To prevent air from being trapped in the tread pattern, tiny vents are drilled through the mold in the corners of tread elements. In a complex tread design, there can be thousands of such vents. Uncured rubber flows into the vent holes and is cured there, giving the final tread a “hairy” appearance. The rubber threads are trimmed off in a final inspection by sharp knives held flat against the rotating tire.
Tire Uniformity refers to the dynamic mechanical properties of pneumatic tires as strictly defined by a set of measurement standards and test conditions accepted by global tire and car makers. The tire is automatically mounted on wheel halves, inflated, run against a simulated road surface, and measured for radial force variation, lateral force variation, conicity, plysteer, radial runout, lateral runout, and sidewall bulge.
The test includes laser or probe inspection of the sidewalls and tread. Both tire and vehicle manufacturers seek to improve tire uniformity in order to improve vehicle ride comfort.
Tire balance measurement is a test where the tire is automatically placed on wheel halves, rotated at a high speed and measured for imbalance.
Large commercial truck/bus tires, as well as some passenger and light truck tires, are inspected by X-ray machines that can penetrate the rubber to analyze the steel cord structure
Finally, all tires are inspected visually for any imperfections (e.g., plugged vents or trapped air) before being transferred to a warehouse. If a minor imperfection cannot be buffed away or repaired, the tire is scrapped.