Another tire pressure question - Ventana LE

[canipeb]

This forum has been great for a newby to learn about tire pressure and I know I need to go and get my RV weighed and then look at the tire manufacturer recommendations. However, I will be taking a trip in two days and need to set tire pressure and will not have an opportunity to weigh it beforehand. The panel by the driver's seat says 130psi front and 120psi rear. That just seems like alot to me. The tires show a max psi of 120 I believe.

Two questions:
To be safe would you suggest 110 psi? Something else?

The dash has a psi dial that shows left and right psi. However, it doesn't specify if this is for the front or back or what it is measuring exactly. Will search again through the manual but thought someone may know off the top of their head.

Thanks

[reubenray]

I would like to know this also. I will be picking up my new Newmar in about a week and I won't be able to get it weighed before I bring it home.

[RMD3819]

Can't help you with tire pressure but lots of good info in this thread:
http://www.irv2.com/forums/f258/tire...in-336372.html

I would not exceed the 120 that is on the tire. Make sure you are looking at the Newmar sticker and to the Freightliner one.

The psi dial is the air pressure in the air brake system. It has nothing to do with the tires.

1-front
2-rear

[canipeb]

Originally Posted by RMD3819

Can't help you with tire pressure but lots of good info in this thread:
http://www.irv2.com/forums/f258/tire...in-336372.html

I would not exceed the 120 that is on the tire. Make sure you are looking at the Newmar sticker and to the Freightliner one.

The psi dial is the air pressure in the air brake system. It has nothing to do with the tires.

1-front
2-rear

Thanks for the quick response. I thought those dials could be the air brakes. Sounds like I need to get a TPMS setup.

[cruzbill]

Danger with tire inflation is too little pressure = too much heat=tire explodes.

The 120 psi 'max' on the sidewall is this:

the MINIMUM pressure required for the MAXIMUM WEIGHT as listed on the tire sidewall.

120 is NOT a maximum pressure not to be exceeded.

Until you get your rig weighed, I would go with the pressures listed on the sticker. Running a tire even 10% under inflated is not recommended.

[GaryKD]

Hi canipeb,
My PSI settings are:
Front is 100 PSI at 11.8K weight
Rear is 90 PSI at 20K weight
These are verified corner weights.

You can take away from this the rear is at GAW (20K). You should be no more than this. The front is a little more difficult. My GAWR is 12.5K. For me you could run:
Front at 110 PSI
Rear at 95 PSI
and be comfortable.

Take a look at the Michelin chart for your tires. Compare it to the GAWR of your coach. Make your choice. What cruzbill posted is true. Also true is excessive air means more stress on the tires and suspension. Along with a very hard ride.

[reubenray]

Originally Posted by canipeb

Thanks for the quick response. I thought those dials could be the air brakes. Sounds like I need to get a TPMS setup.

I have one, but it does me no good until I get the motorhome weighed.

[hrt]

I've seen a lot of posts talking about the psi values on the chart on the wall. Am I the only one who has two charts on the wall? The freightliner one has pretty high numbers, like 120 for the rears. The newmar one lists much lower pressure, like 85psi for tag and 95psi for the rear tires.

[Mr_D]

Originally Posted by canipeb

This forum has been great for a newby to learn about tire pressure and I know I need to go and get my RV weighed and then look at the tire manufacturer recommendations. However, I will be taking a trip in two days and need to set tire pressure and will not have an opportunity to weigh it beforehand. The panel by the driver's seat says 130psi front and 120psi rear. That just seems like alot to me. The tires show a max psi of 120 I believe.

Two questions:
To be safe would you suggest 110 psi? Something else?

The dash has a psi dial that shows left and right psi. However, it doesn't specify if this is for the front or back or what it is measuring exactly. Will search again through the manual but thought someone may know off the top of their head.

Thanks

The pressure on the sidewall of a Michelin RV tire and many others is not the "Maximum" cold pressure the tire should ever have (unlike car tires) it is the minimum to support the maximum rated carrying capacity of the tire. NHTSA defines truck tires as those rated for vehicles over 10,000#'s GVWR.

From the Michelin RV Tire Guide:

"If you look at the tire's sidewall, you'll see the maximum load capacity allowed for the size tire and load rating, and the minimum cold air inflation needed to carry the maximum load."

From page 6 of the GoodYear RV Tire and Care Guide:

"How much air is enough?
The proper air inflation for your tires depends on how much your fully loaded RV or trailer weighs. Look at the sidewall of your RV tire and you’ll see the maximum load capacity for the tire size and load rating, as well as the minimum cold air inflation, needed to carry that maximum load."

From TOYO:

Q: What are the consequences of inflating the tires to accommodate the actual loads?
A: If the inflation pressure corresponds to the actual tire load according to the tire manufacturer’s load and pressure table, the tire will be running at 100% of its rated load at that pressure. This practice may not provide sufficient safety margin. Any air pressure loss below the minimum required to carry the load can result in eventual tire failure.

But then they go ahead and publish a weight/pressure chart allowing lower pressure for RV's!!

From the August 2010 Motorhome Magazine "Tread Carefully" tire article:

The maximum load capacity allowed for the size tire and load rating and the minimum cold air inflation needed to carry that maximum load are located on the tire’s sidewall.

From our owners manual:

Federal law requires that the tire’s maximum load rating be molded into the sidewall of the tire.
If you look there, you will see the maximum load allowed and the cold air inflation pressure required to carry that stated maximum load. Less air pressure restricts the tire to carry a lighter load.

[snowhawk2]

Originally Posted by canipeb

This forum has been great for a newby to learn about tire pressure and I know I need to go and get my RV weighed and then look at the tire manufacturer recommendations. However, I will be taking a trip in two days and need to set tire pressure and will not have an opportunity to weigh it beforehand. The panel by the driver's seat says 130psi front and 120psi rear. That just seems like alot to me. The tires show a max psi of 120 I believe.

Two questions:
To be safe would you suggest 110 psi? Something else?

The dash has a psi dial that shows left and right psi. However, it doesn't specify if this is for the front or back or what it is measuring exactly. Will search again through the manual but thought someone may know off the top of their head.

Thanks

This should help. We had a 2016 4037 LE and we had 4 corners weights done in Gaffney at Freightliner. The coach weighed in around 33K fully loaded and their recommended tire pressures were 125 in the front and 100 in the rears. The tires I had and rims were good to 130 psi. The tire psi on the sticker from Newmar is the max inflation cold and not the recommended tire pressure based on your actual weight. They put the max pressure on all of their stickers for liability reasons and I have seen it that way on at least 6 coaches. If you run. your tires at the max inflation is will ride very hard and be hard on our coach. Good luck and I hope this helps.

[TJ]

Weighing your rig is the only way to know what tire pressures are appropriate. Sometimes, you can find a state weigh station for trucks that is closed for the day but has the scales left on. I've found several in Washington state. With some careful maneuvering you can usually manage to weigh all four corners. Alternatively, any major truck stop with scales can give you corner weights.

Understand that you need to weigh your rig fully loaded as it will be when you are using it. I make it a point to periodically weigh my rig because it seems things are always being added to the load; usually by my faithful co-pilot.

If you can weigh your rig before setting out on our trip, use the listed tire pressures until you can get the corner weights.

TJ

[jimbo2013]

I did the 4 corners

Front at 110 PSI
Rear at 95 PSI