Lots of talk about tire traction. But, have you considered that the tire is only part of the traction equation?
Apart from a major consideration of a CLEAN road surface, not all road surfaces are cement. Even if it is, the surface finish on cement can vary with age and wear. Cement can become glossy, and slick.
Then there are composite roads where an aggregate is combined with a binder, and then rolled flat.
There are variations in the binder formula, Asphalt, oil, etc., which all change properties as they age and weather. And then there is the aggregate to consider. Often, it is whatever is cheaply available in the local market place. Areas of the south US, use crushed coral, another crushed stone. It could be a filler of many types, including sand, gravel, crushed stone, slag, or recycled crushed concrete. These filler materials have different friction coefficients, as well as the binder.
When people say their (insert hated tire brand here) lost traction, could it be that the brand they had, used a rubber compound that didn't work well with the road surface composition deployed in the area in which they ride?
I specuate that at some point in time Cheng Shin tires were manufactured for the Chinese market place. Further, these tires were intended for under developed roads, perhaps gravel instead of hard surface roadways. Gravel roads will cut up soft rubber tires rather quickly. I suspect Cheng Shin used a hard compound with added silica for durability in such marketplaces. When the export market became an option, these hard compound tires made it to countries which had many more hard surface roadways where traction is far greater than what can be had on a gravel road. Softer rubber compounds could survive longer, AND provide more traction than a hard compound made to survive gravel or unimproved roadways.
So, rather than brand bashing in general, might it be a better question of what rubber compound works best for the roads you intend to ride upon? What are YOUR roads made of?
Cheers,