Tread for heavy vehicle tire

A tread for a heavy vehicle tire, said tread having:

• a total width W and being provided with two main grooves of circumferential overall orientation,
• said main grooves dividing said tread into three regions including a middle region (M) and two edge regions (B) axially on each side of said middle region,
• said middle region (M) having an axial width Lm at least equal to 45% and at most 70% of the total width W of said tread,
• said tread having a total void volume V0 when new,
• said middle region of this tread having a total void volume Vm when new,
• a volume void ratio being calculated as a ratio between said total void volume V0 and a total volume including all voids and evaluated between said tread surface when new and an internal surface extending in said tread parallel to said tread surface when new,
• said volume void ratio of said tread when new being less than 17%
• said internal surface being in contact radially on an inside with innermost points of deepest ones of said main grooves,
• said middle region comprising a plurality of transverse or oblique sipes having a depth at least equal to 75% of the depth of said main grooves,
• said transverse or oblique sipes opening into said main grooves delimiting said middle region (M) and being formed at a mean spacing Pm,
• wherein said middle region has a volume void ratio when new less than half said total volume void ratio of said tread when new and wherein at least one continuous circumferential channel is formed under said tread surface when new so that it appears when said tread becomes part worn and forms a new groove, and
• wherein said edge regions are provided with transversely or obliquely oriented sipes arranged at a mean spacing Ps, said mean spacing Ps being greater than said mean spacing Pm of said sipes in said middle region.

A tread for a heavy vehicle tire, said tread having:

• a total width W and being provided with two main grooves of circumferential overall orientation,
• said main grooves dividing said tread into three regions including a middle region (M) and two edge regions (B) axially on each side of said middle region,
• said middle region (M) having an axial width Lm at least equal to 45% and at most 70% of the total width W of said tread,
• said tread having a total void volume V0 when new,
• said middle region of this tread having a total void volume Vm when new,
• a volume void ratio being calculated as a ratio between said total void volume V0 and a total volume including all voids and evaluated between said tread surface when new and an internal surface extending in said tread parallel to said tread surface when new,
• said volume void ratio of said tread when new being less than 17%,
• said internal surface being in contact radially on an inside with innermost points of deepest ones of said main grooves,
• said middle region comprising a plurality of transverse or oblique sipes having a depth at least equal to 75% of the depth of said main grooves,
• said transverse or oblique sipes opening into said main grooves delimiting said middle region (M) and being formed at a mean spacing Pm,
• wherein said middle region has a volume void ratio when new less than half said total volume void ratio of said tread when new and wherein at least one continuous circumferential channel is formed under said tread surface when new so that it appears when said tread becomes part worn and forms a new groove, and
• wherein said volume void ratio of said tread when new is less than 10% and wherein said volume void ratio of said middle region when new is at most equal to 3%.