I bought 4 Solar 4SX tires in 2016 for my 2005 Jetta. I have no complaints. They shed water pretty well on wet roads and I don't notice any difference between them and the more expensive Goodyear tires I had on the car last. I looked online a few times to try and figure out who made them. I bought them pretty cheap from a Walmart and I was always concerned that they might have been from one of the low-end Chinese factories. After looking on line some more and reading the side walls on the tires, I figured out that mine were made in a factory with the code "7T". That factory is in Indonesian owned by "P.T. SUMI RUBBER INDONESIA". They are owned by the Sumitomo Corporation. Sumitomo is a standard Japanese tire manufacturer who makes low end off-brand tires (e.g. Solar) up to some high-end stuff.
So, I now feel pretty good about my cheap tires. I think (wrong or right) that when you get the off-brand tires from the major manufacturers (Goodyear, Bridgestone, etc.) you get the best deal, as long as you aren't looking for the highest performance tires.
Anyway, mystery solved for my tires. But, keep in mind that I don't know the whole story behind the Solar tires. They might have other manufacturers provide them products. I just know that my tires are off-brand Sumitomo tires.