Help

I had two tires installed on the rear of the c63. They were told to put Continental Conti Sport 5p on which was original equip. The put on Conti Sport Contact3, which is the tire, from last year and before.One dealer said he could not get the Conti Sport 3 anymore. My concerns are will the Conti Sport 3 last as long and ride and perform as good as the 5p? Second I don't want to have a flat somewhere and the only tire available is the 5p and have mismatched rear tires. I found out the expensive tire wheel coverage is not what I thought. The origianl warranty is just as good and didn't cost a thousand dollars. Neither one will replace the tire when it reaches 1/32.