How Schrader TPMS Solutions Measure Up
Every Schrader TPMS sensor is thoroughly in-process tested across an array of dimensional, visual and operational conditions. Each of the fundamental components falls under this rigorous testing, including:
- The sensor enclosure with potting secures and holds the printed circuit board (PCB) and all components within the sensor, across all environments
- The pressure transducer executes the measurement of tire pressure within each tire.
- The radio frequency (RF) circuit provides wireless communication of recorded tire pressure data.
- The application-specific integrated circuit (ASIC) is the intelligence of the TPMS sensor unit and conglomerates all inputs, turning it into usable data for the TPMS system–and most importantly, your consumer
In our valves, we are fastidious in our testing and processes to eliminate the conditions that degrade quality and performance of the overall solution:
Rubber tire valves must be ozone resistant to prevent rubber deterioration in the form of surface cracks and, in extreme cases, rubber splitting and breakage throughout the entire rubber part. A common term for ozone attack on rubber is "dry rot." In extreme cases, this can cause a rapid loss of air pressure within the affected tire. Schrader uses a specially formulated rubber compound that provides strong ozone resistance.
The valve stem shown to the right exhibits an absence of adhesion or bonding of the rubber to the brass body insert. Loss of adherence is caused by contaminated brass, improper molding conditions or poor rubber composition. Adhesion is important because it keeps the metal insert in place and prevents loss of air pressure. A stem with poor adhesion may exhibit slow air leaks, bulging of the stem above the rim surface and, in extreme cases, loss of the metal insert and rapid deflation of the tire. Schrader® valve stems are subjected to adhesion testing during assembly to ensure that the stem will provide premium performance.
Caused by worn molds or excessive molding pressures, excess flash creates issues with tire assembly automation and may also interfere with proper seating of the valve within the wheel. Flash caught between the valve stem and the wheel may also cause leaks. Schrader uses continuously well-maintained molds and electronic process controls to ensure that proper molding pressures and temperatures are met each and every time.
Valve deformation is mainly linked to a lack of rubber vulcanization; therefore, Schrader utilizes a specific process able to automatically discard the valve if the cure time or cure temperatures are beyond the required level. During valve production, functional shapes are under video control and mechanical rubber properties are tested.
Creep is caused by applying a load to the rubber before it is fully cured or by using a rubber compound without good compression set qualities. This leaves a permanent change in the surface of the rubber that can become a surface leak path and a potentially hidden inner rubber fault. The load can be applied as the rubber is ejected from the mold due to sticking or later. Schrader uses a rubber compound that is inherently creep resistant, and electronic machine controls ensure a complete cure cycle on all molded valve stems.