Precured Tread with Localized Rubber Hardness for Retreaded Tire Attachability
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Solution Overview
Problem
The existing retreaded tires face issues with attachability and durability due to the limited curvature radius of the buffed shoulder portion, leading to inferior appearance and abrasion resistance, especially when using a precured tread with a narrower width than the base tire, and the cap and base structure's abrasion resistance imbalance.
Innovation Solution
A precured tread with different types of tread rubbers are disposed in the central and side regions, where the side regions have softer rubber to accommodate smaller buff R, and a base rubber layer with lower heat generation properties is used, extending across 80-95% of the attaching surface width to improve attachability and maintain adhesion and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If a precured tread with the same tread width as a new tire is attached to a base tire with small buff R, then the tread width is sufficient, but the end portion cannot be smoothly curved and attachability is low
Solution Approach 1:
The precured tread is divided into multiple regions (central region and side regions) with different rubber compositions and properties. The side regions use softer rubber to accommodate the small buff R and achieve smooth curvature, while the central region uses harder rubber for abrasion resistance. This segmentation allows each region to be optimized for its specific function.
Solution Approach 2:
Different types of tread rubbers are disposed in different regions of the precured tread. The side regions have softer rubber with lower hardness to facilitate curving along the small buff R, while the central region has harder rubber for wear resistance. This local differentiation of material properties resolves the contradiction between maintainin gfull tread width and achieving proper attachability.
2Manufacturing precision
If a precured tread with narrower tread width is attached to a base tire with small buff R, then attachability is improved, but appearance and abrasion resistance are inferior
Solution Approach 1:
The precured tread is segmented into central and side regions with different rubber formulations. The side regions use softer rubber optimized for attachability to base tires with small buff R, while the central region uses harder rubber optimized for abrasion resistance. This segmentation allows the tread to achieve both good attachability and adequate abrasion resistance without narrowing the overall tread width.
3Strength
If hard rubber is used in the precured tread for abrasion resistance, then abrasion resistance is improved, but the end portion is difficult to curve along small buff R
Solution Approach 1:
The precured tread employs local quality differentiation by using softer rubber in the side regions where curvability is needed to match the small buff R, while using harder rubber in the central region where abrasion resistance is critical. This localized material property optimization allows the tread to achieve both good curvability for attachment and adequate abrasion resistance.
4Strength
If the cap rubber layer covers the base rubber layer across the entire width, then abrasion resistance is improved, but the end portions are difficult to attach to base tire with small buff R
Solution Approach 1:
The precured tread is segmented into central and side regions with different rubber compositions. The side regions use softer rubber that can be smoothly curved along the small buff R of base tires, while the central region uses harder rubber for abrasion resistance. This segmentation resolves the contradiction between maintaining full-width cap layer coverage for abrasion resistance and achieving proper attachability at the ends.
Data Source
AI summary
The object is to provide a precured tread for a retreaded tire improving attachability to a base tire. In a strip-shaped precured tread 10 to be attached to a crown portion of a base tire 32 from which a tread has been removed, side tread rubbers 14 disposed in side regions CS on both sides of a central region CN are set to have JIS A hardness lower than that of a central tread rubber 12 disposed in the central region CN including a widthwise centerline C so as to improve attachability to a base tire.