I had a problem with a set of Shinko's a while back.
The way that Shinko handled the problem really instilled a lot of confidence in me.
They sent me a new set of tires and only asked that I drill holes in the sidewall of the old tires and send them pics.
Same here my new Shinko SE890 Journey rear tire kept loosing 3-5 psi every 2-3 weeks even when new installed at local cycle shop. Sprayed with soapy water and found 3 places along the rim on one side that has 3 very, very tiny bubbles coming out from the bead, but only on one side. Even after 1 year of use, they sent me free of charge a new Shinko SE890 Journey. All they did was tell me this year that when you decide to take it off, to have shop or me take pics of the 3 places it leaked around the rim both on my rim and the old shinko tire for any defects and send them pics back is all to determine if bad rim, bad install, or bad tire bead in those 3 areas.
Either way, not much hastle Shinko rep calling their 1-800 number was fine with me sending pics of 1 year old shinko tire with 80% tread left as well as soapy bubble leaks on that one side.
It could very well be bad install if for some reason say the shop guy did not clean the rim fully and left particles of dirt or sand in those 3 spots? or more my guess is there is a very, very tiny defect in the bead of the shinko tire in those 3 spots. I doubt it is a bad rim, but never know?
I am sticking with Shinko until they prove me otherwise for price paid cannot be beat. Last as long as the rest (except car tire) at over 1/3 off the other tires.