Still More on Tire Pressures..

[john bush]

FWIW...

From a safe vantage point, I have absorbed the recent
controversy on tire pressures and now somewhat reluctantly
"crawl out from under the bed" to offer some elaboration
on a point that had left me curious.

We have all read the load capacity rating of "Load
Range E" LT tires being predicated on a MINIMUM of
80 psi--cold. I had not read anything about operation
above that minimum.

Santa Claus brought me a paperback on RV's in general
that has a chapter addressing the care and feeding of tires.
The author cites the same minimum 80 psi requirement
for cold "LT" pressures but on goes further to address
use of pressures ABOVE the stipulated minumum.

He suggests trying another 10 psi (still cold) and running
that way unless there are signs of uneven tread wear
or there is discomfort with the resulting ride. He suggests
the upside includes possible improvements in lateral stability.
.
If anyone is interested in more about this source, contact
me off net and I will forward more detail. Whether his
approach would have the blessing of tire manufactures
is absolutely unknown. I offer no advice based on this
reference. (No, I'm not an attorney, just another engineer.)
Meanwhile, I will retreat to my hiding place "under the bed".

John B. (tire non-expert)
75 PB, Sunol CA

 

[john dolan]

Re: RV author increasing to 90 pounds cold pressure...

>He suggests trying another 10 psi (still cold) and running
>that way unless there are signs of uneven tread wear
>or there is discomfort with the resulting ride. He suggests
>the upside includes possible improvements in lateral stability.

It would be interesting to see some data once Heinz starts collecting
his, since the reduced flexing due to the extra 10 pounds might cause
the temperature to rise to a lower level at operating speed...?

Might be an interesting experiment for someone with really bad wiggle
wagon who has tried everything else, short of going back to bias ply
tires. Correct me if I'm wrong but, if they are recommending 80 COLD,
the tire must be able to take a minimal pot hole or nominal bump while
at 80 COLD or 80+ warm. So if the road is known to be good but causes
wiggle wagon, is that a reasonable risk? Maybe...

Regards,
John 74 Glacier WASH, DC GMC

 

[bright walter]

John, IAW full disclosure, I run 82-84lbs cold tire pressure.


It would be interesting to see some data once Heinz starts collecting
his, since the reduced flexing due to the extra 10 pounds might cause
the temperature to rise to a lower level at operating speed...?

This (lower operating temp) is what you want. I was concerned by
Heinz's post on temp @ 60-65 mph of something like 145 degrees! Is he
running on "B" load range tires? My tires are body temp (or so I think)
under the same condition, I don't have the monitor yet. When I touch them
immediately after stopping, they are luke warm to the touch,everywhere
(tread, sidewall, bead, rim). I am curious if anyone else has the temp
sensor and is getting a temp of anything near 140 degrees.

Correct me if I'm wrong but, if they are recommending 80 COLD,
the tire must be able to take a minimal pot hole or nominal bump while
at 80 COLD or 80+ warm.

You are correct sir! (he said in an Ed McMahon voice). They will take a
pretty big bump too.

walter bright

 

[ron & gina]

> MINIMUM of 80psi--cold

Hi John, I thought it was Maximum of 80 psi cold?
Ron
- ----- Original Message -----
From: John Bush
To: GMC Net
Sent: Thursday, September 23, 1999 3:24 AM
Subject: GMC: Still More on Tire Pressures..

> FWIW...
>
> From a safe vantage point, I have absorbed the recent
> controversy on tire pressures and now somewhat reluctantly
> "crawl out from under the bed" to offer some elaboration
> on a point that had left me curious.
>
> We have all read the load capacity rating of "Load
> Range E" LT tires being predicated on a MINIMUM of
> 80 psi--cold. I had not read anything about operation
> above that minimum.
>
> Santa Claus brought me a paperback on RV's in general
> that has a chapter addressing the care and feeding of tires.
> The author cites the same minimum 80 psi requirement
> for cold "LT" pressures but on goes further to address
> use of pressures ABOVE the stipulated minumum.
>
> He suggests trying another 10 psi (still cold) and running
> that way unless there are signs of uneven tread wear
> or there is discomfort with the resulting ride. He suggests
> the upside includes possible improvements in lateral stability.
> .
> If anyone is interested in more about this source, contact
> me off net and I will forward more detail. Whether his
> approach would have the blessing of tire manufactures
> is absolutely unknown. I offer no advice based on this
> reference. (No, I'm not an attorney, just another engineer.)
> Meanwhile, I will retreat to my hiding place "under the bed".
>
> John B. (tire non-expert)
> 75 PB, Sunol CA
>
>
>

 

[bright walter]

Hello Ron & Gina:

To take advantage of the maximum capability of the load range "E"
tires, you need to inflate them to their maximum recommended cold inflation
pressure, usually 80 lbs. This is/should be the maximum recommended
sidewall presure on most of them. In any event you should put in the
maximum imprinted on the sidewall of your tire, whatever it is (ie 75, 80).
You are correct if you are thinking that in effect the range of recommended
tire pressure is just 80# to maximize tire strenght. At that point, you are
at the peak of the curve of durability. You would drop off in either
direction as you increase or decrease inflation pressure, so the logic of
inflating to that point is sound. As with anything, everyone is free to do
what they want.
Take care, walter bright 76 GB

From: Ron & Gina [mailto:raideron]
Sent: Thursday, September 23, 1999 5:10 PM
To: gmcmotorhome
Subject: Re: GMC: Still More on Tire Pressures..

> MINIMUM of 80psi--cold

Hi John, I thought it was Maximum of 80 psi cold?