The manual for my 1997 Airstream Land Yacht 33 states that the tire pressure should be 65PSI. The tag on the drivers door states that the pressure should be 80PSI. The manual and the tag appear to both be Airstream publications. Both give the tire size as 225/70R19.5. Which one is the correct pressure?
Tire Preassure conflict
- Thread starter geode
- Start date
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Larry N.
Well-known member
Get the vehicle weighed, then look up each axle's weight on the tire manufacturer's chart to see their recommendations. Chances are the correct pressure will be between those two extremes that you mention.
WILDEBILL308
Well-known member
I would stay with the higher pressure until you have the axel weights so you can set them to the tier manufactures recommendations for that weight. I would add a extra 10 lbs. for safety margin and to allow for temp and altitude variations.
Bill
Bill
John From Detroit
Well-known member
Neither of course.. With one exception any printed or molded pressure you read is likely WRONG.
That one (And this is not nearly as important on trailers) is this.
Definition time: Wheels can be single or dual tire...
Now, Scale it.. Weighing EACH weel (or weigh the full axle and then weigh one side and subtract to get the other)
NOTE: Dual axles close together can be treated the same a single unit (one wheel) no need to measure each tire)
Now download the tire's inflation chart from the tire's manufacturer
If is it a single tire wheel be it one axle or two close spaced.. Use the single tire chart
If it's a duel tire wheel use the duals chart
From this you can figure out the proper pressure per the tire maker's.. NOTE for the same size tires this may vary maker to maker.
Some folks likle to add 5 PSI.. Myself among them.
As I said. I do not think this is as important on a trailer as a motor home. but the proper inflation, which varies depending on how the trailer is loaded (I should have said load the trailer as though setting out for vacation) means the full tread is on the road, Full contact.. Best control, and in theory best tracking.
Over inflation means only the center of the tire contacts the road,, Faster wear (in center) less control epically when cornering.
Low inflation means the outer edges take the most wear, Side walls flex excessively and over heat and go BOOM.. Trailer can "Sway" more on the tires to to that excessive flex
But on a trailer.. if I had to choose, go high. Lack of power to the wheels means you won't wear as fast as the tow vehicle does.
That one (And this is not nearly as important on trailers) is this.
Definition time: Wheels can be single or dual tire...
Now, Scale it.. Weighing EACH weel (or weigh the full axle and then weigh one side and subtract to get the other)
NOTE: Dual axles close together can be treated the same a single unit (one wheel) no need to measure each tire)
Now download the tire's inflation chart from the tire's manufacturer
If is it a single tire wheel be it one axle or two close spaced.. Use the single tire chart
If it's a duel tire wheel use the duals chart
From this you can figure out the proper pressure per the tire maker's.. NOTE for the same size tires this may vary maker to maker.
Some folks likle to add 5 PSI.. Myself among them.
As I said. I do not think this is as important on a trailer as a motor home. but the proper inflation, which varies depending on how the trailer is loaded (I should have said load the trailer as though setting out for vacation) means the full tread is on the road, Full contact.. Best control, and in theory best tracking.
Over inflation means only the center of the tire contacts the road,, Faster wear (in center) less control epically when cornering.
Low inflation means the outer edges take the most wear, Side walls flex excessively and over heat and go BOOM.. Trailer can "Sway" more on the tires to to that excessive flex
But on a trailer.. if I had to choose, go high. Lack of power to the wheels means you won't wear as fast as the tow vehicle does.
Mopar1973Man
Well-known member
Gary RV_Wizard
Site Team
I would go with the tag by the door - it is a legally required document and more likely to be accurate than any sales brochure or manual. Besides, always err on the high side with tire pressure. Too little is far, far worse than too much.
Most likely the pressure on the door placard represents what is needed for a fully loaded vehicle (each axle loaded to the max), whereas the owner manual pressure might represent a minimum or more typical loading. The best way to find the right pressure is the get actual weights, as others have already recommended.
Most likely the pressure on the door placard represents what is needed for a fully loaded vehicle (each axle loaded to the max), whereas the owner manual pressure might represent a minimum or more typical loading. The best way to find the right pressure is the get actual weights, as others have already recommended.
elliott-maine
Well-known member
- Joined
- Jan 25, 2013
- Posts
- 378
The info on the sticker tells me to inflate to 110 psi, the max for the tire. The chart from the manufacturer for the weight (each wheel weighed by Smartweigh) says 95 PSI. I compromised a bit at 105 because at 110 the 5th wheel tended to bounce a lot. Just 5 PSI made a difference.
Gary RV_Wizard
Site Team
The chart from the tire manufacturer is the minimum pressure for the amount of load. Most experts recommend more than just minimum, to allow for temperature and altitude variations encountered during travel. That's not a big factor when just driving around town, but RVers tend to travel in more varied terrains and climates, so a bit extra is goodness. Who wants to adjust tire pressure because the weather changed or you drive to another town that is 1000 ft higher in elevation? Nothing wrong if you choose to do daily adjustments like that, but most of us prefer to minimize the need for constant psi adjustments. An extra 5-10 psi covers most situations nicely.
Rancher Will
Well-known member
What is wrong with using the recommended tire pressure as molded on the sidewall of the tire? For over 50 years, with all of our ranch, cars, trucks and RVs, I have always followed the tire pressure recommendations as shown on the tires, with no problems.
Larry N.
Well-known member
Will, while that can work fine, especially on a trailer, on some rigs (my Bounder, for example) there's too much bounce, and it actually became dangerous to drive in many bouncy places.
scottydl
Site Team
Rancher Will said:
It's a comfort factor more than anything. Overinflated tires (more air than needed for the load anyway) will have less flex and less "softening" suspension characteristics. They also contact the road surface less, which can minimize traction potential.
In newer cars you might not notice the harsher ride all that much, but older gas chassis motorhomes can ride/bounce pretty rough on bumpy roads and you want all the extra cushion you can safely get!
Tom
Administrator
- Joined
- Jan 13, 2005
- Posts
- 51,984
The well-meaning dealer tech inflated the tires on our then-new coach to the max (or above), and handling was awful. Things returned to "normal" when we weighed each axle, consulted the tire manufacturer's inflation chart, and deflated the tires accordingly, with a 5-10 lbs fudge factor.
John From Detroit
Well-known member
Rancher Will said:
What is wrong with that is your inability to read an entire sentence.
Maximum Load of 23000 pounds at maximum pressure of 110 PSI (Numbers pulled out of air, not off of tires)
That is the FULL sentence
MOST people.. NOTE MOST people.. Just read ......Maximum pressure of 110 PSI.
When the tire is manufacturered it is not possible for them to give you the proper pressure because they do not know what you are driving, how it is loaded or anything else.. So they give you the maximums.
now the vehicle manufacturer has it a bit better, They at least know what you are driving,, But alas not how you are going to load it.
Thus the ONLY way to be sure is to scale it. This is wny I say 3 pressures all but guaranteed to be wrong are
1: The one molded in the sidewall
2: The one on the sticker
3: The pressure the tire dealer inflated to.
Now sometimes.. You get lucky and one of those is correct.. But not very often.
Gary RV_Wizard
Site Team
Because it is not the RECOMMENDED pressure. It is the max load pressure, as John just explained.
For a trailer, where the tire is typically running at or near its max load anyway, sidewall pressure is a good choice. In other cases, the sidewall pressure might be excessive, perhaps even enough to cause loss of traction, which can substantially increase the possibility of traction loss (skidding). However, I will grant that in most cases the sidewall pressure is no worse than moderately high (unless oversize tires have been installed).
As a sample data point, I just checked our small sedan and big SUV. For the sedan, the sidewall (max) pressure is about 30% above the vehicle manufacturer's recommended pressure, and that recommended pressure itself is sufficient for a fully loaded (at GVWR) vehicle. On the SUV, the sidewall max psi is almost 50% higher than the recommended setting. So in both cases the sidewall pressure is far and away above needs. Probably not dangerous on the sedan, but I believe the SUV would suffer some loss of traction at max pressure. Since it is already prone to front wheel skids and wheel spin during acceleration (it's FWD), I think use of the max sidewall pressure would be really ill-advised.
