I'm a little oblivious to what the obligations of a car rental agency are required to provide me when I sign the agreement. This was my first rental but, last minute personal vehicle problems and a tight schedule forced me into making the rental. I was in a hurry to make a scheduled trip and the car was a 2009 Nissan Altima so, I assumed it was in good condition. It had 40K miles. Once on the road at highway speed, I noticed a "shimmy" which felt like an unbalanced tire. I noticed there was a dashboard warning light indicating something possibly wrong with a tire. I called the rental office asking what this light meant. I was told it was an air pressure sensor indicating unequal tire pressures. I was told to bring the car by the office and they would check. I told them that was going to be difficult since I had started the trip and was on a schedule. So, at my first stop, I looked at the tires. Three of the tires were Continental brand requiring 44 psi and the left rear was a Yokohama requiring 32 psi. I borrowed a tire gauge and found one tire was actually up to 50 psi and the Yokohama was up to 40 psi. I also saw the tread depth was very low and the right rear tire was cupped on the inside very badly. I assumed this cupped tire was the culprit of the vibration I was feeling at highway speed. Plus, on the trip home, it rained in western Kansas and there was some definite hydroplaning happening. What sort of responsibility and liability does the car rental company have when supplying rental cars? IMO, these tires were worn well past being safe.