Tire Sidewall Hardness Gradient for Cornering Stiffness
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Solution Overview
Problem
Two-wheeled automotive vehicle tires face challenges in providing both excellent stiffness feeling and ground-contact feeling during cornering, as increased stiffness impairs ground-contact feeling, while insufficient stiffness reduces reaction force.
Innovation Solution
A tire design featuring a sidewall with a harder first layer outward of the bead and a softer second layer radially extending from the first layer, where the second layer's softer nature allows for flexible deformation, enhancing ground-contact feeling, and the harder first layer contributes to stiffness and reaction force, with specific hardness and elastic modulus ratios optimizing these properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the stiffness of the side portion is increased, then reaction force in cornering is improved, but ground-contact feeling is impaired
Solution Approach 1:
The sidewall is divided into two layers with different hardness: a harder first layer (H1) axially outward of the bead for stiffness, and a softer second layer (H2) radially outward from the first layer for ground-contact feeling. The hardness ratio H2/H1 is controlled at 0.70-0.95, creating local quality differentiation that resolves the contradiction between side portion stiffness and ground-contact feeling.
2Ease of operation
If the stiffness of the side portion is insufficient, then ground-contact feeling is improved, but reaction force in cornering is reduced
Solution Approach 1:
The first layer with higher hardness H1 is positioned axially outward of the bead to provide sufficient side portion stiffness for cornering reaction force, while the second layer with lower hardness H2 is positioned radially outward to provide ground-contact feeling. This local quality differentiation ensures both stiffness and operability are achieved in their respective locations.
Data Source
AI summary
In a tire 2, each of sidewalls 6 includes a first layer 36 disposed axially outward of a corresponding one of beads 8, and a second layer 38 extending outward from the first layer 36 in a radial direction. When Pc represents a position of an axially outer end of an interface between a carcass 10 and the sidewall 6, an outer end 40 of the first layer 36 is disposed radially inward of the position Pc. A hardness H1 of the first layer 36 is greater than a hardness H2 of the second layer 38. A ratio (H2/H1) of the hardness H2 to the hardness H1 is preferably not less than 0.70 and preferably not greater than 0.95.