Tire Pressures

[keigm]

Greetings,  My wife and I recently purchased a 2014 Newmar Mountain Aire.  We moved up from our 27' HR Travel Trailer of 20 years.  I am now trying to get up to speed with the ins and outs of our new to us coach.  Due to conflicting information I need to know the correct tire pressure and hopefully why.  The front 2 tires are recommended to be at 125 psi and the back 6 are recommended to be 85 psi with the maximum of all 8 130 psi.  I have a friend with a similar coach who told me 85 was too little and he runs his at 110 psi.  Right now I have just split it down the middle and have the back 6 at 100.  I'd like to get some better clarification if I could.  Thank you in advance for your expertise.

 

[wolfe10]

Keigm,

Welcome to the FMCA Forum.

Indeed correct tire pressure can be confusing at first.

So, let's go through sources of information on correct tire pressure:

The GVWR (Gross Vehicle Weight Rating) sticker, usually located near the driver's seat area contains a lot of information including OE wheel size, tire size and recommended tire pressure IF EACH AXLE IS LOADED TO ITS GAWR (Gross Axle Weight Rating).  Therein lies the first rub-- is each axle at its weight rating, above or below???

The BEST way to determine correct tire pressure (actually what you are determining is correct MINIMUM tire pressure for a given weight) is to weight the individual wheel positions. Then go to your tire manufacturer's inflation table with the heavier wheel position on each axle.  Each tire on that axle to have the PSI based on the heavier wheel position. It is sometimes difficult to find a place to get individual wheel weights.  If you are going to the FMCA Convention in Chandler, AZ, RVSEF will be doing individual wheel weighting at the Convention. Again, this will give you the correct MINIMUM recommended PSI.  Most of us add 5-10 PSI to this minimum as long as it does not exceed the max of tire or wheel as a fudge factor, so that big shopping trip or a cold snap does not put you under the recommended PSI.

Next best is to weight each axle, which can be done at many truck stops, etc.  The rub is that you are ASSUMING perfect left/right weight distribution-- very unlikely.  So here you would need to add more of a "fudge factor".

Weighting will also tell you if your coach's weight is reasonably distributed.  With a tag axle, adjustment to ride height on the tag axle changes weight on both drive and front axle. Ideally each axle will carry the same PERCENT of its GAWR.  A good idea to have RIDE HEIGHT checked and tag axle loading adjusted before the weighing to determine correct minimum PSI.

[keigm]

Thank you Wolfe10 for the quick reply.  I probably won't be able to make the convention this year as all this has come about rather quickly.  Hopefully I can get it on the calendar for next year.  

[wayne77590]

Keigm,

It looks like you are in Albuquerque.  Here is a listing of truck stops that have scales: Albuquerque Weigh Stations

[wildebill308]

9 hours ago, Keigm said:

Thank you Wolfe10 for the quick reply.  I probably won't be able to make the convention this year as all this has come about rather quickly.  Hopefully I can get it on the calendar for next year.  

Chandler is next year March 7-10th and just a short run. The next International Convention is in Indianapolis, July 12-16, 2017.

There will be lots of how to seminars and training available.

Bill 

 

 

[keigm]

Thanks WILDEBILL

[keigm]

On 11/26/2016 at 1:03 PM, Wayne77590 said:

Keigm,

It looks like you are in Albuquerque.  Here is a listing of truck stops that have scales: Albuquerque Weigh Stations

Thanks!