It is an object to reduce tire vibration during high-speed travel on paved roads without lowering traction performance in fields. An agricultural machine tire includes: lug blocks disposed in a tread portion and formed alternately on both sides of a tire equatorial plane in a tire circumferential direction; and a central rib extending in the tire circumferential direction and to which end portions of the lug blocks on the tire equatorial plane side are integrally connected, and when a tire width length of the central rib from connecting portions to the tire equatorial plane is taken as a first rib width and a tire width length of the central rib from end edges of the central rib from the connecting portions across the tire equatorial plane to the tire equatorial plane is a second rib width, the width of the first rib is greater than the second rib.

A pneumatic tire adapted to effectively suppress temperature rise of a tread portion during loaded rolling of the tire, and sufficiently suppress failure of the tread portion due to the temperature rise. The tread portion of the pneumatic tire extends between both tread ends and has a tread surface with lug grooves. Each lug groove extends in a tire width direction and has an opening at its one end to a buttress that extends from the tread end radially inwards of the tire. The buttress has a surface with a projection on one side, in a tire circumferential direction, of the buttress-side opening of the lug groove to protrude in the tire width direction. The projection has a radially outer end in a radially outer side than a radially inner end of the buttress-side opening of the lug groove.

Tire for a vehicle for agricultural use comprises tread (2), comprising lugs (3) separated by grooves (4), each lug (3) extending radially outwards, over a radial height H, from a bottom surface (5) as far as a contact face (6). A first lug portion (31), made of a first elastomeric compound, extends radially inwards, from the contact face (6) as far as a first interface (7), over a radial distance D.sub.1 between 0.5 H (the radial height) and H. A second lug portion (32), made of a second elastomeric compound, extends radially inwards, from the first interface (7) as far as the bottom surface (5), over a radial distance D.sub.2. The second elastomeric compound extends radially into the lugs (3) and grooves (4), from the bottom surface (5), as far as a second interface (8), over a radial distance D.sub.3 between 3 mm and 15 mm.

The tread pattern of a tire for a vehicle for agricultural use comprises two rows of lugs (R1, R2), a first row being made up of a circumferential distribution of at least two families of lugs, over one revolution of the wheel; a first family is reproduced with a shortest spacing S, and a second family is reproduced with a longest spacing L; the tread pattern of the tread is designed such that the distance between the axially outer end of a following lug and the axially inner end at the centre of the tread is referred to as the overlap distance R. The ratio of the shortest spacing S of the family of lugs to the longest spacing L, S/L, lies in the range [0.6; 0.8]. The circumferential overlap distance R between the first and second circumferential rows of lugs is constant around the entire circumference of the tire.

A tire for an agricultural vehicle, having a tread consisting of blocks in pairs separated by voids and arranged, over the width of the tread, in a median row, two intermediate rows and two lateral rows. To obtain compromise between rolling resistance and service life in terms of wear in road use, two consecutive blocks of the median row) are separated by a transverse void with a width (E1) at most 2.5 mm, the mean circumferential slenderness ratio of every block) of the median row is at least 0.95 and at most 1.15, every block of each intermediate row has a leading face) in the circumferential rolling direction tire which forms a mean angle (D2) equal at least to 30 with a radial direction (ZZ) tire, and the mean circumferential slenderness ratio of every block in each lateral row is at most 0.9.

Tire with a tread provided with two edges (25A, 25B) and with a centre (C) dividing it into two parts of equal width with sets of blocks (21A, 21B). Each set of blocks (21A, 21B) has three zones: at the edge (211), at the centre (213) and intermediate (212). Each set of blocks (21A, 21B) has a set of chamfers (26A, 26B, 26C) which extends over at least the edge zone (211) and the central zone (213) of the set of blocks (21A, 21B). The width LC2 of the set of chamfers (26A, 26B, 26C) over the intermediate zone (212) is different from the width LC3 of the set of chamfers (26A, 26B, 26C) over the central zone (213), said widths LC2 and LC3 being comprised between 0.5 mm and 2.5 mm.