The chance of getting hit by lightning is about the same as winning the lottery. It just feels a lot different.
Your tires aren't going to help. If lightning strikes your car, it's not the tires that insulate you. The cage of the car is like a Faraday Cage. Since electricity always follows the path of least resistance, that happens to be down the outside of the car and away from you. You don't have the same luxury on a bike.
I don't like riding during a thunderstorm. I have. It's not pleasant. If I have to I will. But I prefer to wait a bit and let it blow over.