Tires: 50/80 Psi on 3/4 ton pickup driven mostly empty, tire placard, tire inflation

Question
Hello.  I have a 2003 Chevrolet HD1500.  Tire placard recommends 50 psi front, 80 psi rear.  It has the recommended stock 245/75/16 LT Load range E tires.  Since this truck is usually driven with a mostly empty bed, the rear/centers of my first set of tires began to wear very prematurely, a classic over-inflation wear pattern.  Not to mention rougher than necessary ride and poor rear traction.  After I discovered the wear pattern I started running 50PSI all around.  Center wear slowed and ride and snow/rain traction improved.  Obviously on the rare occation I fill the bed with dirt/rocks/bricks I crank them up to 80 again for that usage.  I'm very careful about maintaining/rotating and checking pressures.  I just got 4 new tires and am planning to do the same to minimize wear and improve ride/traction.  My question is this:  Do you see any problem with this rear 50 psi approch for the majority of my light-load travels, as long as I'm careful about recognizing that heavier loads need a rear PSI increase?  do you have other recommendations?  Thank you!

Answer
Dear Andrew,
Thank you for using AllExperts.
I appreciate that you have an understanding of the relationship between the tire's inflation and load capacity. Many don't.
Having said that, GM's recommendation for 50/80 psi may not be based exclusively on achieving load capacity as the tire inflation will also play an important part in vehicle handling, braking for example.  
The pressure differential between front and rear may not necessarily be due entirely to load difference, and may in part be established to give your truck a certain amount of 'understeer' for example (a desirable handling quality in most cases).  Tire inflation also plays an important role in hydroplaning resistance (heavy rain), and by lowering the psi, you have made the rear tires more prone to hydroplaning.  It is important that the rear tires especially not lose traction in heavy rain before the front tires otherwise 'oversteer' may result (rear-end comes around).  See the attached link explaining the relationship of tire psi to hydroplaning.
Since unpredictable handling in certain weather conditions could result, I'm going to "go by the book" on your truck's original psi recommendation, and I'm also quite confident that GM doesn't want to reduce these pressures regardless of the loads carried.

http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=3