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Old 04-29-2011, 12:52 PM   #1
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Tire preasure

I'm knew to towing a TT instead of a pop up and am curious as to weather I should inflate the TV tire pressure to maximum in order to handle the extra weight?
Thanks for any insight.
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Old 04-29-2011, 01:22 PM   #2
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Well, now, if you don't you will probably have under-inflated tires which causes a bunch of problems. Mostly overheating. (Be sure to check them cold, not after running for a bit.)
I would recommend using nitrogen...but then the nitrogen naysayers will brissel up they hacks and scream about how that is a waste of money...and I'm tired of hearing that!
Jack
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Old 04-29-2011, 01:47 PM   #3
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People typically overload their vehicles regardless what kind they are. Tires that are even slightly underinflated are much more dangerous and prone to troubles than if you run the maximum listed for any given tire all of the time. Your TV should have a sticker located in the door jam somewhere listing your itre pressure.

Once again, measure the tire pressure while the tires are cold.........driven less than a mile.
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Old 04-29-2011, 01:47 PM   #4
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Jack is correct about underinflated tires causing trouble and checking them COLD. (I am a nay sayer about N2)

However, that is not all the story.

Running at max pressure for the installed tires will guarantee the tires are inflated enough to carry the maximum rated load of the TIRE. If your camper weighs LESS than the maximum rated load for the tires, then the tires will be "over inflated". Under inflated tires overheat (as Jack said) which causes delamination of the belts and early failure. It is indicated by excessive wear on the outer edges of the tread due to the center not making good contact with the road.

It is usually recommended to inflate to max because the tires installed by the OEM are the minimum size necessary to carry the maximum certified load of the travel trailer. You will always be safe and the only downside to running a slightly overinflated tire for the camper's actual weight is more camper bounce and increased wear on the center ribs. You might also see infinitesimally better gas mileage.

However, if you weigh your travel trailer loaded for camping and connected to your tow vehicle, and get a REAL weight per tire, you can cold inflate the tires to the actual load needed to be carried. This will reduce bounce and ensure maximum tread contact with the road surface.
The attached inflation pressure vs load chart by Maxxis is pretty generic and can be near universally applied to all manufacturers.

AGAIN, you must WEIGH your rig ready to go to use this chart. What counts is the weight carried by the tires not the truck (another issue entirely). If the weight ticket shows the camper weighs 8000 pounds on the camper axles; then divide by 4 tires to discover the weight being asked of the tires to support. In this case 2000 pounds.

If you had ST225/75R15 C rated tires on your camper you could inflate to 45 PSI (vice 50 PSI) and still be rated for 2020 pounds. As long as you did not exceed the GVW of the camper your could add an additional 130 pounds of stuff per tire, plus whatever the tongue weight increased by, and still be safe if you had used the 50 PSI max pressure.
Attached Files
File Type: pdf maxxis 8008load.pdf (142.2 KB, 40 views)
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Old 04-29-2011, 01:48 PM   #5
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That makes sense but I had to ask, I don't want or need any surprises. Thanks for your insight.
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Old 04-29-2011, 06:57 PM   #6
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The only bad question is the one "unasked."
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Old 04-29-2011, 07:44 PM   #7
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You have already received good information, so I will not re-hash it. I will simply give Lou's post a X2! and add one thing for consideration:

TTs and 5'ers are rarely balanced with their weight. They usually have a heavy side and if not level can have a front axle (nose down condition) or rear axle (nose up condition) carrying more weight than the others. You will not know for sure unless you weigh your trailer and get individual wheel weights. Most CAT scales will just provide axle weights. In general the side of a trailer with a slide out will be heavier. A trailer with two slide outs on one side and none on the other can be quite a bit heavier on the side with the slide outs. I have weighed mine and the slide side is heavier. Without knowing specifics for a unit I generally will run a little higher pressure in the tires on the slide out side of a trailer.

Just my .02
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Old 04-29-2011, 09:18 PM   #8
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Thanks to all for your advice and it has been a great help. You know how it is when you're new to something.... There's nothing like picking peoples brains who've had experience.
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Old 04-29-2011, 10:48 PM   #9
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There is a procedure at CAT scales for weighing individual tires.
Basically, you drive onto the scales several times. The first weigh is full price; subsequent weighs are like a buck each.

So, picture a CAT scale (several plates on the ground). If you drive onto the plates centered and span a pair of scales with your axles you will get the weight on each axle.

THEN, drive off the scales and re-enter. This time drive off to the left or right so one pair of wheels are on the ground (off the scales) and the other pair of tandem wheels are spanning the scale plates. You will basically be weighing the left or right SIDE of your rig.

Subtract the wheels you weighted from the axle weight and you will get the weight on the opposite wheel.

For complete weight and balance, you can do it all in 3 (5 worst case)passes.

1) TV and camper connected with an axle on each plate (if this is not possible due to the spacing you will need one more "Centered" pass to get the camper's tandem wheels on its own plate).

2) TV and camper connected with an axle on each plate "Off Center" (if this is not possible due to the spacing you will need one more "Off Centered" pass to get the camper's tandem wheels on its own plate)

3) drop the camper in the parking lot and drive the TV onto the scales and weigh the truck with an axle on each plate. You can repeat for an individual wheel loading, but I never do.

4) Hook up, pay the man and drive home.

A little bit of math and you will know everything there is to know about your weight and balance for your rig.

The procedure is very similar for Motor Homes.
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Old 04-30-2011, 12:10 AM   #10
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No disagreement that with some manipulation you may be able to come up with information on some scales, but I have encountered some which are not flush with the ground, but are elevated with curbing and/or rails to keep vehicles centered on the scales. I was just pointing out that on most CAT scales, you will not be able to just drive up, weigh and have individual tire weights.

I am not trying to over complicate this. I just wanted to let everyone know that if you have a known weight for your trailer, divide it equally among the tires and use an inflation chart to set your tire pressures, you may have tires on one side over inflated and tires on the other side underinflated.

I have just made it a practice that until I know the weight of a particular unit, I will run a higher pressure in the tires of the side I would expect to be heavier. I know the slide out side of our 8281SS is heavier and I run a higher pressure in the tires on that side.
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