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Open Roads Forum  >  Class A Motorhomes

 > Definition of "under inflated".

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D.R.Bain

Michigan

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Joined: 11/14/2006

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Posted: 11/07/09 05:31pm Link  |  Quote  |  Print  |  Notify Moderator

enblethen wrote:

Under inflation should be bases on actual vehicle load and calculated against the tire manuafactuer's inflation guide for that tire.
I throw the rig's inflation chart in the recycle bin. It is for the best ride.
Remmeber to, that the sidewall marking on many are not maximum but minimum inflation.


Actual under inflation should be based on what has happened to the tire. If you have internal sidewall damage or, the tread is worn on the edges but still has some left in the middle this is under inflation.


Dan, 2007 Damon Daybreak 3270


D.R.Bain

Michigan

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Posted: 11/07/09 05:40pm Link  |  Quote  |  Print  |  Notify Moderator

For answers to the question or to muddy the waters further here is a few websites to read.

http://www.aa1car.com/library/tirepres.htm

http://www.insure.com/car-insurance/tire-safety.html

http://www.highbeam.com/doc/1G1-115279696.html

Starburst2

White Rock, BC, Canada

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Posted: 11/07/09 07:34pm Link  |  Quote  |  Print  |  Notify Moderator

Hi
Many posters talk as though this is a black and white issue. I don't believe it is. I have Goodyear tires on my DP. I weighed the coach as per the standard routine and set the front and rear pressures as per the tire manufacturers charts on their website. I kept experiencing abysmal service life from my tires. I reweighed my coach several times and always came up with the same weight distribution. When replacing my front tires the last time I disscused this with the Goodyear tire shop manager. He said the premature wear was due to under inflation. I showed him on the Goodyear website in his office that the pressure I'd been running was as per the manufacturers chart which called for 85 psi. He told me to run 97 psi rgardless and I do. I have now experienced proper tire life without abnormal wear.
Who do you believe?
Lloyd

Jack M.

Calgary, Alberta, Canada

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Posted: 11/07/09 07:43pm Link  |  Quote  |  Print  |  Notify Moderator

It isn't rocket science nor a 'definition' issue. My 'opinion' is that anything under the manufacturer's table is under inflated. The optimal pressure, or right or best pressure, is above that based on ride, trial and error, wear, mileage and so on. You tires were not so much under inflated, as not at the optimal pressure for you and your coach. I run my Revolution Goodyear Tires at 110 front and 106 rear, well above the table, but about right for my coach, tastes and needs. Symantics perhaps?


Jack & Nim Myton
'07 Revolution LE, 40E, DSCVRY "Reveille"
`08 CR-V, `RVPUSHR`
Moderator, FMA Revolution Owners Group, Good Sam, FMCA
www.revolutionmotorhome@yahoogroups.com

smkettner

Southern California

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Posted: 11/07/09 07:47pm Link  |  Quote  |  Print  |  Notify Moderator

Less pressure than the GVWR sticker is under inflated IMO.


2001 F150 SuperCrew
2006 Keystone Springdale 249FWBHLS

mowermech

Billings, MT

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Posted: 11/07/09 08:53pm Link  |  Quote  |  Print  |  Notify Moderator

It is really very simple.
Take your coach to an empty parking lot.
Make a mark, or several marks, across the tread of each tire with soft chalk.
Then, drive the coach a few feet.
If the marks are erased on the edges, but not in the middle, the tires are underinflated. Add a few PSI and try again.
If the marks are erased in the middle of the tread, but not on the edges, the tires are overinflated. Remove a few PSI and try again.
If the marks are erased evenly all across the tread, the tires are inflated correctly for THAT load.
Quick, easy, and simple, and no internet searches, no conflicting confusing charts, and no weighing necessary.


CM1, USN (RET)
'94 Dodge 3500 4X2 CTD, 5 speed, 4.10 LS diff., Jacobs Rambrake, 274,000 Miles
'99 Monaco McKenzie 32' triple slide
'95 Tioga 29H Ford-based Class C
Daily driver: '08 Subaru Outback
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Golden_HVAC

Fulltime, CA, USA

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Posted: 11/07/09 10:11pm Link  |  Quote  |  Print  |  Notify Moderator

Hi,
If you read the tire sidewall carefully, it will say "Minimum pressure for maximum load _, _ _ _ pounds or KGs."

The maximum air pressure is actually 10 PSI higher than the minimum air pressure.

You can safely inflate the tire to 10 PSI higher than the minimum pressure listed on the sidewall, and then when the tire is driven, it will get to an even higher pressure when "Hot". This higher tire pressure should not be removed from the hot tires, it is normal, and the tires are built for this pressure.

Also remember that LT tires are speed rated at only 75 MPH or 85 MPH, not 110!

Good Luck,

Fred.

jeep2relax

Lakeside, CA

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Posted: 11/07/09 10:15pm Link  |  Quote  |  Print  |  Notify Moderator

This is what I think of when the term "under inflation" is used.
From www.Goodyeartires.com

Be safe - if a tire has been run 20% underinflated, it must be dismounted and inspected by a trained professional. It should not be aired up without a full inspection or without using a safety cage.

Proper Inflation is determined by weighing and load charts.
It appears 20% below that is really bad.





Sully2

Cincinnati

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Posted: 11/08/09 09:51am Link  |  Quote  |  Print  |  Notify Moderator

under inflation = when inflation pressure is LESS than the amount of inflation pressure that is NECESSARY to support the load(s) placed upon it.


2000 Country Coach Allure; Cummins ISC 330 HP; 71/2 - 8 MPG regardless
2002 Jeep Liberty


Cloud Dancer

San Antonio and Livingston TX USA

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Posted: 11/08/09 09:55am Link  |  Quote  |  Print  |  Notify Moderator

D.R.Bain wrote:

enblethen wrote:

Under inflation should be bases on actual vehicle load and calculated against the tire manuafactuer's inflation guide for that tire.
I throw the rig's inflation chart in the recycle bin. It is for the best ride.
Remmeber to, that the sidewall marking on many are not maximum but minimum inflation.


Actual under inflation should be based on what has happened to the tire. If you have internal sidewall damage or, the tread is worn on the edges but still has some left in the middle this is under inflation.



You might as well say that underinflated is when the tire heats up, and blows out....
Me? I go with the Michelin chart, then I add a couple of lbs to make me feel better.


Willie & Betty Sue
Miko & Sparky
2003 41 ft Dutch Star Diesel Pusher/Spartan
Floorplan 4010
Blazer toad & Ranger bassboat

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