Z G2

Had my first set of Nokian Z G2 215/55ZR17 (Made in Russia) fitted on my car for the past 4 years after reading the good reviews. However, after the 2nd year or approx 20,000 miles of rolling on city (70%)/highway (30%), the tyres became quite noisy. After the 3rd year, the tyres show signs of cracks and uneven wear although I performed wheel balancing and rotation for every 10,000 km. What surprises me is the tyres had very uneven wear and the inner blocks surface were high and low during one of the my regular wheel balancing and rotation. Mechanic checked my wheel alignment and there is nothing wrong. TIll now, I do not know why this set of tyres have so much uneven wear. I have used different types of tyres in the past (bridgestone, yokohama, michelin, falken, goodyear, dunlop) but never encounter this phenomenon before, Although the wear indicator is still showing 5 to 6 (almost new) for the tyres with 70% thread depth left, I decided to change the tyres as the tyres was getting too noisy.