The glass beads suitable for use as tire balancing beads are specifically tempered glass beads with strict performance and structural requirements, tailored to withstand the harsh internal environment of tires (high-speed rotation, temperature fluctuations, friction) and ensure effective dynamic balancing. The key criteria are as follows:
- Material & Hardness: They must be made of high-purity tempered glass (typically with a silica content of over 70%). Tempering treatment enhances their hardness (Mohs hardness 6–7) and impact resistance, preventing breakage or pulverization during high-speed tire rotation (which would cause debris to clog the valve stem or scratch the tire inner wall).
- Sphericity & Uniformity: High sphericity is critical—ideally, the beads should be near-perfect spheres with minimal irregularities. This ensures they can roll and distribute evenly inside the tire under centrifugal force, avoiding agglomeration and ensuring consistent balancing effects. Additionally, the particle size must be uniform (common ranges: 1–2 mm for passenger car tires, 2.5–3 mm for heavy-duty truck tires); inconsistent sizes can disrupt weight distribution.
- Surface Treatment: Most qualified tire balancing glass beads undergo a silicone coating or anti-adhesion treatment. This coating prevents the beads from clumping due to moisture (condensation inside tires from temperature changes) or static electricity, maintaining their free-flowing ability to adapt to real-time tire imbalance.
- Density: The optimal density is around 2.4–2.6 g/cm³. A density that is too low (e.g., plastic beads) will fail to be propelled effectively by centrifugal force, while overly high density (e.g., metal beads) adds unnecessary load to the tire and increases wear on the inner wall.
- Chemical Stability: They must be chemically inert, resistant to corrosion from tire rubber additives, oil residues, or moisture. This ensures the beads do not degrade (e.g., discolor, soften) over long-term use (typically 3–5 years), maintaining their structural integrity and balancing performance.
- Compatibility: They must be compatible with tire pressure monitoring systems (TPMS). The beads should not interfere with TPMS sensor signals or damage sensor components, and should not violate tire manufacturers’ warranty terms (e.g., avoiding beads that leave abrasive residues).
In summary, only tempered glass beads meeting the above standards—with high hardness, excellent sphericity, anti-clumping surface treatment, and appropriate density—can function reliably as tire balancing beads to achieve long-term, dynamic tire balancing.