Tire Pressure

We have a 2007 2720SL with 14" radial tires - it was a repo and we are assuming the tires are the original ones. According to what we read about TM tires - they say 55 psi is sufficient. However, from what I have read on the forum I see that some inflate to 63 or 65 psi. We will be traveling on highway road most of the time. Our tow vehicle is a 1500 Chevy Silverado.
Again this is only our 2nd trip out in our TM and we are still learning. Thanks in advance for any advice sent our way.
T