My uncle can not drive faster than 85mph. He gets nervous. It is built in some people's blood. Like phobias and what not.
I too get nervous in the triple digits. If your car vibrates, it is time to slow down. I trust the car but I don't trust the tries. Unless it is new or near new, I wouldn't mess around them higher speed limit. My phobia is going high speed and your tires blow out.