[AT] OT truck tires/driveshaft?

Thu May 15 05:15:23 PDT 2014

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
>
> -----Original Message-----
> From: Jeff & Ginny Pomije
> Sent: Wednesday, May 14, 2014 10:16 PM
> To: at at lists.antique-tractor.com
> Subject: Re: [AT] OT truck tires/driveshaft?
>
> Can't speak to the vibration, but tires show the max PSI that they can
> handle.  That is not the same as what is recommended by the vehicle
> maker.  Usually on the driver's door frame of vehicles is a tag that
> gives the recommended tire pressure for that vehicle.
>
> Jeff Pomije
>
> On 5/14/2014 8:39 PM, jtchall at nc.rr.com wrote:
> > Dropped the air pressure in the front tires to 65 and the vibration
> > dropped
> > to tolerable levels, at times not even noticeable. I had close to 80 in
> > the
> > tires, I'm thinking the tires call for 85 or 90 psi. The guy that sold me
> > those tires says 65 should be fine. I don't understand the discrepancy
> > between what he is telling me and what is listed on the tire.
> > Could vibration with higher pressure be a sign of bad shocks (I guess it
> > has
> > them on the front, haven't looked). Anyway, got a small load of scrap
> iron
> > I
> > need to haul. Not enough weight to load the truck but I should be able to
> > get an idea if the vibration is going to be tolerable.
> >
> > John
> >
> >
> >
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