Motorcycle Tyre Bead Geometry for Rim-Slip Resistance
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Solution Overview
Problem
Existing motorcycle tires face a trade-off between improving rim-slip resistance performance and maintaining rim-mountability performance, where enhancing rim-slip resistance often leads to a deterioration in steering stability.
Innovation Solution
The design includes a pair of bead portions with specific geometric configurations, such as bead bottom and side surfaces, where the diameter of the intersection of virtual straight lines is between 99.0% to 99.6% of the standard wheel rim diameter, optimizing the angles of these surfaces to enhance rim-slip resistance while maintaining rim-mountability and steering stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the bead portion geometry is modified to improve rim-slip resistance, then steering stability improves, but rim-mountability deteriorates
Solution Approach 1:
The invention modifies the geometric parameters of the bead portion, specifically defining the bead bottom surface angle α and bead side surface angle β with precise mathematical relationships to the rim diameter. By changing these angular parameters within specific ranges, the invention achieves improved rim-slip resistance while maintaining rim-mountability, resolving the technical contradiction between these two performance aspects.
Solution Approach 2:
The invention applies different surface characteristics to different parts of the bead portion. The bead bottom surface has a specific angle range (0° < α ≤ 15°) optimized for rim contact and slip resistance, while the bead side surface has a different angle range (45° ≤ β < 90°) optimized for mounting. This local differentiation of surface properties allows simultaneous optimization of both rim-slip resistance and rim-mountability.
2Reliability
If the bead bottom surface angle is increased to improve rim-slip resistance, then steering stability improves, but the tyre becomes harder to mount on the rim
Solution Approach 1:
The invention establishes a specific parameter range for the bead bottom surface angle (0° < α ≤ 15°) that balances steering stability with mounting ease. By constraining α to this range and defining its relationship with the bead side surface angle β through the formula tan(α) × tan(β) = 0.1 to 0.3, the invention achieves optimal steering stability without excessive mounting difficulty.
Solution Approach 2:
The invention uses a moderate bead bottom surface angle (not maximizing it completely) to achieve sufficient rim-slip resistance while avoiding excessive mounting difficulty. This partial action approach finds the optimal balance point rather than pushing the parameter to its extreme, resolving the contradiction between steering stability and mounting ease.
Data Source
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AI summary
A motorcycle tyre includes a pair of bead portions each with a bead core therein, the pair of bead portions including a pair of rim contact surfaces that comes into contact with a standard wheel rim under a standard-rim mounted condition. Each rim contact surface includes a bead bottom surface, a bead side surface, and a bead heel surface connecting the bead bottom surface and the bead side surface. Under a virtual-rim mounted condition, in at least one of the pair of bead portions, a diameter of an intersection of a virtual first straight line expanded outwardly in the tyre axial direction from the bead bottom surface and a virtual second straight line expanded inwardly in the radial direction from the bead side surface is 99.0% to 99.6% of a rim diameter of the standard wheel rim.