TIRE VALVE EXTENSIONSI have preached endlessly about the importance of proper tire pressure and the need to check it before EVERY trip.   However, recently I have received a lot of inquiries about checking the pressure on the rear duals.
First, you will need a GOOD dual-foot tire gauge.   The dual-foot tire gauge will allow you to access the "backwards" tire valve on the outer dual.   While you are at it, get yourself a good dual-foot air chuck and a quality air hose...I through away the stuff that came with my 98 D.
I highly recommend that you purchase two metal tire valve extensions, pictured below.   I had to look around a bit until I found a big rig tire dealer that had these.   These were highly recommended over the rubber / braided rubber extensions that are widely available.   Many people have reported problems with these rubber extensions, especially if they should come unclipped while travelling, which will certainly result in immediate deflation.
For those of you with the Alcoa aluminum wheels, Alcoa also sells an extension and a rubber plug that plugs into the wheel opening to hold the extension in place.   I have not tried this system.
These metal extensions just screw on and do not require anything to hold them in place.   I have been using them for over 32,000 miles with no problems.   But, of course, I check my tire pressure before every trip, no matter how short.
Here is a picture of the installed metal tire valve extension.   Sorry for those really dirty aluminum wheels!
Submitted by Bob Cook