RE: [A/S] Metal Valve Stems

["David & Bret" <dtbw_1999@xxxxxxxxx>]

Bill,
Our '02, 19' Bambi (single axle) has a gross weight of 4500lbs on an axle
rated to carry 4300lbs (the difference is 500+lbs of hitch weight, which is
carried by the tow vehicle).  The recommended tire pressure from A/S is
65PSI.  According to Goodyear, the ST225/75R15D tires recommended for our
trailer (and what it has on it), 55PSI (ie 2150/tire) would NOT handle the
max load.  At 60 PSI, they are rated at 2380lbs/tire, which would give me
the slightest margin and at 65PSI, they are rated at 2540/tire, which still
only gives a total of a 500lb margin over the gross weight of the trailer.  

Just because a tire is recommended to run at max pressure, does not mean you
need bigger tires.  Higher load range tires have stiffer rides and that
requires beefier suspension on the trailer and a rougher ride for the
contents. The ST225/75R15D is also the largest tire that will fit within the
confines allowed by Airstream on my rig.

A good friend just took delivery on a new 2005 28'CCD which runs the same
tires and suspension as our Bambi but with tandem axles and A/S recommends
65PSI inflation for those tires as well.  

Not sure which tire you are running, but gauging from the info in your post,
it would appear that you have ST205/75R15D tires.  Goodyear shows that those
tires at 35PSI will support 1430lb/tire, so that gives a total weight
carrying capacity of 5720.  The Airstream recommendation of 36 would give
the tires just a bit more capacity, so that looks logical.  But it also
means that if a tire gets the least bit low on pressure you now have a
condition where the tire is no longer able to support it portion of the
weight and will run hotter, which overtime will lead to failure.  It also
puts more stress on the other tires as some of the load transfers to the
other tires.  While there would certainly be no need for running at 65PSI on
your rig, I would certainly feel a lot more comfortable with 40PSI.  

david