The tires on the Chevy Volt are rated at 51 pounds. As a rule of thumb, I always avoid filling more than 90%. So I filled my tires to 46 pounds. I do not notice any more bumps than usual. It still rides as if it is on clouds. It should handle better, but with the electric steering it rides great no matter what the pressure is.
I did notice a bit more range after increasing the tire pressure from 32 pounds to 46 pounds. I always keep my tires about 10% under max on all my cars with great results, so this is highly recommended.