First I got the truck in Dec. It had 50 PSI in all tires the tires seem to have worn even in 15,000 miles. I was going to put 70 PSI in them. Well I did except the inner rears. How do you get the valve stem cap off? Is there a valve extender or do you need to pull the tire off? Opinions on the pressure? I carry abouyt 1000 pounds and pull a car trailer with a Vette. Thanks!