Studded tyre having grooves

A tyre comprising:

• a tread comprising tread blocks such that grooves are arranged between the tread blocks, and
• studs installed into at least some of the tread blocks, wherein:
• the tread blocks define:
• a land portion of the tread, the land portion comprising parts of the tread blocks and the studs arranged to contact a ground surface when the tire is in use, the land portion having a total land area, and
• an envelope surface comprising the land portion of the tread and regions defined by openings of the grooves, the envelope surface having a total envelope area, and
• an average land ratio of the tyre, the average land ratio being defined as a ratio of the total land area to total envelope area, is 55% to 78%;
• a central region of the tread is arranged between a first shoulder region of the tread and a second shoulder region of the tread, the central region comprising a circumferential central line of the tread, and
• the land portion of the tread comprises:
• a central land area being an area of a part of the land portion of the tread that belongs to the central region,
• a first shoulder land area being an area of a part of the land portion of the tread that belongs to the first shoulder region, and
• a second shoulder land area being an area of a part of the land portion of the tread that belongs to the second shoulder region, and
• the envelope surface comprises:
• a central envelope area being an area of the part of the envelope surface that belongs to the central region,
• a first shoulder envelope area being an area of a part of the envelope surface that belongs to the first shoulder region, and
• a second shoulder envelope area being an area of a part of the envelope surface that belongs to the second shoulder region,
• wherein a central land ratio of the tyre, the central land ratio being defined as a ratio of the central land area to the central envelope area, is 1 to 30 percentage points greater than either or both of:
• a first shoulder land ratio of the tyre, the first shoulder land ratio being defined as a ratio of the first shoulder land area to the first shoulder envelope area and
• a second shoulder land ratio of the tyre, the second shoulder land ratio being defined as a ratio of the second shoulder land area to the second shoulder envelope area,
• wherein:
• at least some of the tread blocks are provided with sipes,
• a width of all of the sipes is less than 1.2 mm,
• a depth of all of the sipes is at least 2.0 mm and at most equal to a depth of one of the grooves,
• at least a part of one of the studs is arranged in a stud hole provided in one of the tread blocks,
• no part of any of the sipes is arranged closer than 6 mm to a centre of the stud hole;
• at least some of the tread blocks of the central region are provided with sipes, such that the tyre has a first density of sipes, the first density of sipes being defined as a total length of the sipes arranged in the central region divided by the area of the central region,
• at least some of the tread blocks of the first shoulder region are provided with sipes, such that the tyre has a second density of sipes, the second density of sipes being defined as a total length of the sipes arranged in the first shoulder region divided by the area of the first shoulder region,
• at least some of the tread blocks of the second shoulder region are provided with sipes, such that the tyre has a third density of sipes, the third density of sipes being defined as a total length of the sipes arranged in the second shoulder region divided by the area of the second shoulder region, and
• the first density of sipes is at least 15% greater than at least one of:
• the second density of sipes and
• the third density of sipes;
• wherein the tyre comprises at least one ply, at least one metal belt, a cap layer forming at least part of a running surface of the tyre, an underlayer made of a first rubber compound, and an intermediate layer made of a second rubber compound, the intermediate layer being arranged, at least partially, between the underlayer and the cap layer,
• wherein the first rubber compound has a first Shore hardness (ShA) between 45 ShA and 65 ShA, the second rubber compound has a second Shore hardness (ShA) between 66 ShA and 80 ShA, and the tread comprises rubber material having a Shore hardness (ShA) of 48 ShA to 59 ShA,
• wherein at least a plurality of the studs comprise a body comprising a base flange and a second part, the second part comprises a second flange and a waist, the waist connecting the base flange to the second flange, the second part extending in a longitudinal direction of the stud from the base flange,
• wherein at least part of the base flange of the plurality of studs is surrounded by the underlayer and at least part of the second flange of the plurality of studs is surrounded by the cap layer, and
• wherein a dynamic stiffness of the underlayer is configured to be less than 25 MPa determined at 20° C., the dynamic stiffness of the underlayer determined at −25° C. is configured to be at least 20 times the dynamic stiffness of the underlayer determined at 20° C., and the dynamic stiffness is determined according to the standard ISO 4664-1:2011 in compression.