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Pneumatic radial tire for heavy loads

  • US 5,833,780 A
  • Filed: 06/06/1996
  • Issued: 11/10/1998
  • Est. Priority Date: 06/21/1995
  • Status: Expired due to Term
First Claim
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1. A pneumatic radial tire for heavy loads, wherein a belt layer comprising a plurality of plies is arranged in a part of a tread portion which is on an outer circumference of a carcass layer, a plurality of main grooves extending in the circumferential direction of said tire being provided in an outer surface of said tread portion so as to form a plurality of tread elements separated by said main grooves, the tread elements including axially outermost tread elements and second inner tread elements,shoulder side edge portions of at least the second inner tread elements counted from the axially outermost tread elements of said tread portion being provided with narrow grooves extending in the circumferential direction of said tire and having depthwise axes inclining from said tread surface toward a tread center, so as to divide said second inner tread elements into narrow ribs of an unchanged height and tread elements adjacent to said narrow ribs, a ratio W2 /W1 of a width W2 of each of said narrow ribs to a width W1 of each of said tread elements adjacent to said narrow ribs being set in the range:

  • 
    
    space="preserve" listing-type="equation">0.1 ≦

    W.sub.2 /W.sub.1 ≦

    0.5,edge portions of said narrow ribs being chamfered,an angle of inclination α

    of the depthwise axis of each of said narrow grooves with respect to the normal of said tread surface, and an angle of inclination β

    of each of main groove side walls, which face the tread center, of said tread elements adjacent to said narrow ribs with respect to the normal of said tread surface being set so that they have the relation of 0<

    α

    <

    β

    , and the relation between said angles α

    , β and

    an angle of inclination θ

    of a tread surface of each of said tread elements adjacent to said narrow ribs with respect to the axis of said tire being such that;

    
    
    space="preserve" listing-type="equation">3.4θ







    )/2≦

    6.4θ

    .

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