Tire Sidewall problems of the 2004 Chevrolet Silverado

Kumho tyres on my chevy Silverado developed sidewall splits due to dry rot. Tyres are only 1 year old and have 26,000 miles on them. They did not want the dot numbers. Contacted kumho and they said they weren't concerned. My auto shop said the tyres were unsafe to drive and replaced them. The indifference and rudeness of the kumho customer service person charles and his supervisor was appalling. Absolutely no concern that this could create a potentially fatal tyre failure. Very disturbing and quite a surprise.

(1) driving vehicle on interstate at highway speed, 65-70 mph. (2) tire, interior sidewall failure, of driver side rear. (3) dealer replaced with a new tire, n/c. (4) vehicle unloaded. Tires 17,000 mls wear.