Pneumatic bias tire

Abstract

There is provided a pneumatic bias tire capable of preventing a separation failure between carcass plies in the bending deformation of a tire side portion under an action of a high load. In a heavy duty pneumatic bias tire having a ply rating of not less than 58 and an aspect ratio of not more than 80%, a rubber volume as the product of a distance between ply cords in the carcass ply and a distance between ply cords of mutually adjoining carcass plies with respect to three or more inside carcass plies of an innermost carcass ply group in at least a portion corresponding to a position of a maximum tire width is 500-1350 mm 3 .

1 . A pneumatic bias tire comprising plural pairs of bead cores and plural carcass ply groups corresponding to the number of bead core pairs, carcass plies of ply cords coated with a coating rubber constituting each group being wound around each bead core, and having a ply rating of not less than 58 and an aspect ratio of not more than 80%, in which a rubber volume as a sum of the product of a distance between ply cords in the carcass ply and a distance between ply cords of mutually adjoining carcass plies per unit area of 50 mm square and a depth size with respect to three or more inside carcass plies of an innermost carcass ply group in at least a portion corresponding to a position of a maximum tire width is 500-1350 mm 3 .  
   
   
       2 . A pneumatic bias tire according to  claim 1 , wherein a peel strength index represented by the following equation among at least three inside carcass plies in the innermost carcass ply group is made 1.3 times or more than that among the carcass plies in the other carcass ply groups.  
         F =6.8×(50 /N−D )+3.6 ×T +9.7  
     wherein N: number of ply cords per 50 mm 
 D: diameter of ply cord (mm)  
 T: rubber gauge between ply cords of adjoining carcass plies.  
 
   
   
       3 . A pneumatic bias tire according to  claim 1  or  2 , wherein said tire satisfies requirements of Ni=30-40 (cords), No=50-60 (cords), Ni/No=0.6-0.8 and Ti/Di=1.6-2.2, To/Do=0.6-1.0, (Ti/Di)/(To/Do)=1.9-3.55 when an average end count in at least three inside carcass plies of the innermost carcass ply group is Ni, a rubber gauge between the ply cords of the adjoining carcass plies is Ti (mm), a diameter of the ply cord is Di (mm), an average end count in the carcass plies of the other carcass ply groups is No, a rubber gauge of the ply cords of the adjoining carcass plies is To (mm) and a diameter of the ply cord is Do (mm).