[a/s] Tire inflation pressures

[Susi and John Burchard <saluqi@xxxxxxxxxxxxx>]

Hi all,

Can someone tell me the correct inflation pressures for 8R19.5 radial tires,
load range F, for a motor home loaded to the following weights per tire:

front singles 2260 lb
rear duals 1795 lb (per tire, not per wheel!)

The total road-ready weight of the MH is 11,700 lb, of which 4520 lb is on the
front axle, and 7180 lb on the rear.  That is by actual weighing on a truck
scale.  4520/2 = 2260; 7180/4 = 1795.  The GVWR for this vehicle is 12,500 lb. 
The GCVWR is 19,000 lb but does not enter into this situation because when I tow
(a toad) it is on a tow bar which adds no weight.

There is a table in the owner's manual, which appears to be for bias ply tires. 
There is a table in the Livingston repair/maintenance book with data for radials
too, and that table seems to indicate that 45 psi front and rear would be the
recommended pressure.  That looks to me like serious underinflation.  That same
table gives load/inflation pressure values for LR D and LR E, indicating that
inflation pressure for a given load is the same regardless of the load range. 
Does that also apply to LR F?

I think LR D would be recommended for this application, but 8R19.5 LR D tires
are hard to find, or next to impossible.  I have only ever seen one set, and
they were on an old motor home.  I never found any I could purchase.  All the
19.5 inch radials I have found for sale were LR F.  That is also what was on the
motor home when I bought it (used).

Observation of wear patterns on the existing tires suggests they might develop
an "underinflation" wear pattern at anything less than about 85 psi.  I also
have the feeling, however, that very hard tires put considerable stress on the
interior fittings of the motor home.

So I am thoroughly confused.  Help!

John

Susi and John Burchard
Tepe Gawra Salukis
saluqi@ix.netcom.com