[AT] OT truck tires/driveshaft?

charlie hill charliehill at embarqmail.com
Thu May 15 22:58:14 PDT 2014


Good explanation Henry.   Well said.

Charlie

-----Original Message----- 
From: Henry Miller
Sent: Thursday, May 15, 2014 10:25 PM
To: Antique tractor email discussion group
Subject: Re: [AT] OT truck tires/driveshaft?

A lot of discussion, but I figured I'd chime in anyway - most responses are
partially correct, but none are the full truth (I'm not sure I have the full
truth either, but I think I'm closer):

Tire pressure is a compromise.

The right tire pressure means that when your tires wear out after
thousands of miles, the tread wear is even across the entire width of the
tire, and this means you got the most bang for your buck.  Too high
pressure and you wear the center out faster, while too low wears the
outside edge: either way you didn't get as many miles out of your tire as
you could have.  However there is a somewhat large range of pressures
that will achieve this wear.

The less air in the tire, the more heat the tire will generate.  This is 
strictly
a function of the above: your loss in fuel mileage mostly (all?) goes to
heating the tires.  The heat can lead to blow outs.

The more load you have on your tires, the more pressure you need to keep
the tire round.  If you haul a load around you want more pressure.

The more air you have in your tires, the better fuel mileage you will get.
The less air, the lower the fuel mileage.

The more air you have in the tires, the harder your ride will be.  The less 
air
you have the softer your ride.  Car manufactures want to advertise a soft
ride, so their default is to recommended tire pressure is generally as low
as they safely can (unless there is some other consideration).

The more air, the more stable your vehicle is on corners.  (Police training
cars often over inflate their tires so they can train closer to the edge of
stability)

The less air, the more traction.  Off road drivers have been known to drop
pressure down to where the tire is barely off the rim for tricky areas.

The more in the tire, the larger diameter the tire is.  This is mostly
insignificant, but race cars on a circle track can take advantage of this 
for
a few hundredths of a second gain.

In summary:

The tire gives a maximum pressure, do not exceed it. The vehicle
manufacture gives the minimum pressure, never go under it. When you are
hauling more weight you need more pressure.

At times you can violate the above rules, but they are not normal
conditions.

For the record, I optimize for fuel mileage, so I inflate to sidewall 
pressure.
My tires have even wear patterns when I have to replace them. I do not
claim you should do the same - that is your choice.

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