[AT] OT truck tires/driveshaft?

[Stephen Offiler]

Firestone tires on that original Explorer (circa '91) has a max pressure
rating of 35psi.  Firestone engineers recommended 28psi for the Explorer.
 Ford dropped that to 26psi to tailor ride and handling characteristics.
 Now add the fact that 99.9% of the driving population never checks their
air pressures, and let a year or two go by, and natural diffusion thru the
rubber has dropped the pressure to sub-20psi sort of levels.  Now we have
created a situation that exacerbated the Firestone's propensity toward
tread separation.  Lots of blame to spread all around in that whole thing.
 It also gifted the driving population with pressure sensors in each wheel
in modern vehicles.

SO



On Thu, May 15, 2014 at 11:35 AM, charlie hill
<charliehill at embarqmail.com>wrote:

> Ron,  the first time I ever heard the idea of running max pressure in tires
> was when Firestone was trying to weasel out of responsibility for their
> tires that were blowing out on Ford Explorers.  I'm not saying their tires
> were
> bad.  I'm just saying that is the first time I heard this idea that tires
> MUST be inflated
> to max pressure.
>
> Charlie
>
> -----Original Message-----
> From: Ron Cook
> Sent: Thursday, May 15, 2014 10:40 AM
> To: Antique tractor email discussion group
> Subject: Re: [AT] OT truck tires/driveshaft?
>
> My long time, now retired, favorite tire dealer once told me when I was
> asking what pressure to run in some tires on a trailer......they need to
> be round with the tread flat on the surface.  Now I admit this was long
> ago enough that we were talking bias ply tires.  It did, however work good.
>
> Charlie has it right.
>
> Ron Cook
> Salix, IA
> On 5/15/2014 7:15 AM, Stephen Offiler wrote:
> > I completely agree with Charlie.  Including his apologies to Jeff.  We
> > *respectfully* disagree.
> >
> > I've lost track of the vehicle in question but I think maybe it's an old
> > F-600.  I'd be surprised to find a tag inside the driver's door listing
> > recommended pressures, but I suppose it's possible.
> >
> > Ah, but then... even if you do have those recommendations, are they
> right?
> >
> > I've got a '97 F-250HD with 8600lb GVWR and a 6500-lb rear axle.  Tires
> > are
> > rated max 3250lb at max 80 psi. (I've always thought it is more than
> > coincidence that two 3250lb tires add up to exactly the 6500lb axle
> > rating,
> > but I digress).   The sticker inside the door says 55psi in front, 80psi
> > in
> > back.  Hmmm.  With 80psi in back I am good to load the axle right up to
> > its
> > maximum, and the truck right up to its maximum.  But it weighs 5400lb
> > empty, meaning I've got 3200lb to play with.  If I am running empty, or
> > running light such a trip to the transfer station with household trash,
> > 80psi in back is just ridiculously high.  I typically run about 50 psi
> > front and rear when empty.
> >
> > As I read thru Charlie's note, I kept thinking to myself "but Charlie,
> > temperature plays a big role" and I was really happy to reach his
> > paragraph
> > about the infrared thermometer.  They are readily available and pretty
> > inexpensive these days.  In terms of light-duty vehicles (which we aren't
> > actually talking about) sidewall temperature is an interesting
> measurement
> > in addition to scanning across the whole face of the tread.  There are
> > some
> > rules of thumb regarding how much you want the sidewalls to warm up.
> >
> > SO
> >
> >
> >
> >
> >
> > On Thu, May 15, 2014 at 6:49 AM, charlie hill
> > <charliehill at embarqmail.com>wrote:
> >
> >> Jeff I know you mean well by posting that and since I don't
> >> remember seeing you post here before I don't want to discourage
> >> you with a negative reply but I just can't agree with that.
> >>
> >> Generally speaking your tires should be inflated to the pressure that
> >> creates maximum
> >> contact with the pavement.   Put a set of load range  E  tires on a
> >> pickup
> >> truck and inflate
> >> them to their max and try to drive on wet pavement.  You'll be lucky to
> >> keep
> >> the
> >> vehicle under control.   I nearly wrecked my truck once when I bought a
> >> set
> >> of tires
> >> out of town at a chain tire store who did just that.  My vehicle
> >> recommended
> >> 36 psi.
> >> The store set them at 50 psi.  I noticed they were very squirrely
> feeling
> >> on
> >> the way
> >> home but didn't think much about it until I hit some rain and nearly
> >> wrecked.  Those tires
> >> weren't Load range E, they were just good quality load C tires with a
> >> high
> >> max pressure
> >> rating.
> >>
> >> I drove a tractor trailer for many years and we always adjust tire
> >> pressure
> >> to load.  Most of the
> >> time we were running heavy loads and when we were dead heading somewhere
> >> and
> >> it started
> >> to rain we had to be very careful.   Tire pressure is often adjusted
> down
> >> for running off road on
> >> soft surfaces as well.  In fact, some tractor trailers now come with a
> >> rig
> >> that allows them to adjust
> >> tire pressure from the cab of the truck.
> >>
> >> Running too much pressure (just because the tire says you can) will
> cause
> >> premature wear in the
> >> center of the tire as well as making the vehicle hard to handle.   If
> you
> >> really want to know how to
> >> precisely set your tire pressure get yourself an infrared thermometer,
> >> drive
> >> the vehicle until the
> >> tires are warmed up good by going around some curves.  Then stop and
> have
> >> someone take
> >> temperature readings across the face of the tire.  If the temps are
> about
> >> the same on all of the
> >> treads you have them right.  That is how race teams set up their cars
> for
> >> racing assuring they
> >> have maximum tire contact.
> >>
> >> Others might have different opinions but I know what has worked for me
> >> for
> >> a
> >> few million miles
> >> in all sorts of vehicles.
> >>
> >> Charlie
> >>
> >>
>
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