Tread Rib and Rubber Composition for Wet-Grip Tires
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Solution Overview
Problem
Existing tires do not adequately address the issue of wet grip performance, despite efforts to improve it, such as using a tire rubber composition with conjugated diene-based rubber and silica.
Innovation Solution
A tire design featuring a tread portion with four circumferential main grooves, a crown rib, and middle ribs, utilizing a rubber composition with a copolymer resin containing cyclopentadiene as a monomer component, and a specific sea ratio and plasticizer content to enhance wet grip performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the sea ratio of the crown rib and middle ribs is increased to improve wet grip performance, then the ground-contact area is improved, but the flexibility and water removal capability deteriorate
Solution Approach 1:
The tread pattern is designed with different sea ratios for different regions: the crown rib has a small sea ratio (0-15%) to maintain ground-contact area for wet grip, while the circumferential main grooves are strategically positioned to provide water removal channels. This local differentiation allows each region to optimize its function - the crown rib provides traction while the grooves evacuate water, resolving the contradiction between ground-contact area and water removal capability
2Reliability
If conventional rubber compositions with silica and conjugated diene-based rubber are used to improve wet grip, then adhesion is improved, but overall wet grip performance remains insufficient
Solution Approach 1:
The invention uses a composite rubber composition combining conjugated diene-based rubber (for adhesion and wet grip) with silica filler (for reinforcement and flexibility). This composite material approach allows the tire to achieve both good adhesion properties from the rubber and enhanced mechanical properties from the silica, resolving the insufficiency of conventional single-material approaches and improving comprehensive wet grip performance
Data Source
Figure 1
AI summary
Provided is a tire having improved wet grip performance. The tire is a tire having a tread portion, wherein a tread surface of the tread portion has four circumferential main grooves, a crown rib demarcated by the circumferential main grooves, and a pair of middle ribs adjacent to the crown rib across the circumferential main grooves, a total sea ratio N (%) of the crown rib and the middle ribs is greater than 0 and less than 15, the tread portion is composed of a rubber composition including a rubber component, a filler, and a plasticizer, the plasticizer contains a copolymer resin including cyclopentadiene as a monomer component, and when a total amount of the plasticizer per 100 parts by mass of the rubber component in the rubber composition is denoted by P (parts by mass), N/P is less than 3.0.