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Old 07-19-2012, 12:29 AM
chris199 chris199 is offline
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Default Tire Pressure ....confused.....

I thought I understood..now confused by Good Sam info....
" Set inflation pressures (Note: the amount of air pressure you need depends on the weight of your fully loaded vehicle. Use the vehicle’s recommended pressure, not the pressure indicated on the tire which is usually the MAXIMUM allowable pressure)"

Have cougar 29rev...sticker says tire pressure should be 65 psi. Should I really inflate lower?

Was being diligent, using tpms, keeping it to 60 to 62.

Now what?
I believe tires are Towmax
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Old 07-19-2012, 02:54 AM
therink therink is offline
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Hi, if your Towmax tires are load rated "D", then they should be inflated to 65 psi cold. Running the tires with lower psi will make them run hotter and shorten their life.
I just dumped my Towmax D's and replaced them with Maxxi E's, which are rated at 80psi. The sticker on my fiver says 65 psi, but that sticker assumes that D's are installed. I run my E's at 80psi.
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Old 07-19-2012, 05:35 AM
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Jim W Jim W is offline
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Quote:
Originally Posted by chris199 View Post
I thought I understood..now confused by Good Sam info....
" Set inflation pressures (Note: the amount of air pressure you need depends on the weight of your fully loaded vehicle. Use the vehicle’s recommended pressure, not the pressure indicated on the tire which is usually the MAXIMUM allowable pressure)"

Have cougar 29rev...sticker says tire pressure should be 65 psi. Should I really inflate lower?

Was being diligent, using tpms, keeping it to 60 to 62.

Now what?
I believe tires are Towmax

What you should really do is weight each tire and axle load of a fully loaded trailer. Than the highest loaded tire weight for each axle will determined what the tire pressure should be.

As an example say you are using Michelins XPRIBS on you trailer, that are LT245/75R/16 LRE size tires. You need to weigh them individually to find out the proper load that that tire is supporting. Now one side of the axle tire load is 2600 lbs and the other side load is 2900 lbs than you will need to inflate the tires of that axle to 70 PSI. The 70 PSI will support 7625 LBS with this type of tire. The other axle may have a different air pressures depending on its supported load.

This is true for all RV tires all though most users of RV’s just inflated them to the maximum tire inflation that is imbedded on the side wall.
Jim W.
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Old 07-19-2012, 07:26 AM
KanTC KanTC is offline
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Chris,

Inhale. Exhale. Relax. Just joking around...

Your trailer has 15" D rated tires (yes, probably TowMax), therefore your trailer sticker AND your tire stamp
should 'both' read 65 psi.

In a nutshell, that GS statement wouldn't apply to those of us with 15" D rated tires, but I can see why it
would be confusing. Now, that said.....

Keep tires inflated to 65, keep speed under 65, and go have fun! No more

Terri, the Chevy co-pilot
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Old 07-19-2012, 07:30 AM
smiller smiller is offline
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Quote:
Originally Posted by chris199 View Post
I thought I understood..now confused by Good Sam info....
" Set inflation pressures (Note: the amount of air pressure you need depends on the weight of your fully loaded vehicle. Use the vehicle’s recommended pressure, not the pressure indicated on the tire which is usually the MAXIMUM allowable pressure)"
That's rather poorly written because first it says to set pressure based on the vehicle manufacturer's recommendations and then it says to adjust pressure for the vehicle's actual weight... and these two values will not always be the same.

Technically the best way is to measure the weight on each tire, yadda yadda, but this usually isn't very practical, and the vehicle is not always loaded the same. In most cases it is best to inflate to maximum pressure (and thus provide maximum weight-carrying capacity) and be done with it. If you see excessive center treadwear (indicating overinflation) you can make an adjustment but usually that isn't a problem.

Last edited by smiller; 07-19-2012 at 07:47 AM.
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Old 07-19-2012, 07:41 AM
Festus2 Festus2 is online now
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Default More confusion?

chris199 -
There is another lengthy thread which I'm sure you've noticed --"All the tire discussion has me terrified and confused" () by X-treme which discusses tires, tire pressure and tire rims.
If you haven't been following it, there are numerous posts in that thread dealing with tire pressure which might shed some light on your question. His thread can be found in the General RV Issues section of the forum.
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Old 07-21-2012, 01:32 PM
chuck&gail chuck&gail is offline
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Quote:
Originally Posted by Jim W View Post
What you should really do is weight each tire and axle load of a fully loaded trailer. Than the highest loaded tire weight for each axle will determined what the tire pressure should be.

As an example say you are using Michelins XPRIBS on you trailer, that are LT245/75R/16 LRE size tires. You need to weigh them individually to find out the proper load that that tire is supporting. Now one side of the axle tire load is 2600 lbs and the other side load is 2900 lbs than you will need to inflate the tires of that axle to 70 PSI. The 70 PSI will support 7625 LBS with this type of tire. The other axle may have a different air pressures depending on its supported load.

This is true for all RV tires all though most users of RVís just inflated them to the maximum tire inflation that is imbedded on the side wall.
Jim W.
We have weighed each wheel, set pressure to TIRE MANUFACTUERES recommendation for that load (per axle as said above) plus 5 psi for luck. Worked great so far for over 200,000 miles with only issues being a few repairable nail punctures.

Having said that, NONE of those miles were using Chinese tires. It is a choice.
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Old 07-21-2012, 01:59 PM
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JRTJH JRTJH is online now
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If you do decide to use the axle weight to establish tire pressure, make sure you're loaded the same way all the time and that when you do weigh, that the trailer weight is a "true representation" of what you really will be towing. Through the camping season the amount of "stuff" will increase as will the trailer weight. There's people on here who readily admit that they are still carrying "stuff" out to their trailer before almost every trip. Holding tanks are "sometimes full, sometimes empty, etc... All of this can dramatically change the axle weight of an RV.

So, if you reduce the pressure to a "calculated axle weight" make sure the weight stays where you "calculated"

For most of us, it's simpler and much more efficient to go with the pressure recommendation of the trailer manufacturer (for the factory installed tire size) or to go with the max pressure recommended by the tire manufacturer (for increased tire size) Monitor for tread wear with an accurate treat measurement tool and if the center of the tread wears faster, reduce pressure to accommodate, but not below the manufacturer's recommendation. I've never had that occur in 40+ years of towing.

ST tires aren't like LT tires. They have a different sidewall construction and flexing of the sidewall creates heat which is any tire's enemy. In LT tires, if you add more weight, you add more pressure to support it. Although that "can be applied" to ST tires, to really be at the "gnat's behind" on pressure, you'd need to reweigh every tire before every trip (assuming the loaded weight changes) it's just simpler to run ST tires at the recommended pressures...

Just my practice and so far, I've been able to avoid any problems with tires..... your view may vary
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Last edited by JRTJH; 07-21-2012 at 02:03 PM.
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Old 07-21-2012, 03:38 PM
GMcKenzie GMcKenzie is offline
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I just inflate to the sidewall rating.

But, there is an old trick that may work well here,

Get a piece of chalk and make a line across the tread (from sidewall to sidewall). Roll the trailer forward a few feet so the tires rotate a few times. Look at the line. If the center rubs off faster, you are over inflated. If the edges rub off faster you are under inflated. The line should rub off uniformly for each tire. If one edge rubs off, you've got an alignment issue.

Make sure to do it with a normal load and completely hooked up.
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Old 07-21-2012, 06:25 PM
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CWtheMan CWtheMan is online now
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Here is a NHTSA reference that tells the reader straight out who is responsible for setting correct tire pressures. Remember, correct and recommended tire pressures are synonymous.

I post this reference because it makes it very clear that tire manufacturers DO NOT set tire pressures.

http://www.safercar.gov/Vehicle+Shop...nd+Load+Limits

Almost all load inflation tables found on the internet are without instructions. Thatís because they were written for the tire industry at large. On the same line, using scaled weight in conjunction with load inflation tables is also almost always without instructions. The key instruction missing is when using load inflation tables to adjust tire pressures is to NEVER use less than the recommended tire pressures found on the vehicle labeling or itís ownerís manual.

Vehicle tire pressures all revolve around the same regulations and the procedures remain consistent across all designs.

CW
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