TISB Vol. 21 No. 4 Page 1 of 2

TIRE INFORMATION SERVICE BULLETIN

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The condition, sometimes referred to as sidewall undulations, is a common characteristic of radial tire construction. These indentations are more noticeable in tire sizes with higher aspect ratios and/or higher inflation pressures.In a radial tire the body ply cords run straight across the tire from bead to bead. The joining of the ply material creates a narrow overlap of ply cords in the radial direction at each junction. These overlapped ply cords slightly restrict the natural expansion of the sidewall when inflated. This results in an indentation. Since the belt plies reinforce the tread, only the sidewalls are indented.

SIDEWALL INDENTATIONS IN RADIAL TIRES

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Copyright © 2017 U.S. Tire Manufacturers Association TISB 21/4-0517

TISB Vol. 21 No. 4 Page 2 of 2

This Bulletin Replaces Volume 21, Number 3

Sidewall indentations are a cosmetic characteristic and will not affect the performance of the tire. If bulges, rather than indentations, appear on the sidewall or if there is any question concerning the sidewall appearance, the tire should be examined by a tire service professional.