is suspension mount (rear tires) tilted in causing tire choppiness at 40k miles?

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I experienced excessive road noise after the rear tires were rotated to the front at 80k mi. Tires are 17 Multi-Mile radials. Mechanic said tire tread badly roughed up and I needed to replace the two offending tires. They had gone 40k but I was told they warrantied at 60k when bought less than 2 yrs ago. All regular maintenance etc. done regularly. No off road driving - all interstate or normal city. No accidents. Told cause of bad tire wear was specs from mfgr on suspension of rear tires, titled slightly in on top makes wear faster and rougher. When rotated to front caused noise. . . . need confirmation of this explanation.