accompanying drawings, given by way of non-limiting examples and on which: - Fig. 1 schematically shows an example of a cross-sectional view of the top of a tire with a worn tread; - Fig. 2 schematically shows an example of a re-grooving machine according to one possible embodiment of the invention; - [Fig.3] schematically shows the altitude measurement of a measurement point according to one possible embodiment of the invention; - [Fig.4] schematically shows an example of the distribution of measurement points of a tire according to a possible embodiment of the invention; - [Fig.5] schematically shows the regrooving of the tire tread according to one possible embodiment of the invention; - Fig. 6 shows an example of a cross-sectional view of the top of a tire with a recut tread pattern according to one possible embodiment of the invention.

[0026] Throughout the figures, similar elements bear identical references. Detailed description

[0027] In the accompanying figures, the various geometric orientations are defined in an XYZ coordinate system, defined by a longitudinal or circumferential direction X, tangent to the circumference of the tire along its direction of travel, a transverse or axial direction Y, parallel to the axis of rotation of the tire, and a radial direction Z, perpendicular to the axis of rotation of the tire. A radial plane is understood to be a plane containing the axis of rotation of the tire and extending along a radial direction Z and the transverse direction Y. A radial half-plane is understood to be a A plane delimited by the axis of rotation of the tire and extending in the transverse direction Y and a radial direction Z from the axis of rotation of the tire

[0028] . Figure 1 shows an example of a cross-sectional view in a radial plane of a tire crown 1. It comprises a tread 2, intended to come into contact with the ground, to which two sidewalls 3 are attached at its axial ends. Reinforcing plies 4, called crown plies, generally metallic, are present in the rubber radially beneath the tread 2, under a thickness of rubber designated as the rubber pad 6. The tread 3 has, on its outer surface opposite the axis of rotation in the radial direction Z and outside the rubber pad 6, a relief pattern comprising, in the radial direction Z, grooves 8 and crests 10.The hollows 8 correspond to grooves in the tread 2, while the peaks 10 form the parts of the tread 2 that come into contact with the ground.

[0029] The example in [Fig. 1] shows a tire 1 whose tread pattern has been worn by rolling. The use of a tire 1 results in progressive wear and material loss in the areas in contact with the rolling surface, typically the road. Due to the tread pattern, it is the crests 10 of the tread, i.e., the areas between the grooves 8, that wear down and progressively lose height. Conversely, the tread bases, i.e., the bottoms of the grooves 8, are not normally in contact with the rolling surface and therefore wear much less. The distance between the crests 10 and the bottoms of the grooves 8 is thus reduced, and the grooves 8 become shallower. It frequently happens that the wear is not uniform across the tire, and therefore that some areas of the tread 2 exhibit a more pronounced reduction in the depth of the grooves 8 compared to other areas. In the example of [Fig.[l], the tire 1 has undergone asymmetric conical wear, which is reflected in the figure by shallower depressions 8 on the right of the figure than on the left.

[0030] The method aims to recut the tread of the tire 1 to create grooves that allow the tread to regain depths 8 suitable for giving the tire 1 properties that enable its reuse. The method is implemented using a recutting machine 100, as in the example illustrated in [Fig. 2]. Such a recutting machine 100 comprises a rotating shaft 102 carrying the tire 1 along its axis of rotation extending in the transverse direction Y, and a tool holder 104 adapted to hold and move a measuring instrument and / or a recutting blade facing the tread 2 of the tire 1. The tool holder 104 is preferably aligned with the rotating shaft 102 in a radial direction Z, and is movable in the radial direction Z towards the rotating shaft 102, and is preferably movable in the transverse direction Y in order to move the instrument or blade in the width of the pneumatic 1. The rotating axis 102 carrying the pneumatic 1 is configured to drive the pneumatic 1 in rotation, and is preferably movable at least in the vertical radial direction Z.

[0031] The method comprises, for each of a plurality of measuring points 12 on a tread surface 2 of the tire 1, measuring the altitude of that measuring point 12 relative to a reference level independent of the tire. A measuring instrument 14 whose position is known can be used. Preferably, as in the example in [Fig. 3], the measuring instrument 14 performing the altitude measurement is a contact probe. Other measuring instruments 14 can be used, such as a non-contact probe, in particular an optical measuring instrument such as a laser rangefinder. Such a laser rangefinder is preferably positioned directly above the tread surface 2 to be measured, in particular along the radial direction Z.A measuring instrument 14 formed by a non-contact sensor can also be a profilometer, which allows the altitudes of the surface of the tread 2 of the tire 1 to be measured over its entire width along the transverse direction Y.

[0032] However, an optical measuring instrument such as a laser rangefinder is sensitive to the cleanliness of the tire, whereas a contact probe is comparatively less sensitive to this cleanliness. For example, a contact probe is brought close to the measuring point, and when a sensitive tip of the contact probe encounters an obstacle offering sufficient resistance, a contact signal is emitted by the contact probe. The contact probe can be configured not to react to the presence of dust, which would offer only low resistance, but rather to react to the high resistance offered by the rubber of the tire 1. Therefore, such a probe has the advantage of measuring the actual condition of the tread surface 2 of the tire 1 more precisely.

[0033] The position of the measuring instrument 14 is known, and it is with respect to this position that the reference level, independent of the tread 2 of the tire 1, is determined. For example, in the case of a contact probe, it is the relative displacement between the contact probe and the axle carrying the tire before contact that determines the altitude. Typically, the contact probe is moved along the radial direction Z until it makes contact with the tire 1 at the measuring point 12, and the amplitude of the displacement corresponds to the altitude of the measuring point 12. Alternatively, the axle carrying the tire 1 can be moved along the radial direction Z until it makes contact with the contact probe. The reference level is thus linked to the displacement of the measuring instrument 14 or the axle, and can, for example, be a starting level before the displacement. In the case of a measuring instrument 14 Optically, it is the position of the measuring instrument 14 that can determine the reference level.

[0034] By way of illustration, a contact measuring instrument 14 may initially be at a reference altitude and then be moved along the radial direction Z, towards the axis carrying the tire 1. When the contact measuring instrument 14 touches the surface of the tread 2 of the tire 1 at the measuring point 12, the measuring instrument 14 sends a signal that stops the movement and allows the amplitude of the displacement to be recorded as the altitude of the corresponding measuring point 12. The contact measuring instrument 14 is moved in the opposite direction to return to its initial position, and the relative position between the measuring instrument 14 and the axis of the tire 1 is changed so that the measuring instrument 14 faces another measuring point 12. For example, the measuring instrument 14 may be translated, the axis may be translated, or the axis may undergo a partial rotation of the tire 1.The measuring instrument 14 can then measure the altitude of this new measuring point 12.

[0035] As illustrated in [Fig. 4], the measuring points 12 whose altitude is measured are distributed over a plurality of radial half-planes 20 of the tire. The plurality of measuring points 12 comprises at least 2 measuring points per radial half-plane 20, and preferably at least 3 measuring points 12 per radial half-plane 20, and even more preferably at least 4 measuring points 12 per radial half-plane 20. Thus, at least 2 measuring points 12 are aligned in the transverse direction Y. The plurality of radial half-planes 20 comprises at least 6 radial half-planes 20, and preferably at least 8 radial half-planes 20, and even more preferably at least 10 radial half-planes 20. The radial half-planes 20 are angularly distributed, preferably regularly angularly distributed, around the axis of rotation 22 carrying the tire 1.Preferably, there is at least one radial half-plane 20 equipped with measuring points 12 in each angular range of 60° around the axis of rotation 22 carrying the tire 1, and preferably at least two radial half-planes 20 in each angular range of 60° around the axis of rotation 22 carrying the tire 1. In the example of [Fig.4], four measuring points 12 are present on each of twelve radial half-planes 20 angularly spaced 30° around the axis of rotation 22 carrying the tire 1, i.e. 48 measuring points.

[0036] According to one embodiment, the measuring instrument 14 is a two-dimensional laser profilometer, which "scans" the entire width of the tread surface 2 of the tire 1 along the Y direction. Preferably, only the elevations of specific measurement points 12—or points of interest—are retained. Such a measurement is repeated circumferentially along the X direction, by moving the profilometer and / or by rotating the tire around its axis of rotation.

[0037] The number of measurement points 12 can be significantly higher, for example when the measuring instrument 14 is a non-contact probe, preferably when the measuring instrument 14 is a two-dimensional laser profilometer.

[0038] The measuring points 12 are chosen to allow the determination of the height, relative to the reference level linked to the regrooving machine 100, of a protective rubber layer in the tire 1. The measuring points 12 are therefore chosen outside the wear zones of the tire 1, which are essentially the peaks 10 of the tread surface 2. Preferably, the measuring points 12 are arranged in depressions 8 of the tread surface 2, for example in existing grooves of the tread 2. In particular, measuring points 12 may correspond to the peaks of indicators or wear indicators arranged in the depressions 8 or to the bottoms of depressions 8. The tread wear indicators 2 are the small raised rubber blocks found at the bottom of the grooves of the tread 2, protruding 1 to 2 mm from the bottom of the groove.Since tire 1 must be changed as soon as its wear reaches these indicators, the wear indicators are not normally worn. A tread depth, i.e., a groove depth, can also be used as a measuring point 12. As the groove depth is lower than a wear indicator, it should not normally be worn.

[0039] Preferably, it is possible to use the bottoms of re-drilling wells as measurement points 12. The figures show an example of a pneumatic 1 equipped with such re-drilling points 18.

[0040] A regrooving well 18 is a cavity of a given depth extending below the groove bottoms to reach the surface of the protective layer 24 of the plies 4. The presence of regrooving wells 18 is provided for during the manufacture of the tire 1 in order to locate the surface of the protective layer 24 of plies 4 that is to be retained, without needing to know the internal structure of the tire 1. In the absence of these regrooving wells 18, it is necessary to know the internal structure of the tire 1, or to follow the manufacturer's recommendations which specify the regroovable height, in order to know the thickness of the rubber mat 6 above the plies 4, and thus deduce the thickness of rubber that can be regrooved without reaching the protective layer 24 of plies 4.For each type of tire 1 to be regrooved without a regrooving well 18, it is sufficient to obtain information concerning the internal structure of the tire 1, for example by cutting a tire 1 of this type. If it is determined that the chosen measuring points 12, for example wear indicators, are separated from the plies 4 by a thickness of rubber 5 mm, and if it is desired to retain a protective layer of rubber 2 mm thick above. of the layers 4, then the measured altitude of the measuring points 12 reflects the height, relative to the reference level, of the surface of the protective layer by means of a translation of 3 mm in the radial direction Z. In all cases, the positions of the measuring points 12 on the tread 2 of the tire 1 are known, for example by an angle of rotation of the tire around the axis of rotation 22 and by a coordinate along the transverse direction Y.

[0041] Once the altitudes of the measurement points 12 have been obtained, a height curve 30 is determined for each radial half-plane 20 of the plurality of radial half-planes 20. The example in [Fig.5] shows the positioning of such a height curve 30 with respect to the measurement points 12.

[0042] Each height curve 30 reflects a curvature of the rubber height in the tire 1 in the corresponding radial half-plane 20. Like the altitudes from which it is derived, the height curve 30 is expressed relative to a reference level independent of the tread 2 of the tire 1. A height curve 30 can correspond to the curve of a protective layer 24 of plies 4 of a given rubber height. For example, if it is desired to maintain a protective layer 24 with a rubber height of 2 mm above the plies, the height curve 30 can be located 2 mm above the plies 4.

[0043] In the advantageous case where the measuring points 12 are bottoms of regrooving wells 18, the height curve 30 can be derived directly from the elevations of the measuring points 12, since these elevations directly indicate the height of the rubber layer that is to be retained as a protective layer 24. Otherwise, the elevations of the measuring points 12 are used to deduce the heights of the rubber layer above the plies 4, based in particular on knowledge of the structure of the tire 1. For example, if the measuring points 12 are arranged on a tread bottom (hollow 8) and if it is known that for this tire 1 the protective layer 24 of the plies 4 is located at a given depth relative to the tread bottom, then the heights of the protective layer 24 will correspond to the elevations of the measuring points 12 translated by this given depth.The same would apply to wear indicators or any other type of measuring point 12 whose altitude would have to be modified by a known value to correspond to a height of the protective layer 24 of the layers 4.

[0044] Each height curve 30 of a radial half-plane 20 is determined by approximating the altitude of the measurement points 12 of this radial half-plane 20. As explained above, the altitude can be modified to take into account the known distance, in the radial half-plane 20, between the measurement point 12 and the protective layer 24 of the water tables 4 that it is desired to retain. The determination of the height curve 30 aims to estimate the height of the protective layer 24 of the water tables. between the measurement points 12. Typically, the approximation used can be an interpolation. However, in order to guarantee the preservation of a protective layer 24 of the plies 4 of a given rubber height, it is preferable to impose as a constraint that the height curve 30 must pass above the heights of the protective layer 24 of the plies at the measurement points 12, called measured heights.

[0045] For example, interpolation by a circular arc can be used, with a radius of curvature chosen to reflect a priori curvature of the tire 1. When the radial half-plane 20 includes more than two measurement points 12 allowing the determination of at least two measured heights, several arcs can be used, each determined from a subset of measured heights, and the height curve 30 between measurement points 12 can correspond to the section of the highest arc between these measurement points. For the axial extremities of the height curve 30, beyond the extremal measurement point, it can be chosen to extend the height curve 30 tangent to the height curve 30, for example by extending the highest arc, by linear interpolation from the last two measured heights, or by a straight extension of the height curve 30 in the axial direction Y.Other types of interpolation can be used, provided they allow for the definition of a 30-millimeter curve passing over each measured height. Preferably, however, to maximize the regrooving depth, the 30-millimeter curve should not define a height greater than a predetermined value at each measured height, preferably more than 3 mm at each measured height. For example, the predetermined value is defined by the tire type of tire 1 and is thus determined from a data table.

[0046] Once a height curve 30 is determined for each radial half-plane 20, a rubber height map is determined on a circumference of the tire 1, from the height curves 30 of different radial half-planes 20. The aim is to define a rubber height for the entire tread 2 of the tire 1, which reflects the surface area of ​​the protective layer 24 of plies 4 that is desired to be retained.

[0047] The mapping is typically determined by an interpolation of the height curves 30. The shape of the internal structure of the tire 1 in a projection onto a plane orthogonal to the transverse direction Y can be approximated as a circular shape; the interpolation can, in particular, be carried out by a circle or a plurality of arcs of circles, with the constraint that the tread heights of the mapping must be greater than or equal to the heights measured in the radial half-planes. 20, and preferably greater than or equal to the curves of height 30 for each radial half-plane 20.

[0048] Once the rubber height map is established, this map is taken into account to determine the depths of the grooves 40 of the regrooving. More precisely, the map is used to define the regrooving depths of the grooves 40. In other words, the depths of the grooves 40 conform to the rubber height map.

[0049] Regrooving is performed by a regrooving machine 100 carrying a regrooving blade 106 whose position relative to the tire axis is a function of the tread depth map. The tire 1 is rotated around the rotating axis 102 that carries it, and the regrooving blade 106, for example U-shaped, is positioned so that its end cuts the rubber on the surface of the tread 2. A groove 40 is then formed. If the regrooving blade 106 is held fixed, the groove 40 is circumferential around the tire 1. The regrooving blade 106 can also be moved during regrooving, particularly in the transverse direction Y, in order to create a groove 40 having a transverse component.To move from one groove 40 to the other, it is sufficient to raise the digging blade 106 in the radial direction Z, then to change the relative position between the tire 1 and the digging blade 106, for example by transverse translation of the tool holder 104 carrying the digging blade 106, by rotation of the digging blade 106, and / or by rotation of the tire 1, to make a new groove 40 on the surface of the tread 2.

[0050] The depth of such a groove 40 is derived from the relative position between the ripper blade 106 and the tread surface 2 of the tire 1, and more specifically is determined by the height of the ripper blade 106 along the radial direction Z. This height is defined for each ripper position on the tread surface 2 from the tread height map, and not as a function of the tread surface 2. Since the depth of the grooves 40 is not determined with reference to the tread surface 2 of the tire 1, the depths of the grooves 40 vary over the circumference and / or the width of the tire 1.

[0051] The height of the digging blade 106 along the radial direction Z is chosen so that at any point of digging, the end of the digging blade 106 does not penetrate the protective layer 24 of the layers 4 to a given height of rubber. The rubber height map precisely reflects this rubber height to be maintained at every point. Thus, at a point of digging, the corresponding height in the rubber height map can correspond to the height along the direction radial Z for the digging blade 106, and therefore to the positioning of the tool holder 104 in the radial Z direction.

[0052] The height of the ripper blade 106 along the radial direction Z is preferably chosen to maximize the depth of the grooves 40 on the surface of the tread 2, in order to maximize the life of the tread of the tire 1. Therefore, the grooves 40 preferably extend deep into the rubber, along the radial direction Z, down to the protective layer of the plies 24.

[0053] The example in [Fig. 5] shows the same recutting blade 106 at five different recutting points in a radial half-plane. It can be seen that the elevation of the recutting blade 106 in the radial direction Z varies depending on the recutting point. However, the elevation of the tip of the recutting blade 106 is chosen here so that at every recutting point it reaches a height curve 30 defined by the rubber height map defining the protective layer 24 of the layers 4 to be retained.

[0054] It can be seen in [Fig. 6], which shows a recut groove, that the grooves 40 do not all have the same depth relative to the peaks 10 of the tread surface 2, but that, on the other hand, the grooves 40 have the same depth relative to the layers 4, since it is relative to these layers that the height of the recutting blade 106 was defined. However, the protective layer 24 of layers 4 may not always have the same thickness above the layers 4, but may have a guaranteed thickness above the layers 4.

[0055] Once all the grooves 40 have been cut into the tire 1, the tire 1 can be removed from the regrooving machine 100, and can be mounted on a vehicle axle for use.

[0056] The invention is not limited to the embodiments and variants described and shown in the accompanying figures. Modifications remain possible, particularly with regard to the constitution of the various technical features or by substitution of technical equivalents, without departing from the scope of protection of the invention.

Claims

Demands

1. A method for regrooving a tire tread (1), comprising the following steps: - measuring, for each of a plurality of measurement points (12) of a surface of a tread (2) of the tire (1), an altitude of the measurement point (12) relative to a reference level independent of the tread (2) of the tire (1), the measurement points (12) being distributed over a plurality of radial half-planes (20) of the tire (1); - determining, for each radial half-plane (20) of the plurality of radial half-planes (20), a height curve (30) in this radial half-plane (20) from the altitudes of the measurement points (12) located in this radial half-plane (20), each height curve (30) reflecting a height curvature of rubber relative to plies (4) in the tire (1) in this radial half-plane (20);- determine, from the height curves (30), a rubber height map on a circumference of the tire (1); - recut the tire (1) by making grooves (40) whose depths conform to the rubber height map.

2. Method according to claim 1, wherein the measuring points (12) are arranged in hollows (8) of the surface of the tread (2).

3. Method according to claim 2, wherein measurement points (12) correspond to wear indicator peaks, sculpture bottoms, or re-drilling well bottoms (18).

4. A method according to any one of claims 1 to 3, wherein the plurality of measurement points (12) comprises at least 2 measurement points per radial half-plane (20), and the plurality of radial half-planes comprises at least 6 radial half-planes (20).

5. A method according to any one of claims 1 to 4, wherein each height curve (30) of a radial half-plane (20) is determined by altitude approximation of the measurement points (12) of this radial half-plane (20).

6. A method according to any one of claims 1 to 5, wherein, during regrooving, the depths of the grooves (40) are chosen according to heights defined by the height mapping of gum to guarantee the preservation of a protective layer (24) of layers of a given gum height.

7. Method according to claim 6, wherein the grooves (40) extend deep into the rubber down to the protective layer (24) of plies.

8. A method according to any one of claims 1 to 7, wherein the groove depths (40) vary over the circumference and / or over the width of the tire.

9. A method according to any one of claims 1 to 8, wherein the regrooving of the grooves (40) is carried out by a regrooving machine (100) carrying a regrooving blade (106) whose position relative to the axis of the tire (1) is a function of the rubber height mapping.

10. A method according to any one of claims 1 to 9, wherein the measurement of the altitudes of the measurement points (12) is carried out by a contact probe.

11. A method according to any one of claims 1 to 9, wherein the measurement of the altitudes of the measurement points (12) is carried out by a non-contact probe, preferably by a two-dimensional laser profilometer or by a laser rangefinder.

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