iRV2 Forums

iRV2 Forums (https://www.irv2.com/forums/)
-   Newmar Owner's Forum (https://www.irv2.com/forums/f103/)
-   -   Inflating RV Tires (https://www.irv2.com/forums/f103/inflating-rv-tires-189709.html)

THERAPY GUY 01-15-2014 10:17 AM

Inflating RV Tires
 
Vehicle is a 2007 40' Dutch Star. 400 Cummins. I have tried to inflate the front tires to the 120 psi advised and find that the onboard compressor does not seem to put out that volume when I connect to the air chuck. I have to carry a separate pancake compressor that will do the job. Is there any way to increase the air out put on the coach or is there a secret to achieving the objective that I haven't learned yet. Suggestions welcome.
Thanks

Skip426 01-15-2014 10:30 AM

The 120 PSI , would be an MAX inflation, do you have your axle weights?
Most times MAX is not required for the weight of the axle.
If you get the scale weight of the MH loaded for travel, and inflation chart from the tire manufacturers web site. I think you will find that the MAX is not required, and in many cases results in poor handling.
The engine mounted compressor , will have a tough time with inflation over 100 PSI , and there are several post on the type of compressors other members carry.

tkdavis 01-15-2014 11:19 AM

Guy...I don't know of anyone that runs max air pressure in their MH tires...it's usually much less. As mentioned, handling and ride will be horrible with 120lbs in the tires.

Go to a truck stop with scales (Love's, etc) and have them weigh the coach for you. With the axel weight you can then refer to the pressure chart from your tire manufacturer to get the proper amount of air.

The max psi in my tires is 110lbs and I run mine at 85-90 psi per the chart for my tires and MH weight.

Terry

RickO 01-15-2014 11:27 AM

Yep, as pointed out, on board compressors really struggle over 100 lbs PSI. They'll eventually get a tire a bit over that but it can take forever so many carry dedicated compressors to handle tire inflation.

Also as pointed out... it's highly unlikely that your tires need to be inflated to 120 lbs.

Rick

dennis45 01-15-2014 11:42 AM

Here are a couple of videos that show how to inflate RV Tires off the on board compressor. I have this arrangement and find it works OK. I little slower than a Pancake but gets the job done and does not take up space in my basement.

https://m.youtube.com/watch?v=n5fK54DKWP0
https://m.youtube.com/user/RVgeeks?de...user%2FRVgeeks

hes4all 01-15-2014 08:58 PM

You need to at least know your front axle weight. Preferably corner weight. On my 2006 Mountain Aire I run 95 lbs in the front tires.

Mr_D 01-15-2014 09:02 PM

Quote:

Originally Posted by Skip426 (Post 1885238)
The 120 PSI , would be an MAX inflation, do you have your axle weights?
Most times MAX is not required for the weight of the axle.
If you get the scale weight of the MH loaded for travel, and inflation chart from the tire manufacturers web site. I think you will find that the MAX is not required, and in many cases results in poor handling.
The engine mounted compressor , will have a tough time with inflation over 100 PSI , and there are several post on the type of compressors other members carry.

ON TRUCK size tires the cold pressure on the sidewall is the MINIMUM required to support the maximum weight rating of the tires. Same with the tire charts, it's the MINIMUM cold pressure to support the weight.

From page 2 of the 06/07 Michelin RV Tire Guide:
Quote:

"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 the Firestone/Bridgestone RV tire guide:
Quote:

Bear in mind that these are maximum ratings. The sidewall of the tire shows maximum load and minimum inflation pressure for that load
From the GoodYear RV Tire Guide:
Quote:

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
Quote:

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!!

Mr_D 01-15-2014 09:10 PM

Quote:

Originally Posted by tkdavis (Post 1885302)
Guy...I don't know of anyone that runs max air pressure in their MH tires...it's usually much less. As mentioned, handling and ride will be horrible with 120lbs in the tires.

Go to a truck stop with scales (Love's, etc) and have them weigh the coach for you. With the axel weight you can then refer to the pressure chart from your tire manufacturer to get the proper amount of air.

The max psi in my tires is 110lbs and I run mine at 85-90 psi per the chart for my tires and MH weight.

Terry

Our DSDP came with a 12,000# front axle and 275/70 22.5's According to the charts I needed 125 psi in the front Michelins. Newmar had Spartan replace the front axle with a 14,600# unit. At the same time they replaced the front wheels but not the tires. Then the gave me a letter on Michelin letterhead allowing the tires to be rated at the 125 psi rating with 120 psi in them as that was the max even the heavy duty rims would take. Ran them that way for 6 years or so with no problems. Have now replaced the front tires with 305/70's on Alcoa wheels.

And again, the pressure on the sidewall of a truck size tire is NOT the maximum that tire should ever have, it is the minimum to support the maximum rating of that tire.

JFXG 01-15-2014 09:11 PM

Your '07 will be a few thousand lbs heavier than my '02, and that difference will mostly be in the front axle. I have 19K rear axle and 12K front; you have 20K rear and (I think) 14.2K or 14.4K front. You'll probably need about 110-115lbs in the front (depending on tire size) and about 90-95lbs rear. Get weighed and set the proper pressure.

You'll have a hard time getting 110lbs into the fronts with the onboard compressor, and even 90lbs in the rears will be a slow pita. Onboard compressor relieves at 120psi, and cuts in again at 90psi. I tap danced with the onboard compressor for a year, and finally bit the bullet and bought a 150psi compressor from HF ($100 on sale). It lives in the small bay just forward of my batteries, and comes in handy for other things, too.

JG

vonkamp 01-16-2014 06:43 AM

If you have one of those cheap plastic coiled hoses, I would throw it out and get a nice 3/8 or 1/2 dia. 50' rubber compressor hose. The big box stores should sell them. The extra volume will move more air quicker...
Cheers,
Baron

Tireman9 01-16-2014 08:16 AM

Quote:

Originally Posted by Mr_D (Post 1885991)

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


I can't find the TOYO document you are quoting.

Tireman9 01-16-2014 08:18 AM

Quote:

Originally Posted by THERAPY GUY (Post 1885229)
Vehicle is a 2007 40' Dutch Star. 400 Cummins. I have tried to inflate the front tires to the 120 psi advised and find that the onboard compressor does not seem to put out that volume when I connect to the air chuck. I have to carry a separate pancake compressor that will do the job. Is there any way to increase the air out put on the coach or is there a secret to achieving the objective that I haven't learned yet. Suggestions welcome.
Thanks

Where did you get the instruction to inflate your fronts to 120 psi?

Is that the inflation shown on the tire Placard? or are you just reading the information on the tire about the Max cold pressure?

Sky_Boss 01-16-2014 09:06 AM

Actually, regarding onboard compressor...if I understood my Spartan Owner training, you can increase the traditional 120 PSI pressure in the tanks by adjusting the governor. I am verifying this and will get back to you on that.

FWIW, my front wheels need a minimum of about 112 PSI when running at the rated 14,600# axle rating. For some that means after adding 5 PSI for safety I am at 117 PSI. That would be a bit of a challenge for the on board set at 120 PSI.

To be honest I have never used my onboard system and judging from the condition of the chuck, neither did the previous owners. My 150 PSI Sears compressor meets my needs. It is a bit noisier than I like but running the engine isn't that much better.

A good chuck with a clip to hold the chuck on the valve stem, built in pressure gauge, with both and air up and air dump system is the way to go. Keeps the knees and back happy too.

POWERTANK - CO2 Air Systems

Sky_Boss 01-16-2014 12:28 PM

From Mike O'niel @ Spartan

Yes the governor is adjustable. Setting it to 130 psi cutout is where we set the governor on current production. When you change the cut out pressure it also changes the cut in. The governor has about 25 psi differential between cut out and cut in built into it. This does not mean you will get more pressure into your tires. The volume of the compressor will not overcome the volume in the tires by setting the pressure higher. You will get approximately 95 psi and maybe 100 psi to the tires. This will get enough air into the tires to safely drive to a high volume air source.

Your governor setting at 120psi cut out will give you a cut in at approximately 95 psi. The cut out at 130psi will bring the cut in to 105 psi.


All times are GMT -6. The time now is 07:19 AM.

Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2021, vBulletin Solutions, Inc.