RV.Net Open Roads Forum: Class A Motorhomes: Figuring the correct tire pressure

RV Blog

  |  

RV Sales

  |  

Campgrounds

  |  

RV Parks

  |  

RV Club

  |  

RV Buyers Guide

  |  

Roadside Assistance

  |  

Extended Service Plan

  |  

RV Travel Assistance

  |  

RV Credit Card

  |  

RV Loans

Open Roads Forum Already a member? Login here.   If not, Register Today!  |  Help

Newest  |  Active  |  Popular  |  RVing FAQ Forum Rules  |  Forum Help and Support  |  Contact  

Search:   Advanced Search

Search only in Class A Motorhomes

Open Roads Forum  >  Class A Motorhomes  >  Maintenance Issues & Tips

 > Figuring the correct tire pressure

Reply to Topic  |  Subscribe  |  Print Topic  |  Post New Topic  | 
Sponsored By:
two travelers

Smithtown, NY

Senior Member

Joined: 07/27/2004

View Profile


Offline
Posted: 02/16/17 01:54pm Link  |  Quote  |  Print  |  Notify Moderator

Recently had our coach weighed. We are at 6,700 lbs (3350 per tire) front and 12,180 lbs (3350 per tire) rear when fully loaded. Tires are Goodyear G670. Using the tire pressure chart from Goodyear it would appear that 80 lbs psi is what we want. At that inflation, the steer axle weight is 3640 lbs and rear at 3415 lbs. Tire inflation chart on coach shows 92 lbs psi. It rides like its on hard rubber tires. Should I use the 80psi or bump it up a few lbs? Thanks to all who share their knowledge!!

Effy

NC

Senior Member

Joined: 07/26/2011

View Profile



Posted: 02/16/17 02:13pm Link  |  Quote  |  Print  |  Notify Moderator

Confused, are you saying that after you set the PSI, you weighed it again and the weight per wheel changed? You claim your weight in the front increased almost 300 per wheel and 65 in the rear. So your MH gained weight??? I am lost.


2013 ACE 29.2


wildtoad

Blythewood, SC

Senior Member

Joined: 06/05/2011

View Profile



Good Sam RV Club Member

Offline
Posted: 02/16/17 03:20pm Link  |  Quote  |  Print  |  Notify Moderator

Set them at 80 and see if you like the ride. Based on your info 80 will support more than you weigh.


Tom Wilds
Blythewood, SC
2016 Newmar Baystar Sport 3004

dalenoel

S.E. Michigan

Senior Member

Joined: 09/03/2007

View Profile





Offline
Posted: 02/16/17 03:27pm Link  |  Quote  |  Print  |  Notify Moderator

At the 80psi inflation you are able to handle more weight than what the axle actually has. What you don't know is if the weight on the curb side is the same as the street side. The best route is to weight each corner and use the heaviest weight for each side of the axle as the weight for both tires on that axle.

Since you don't know the actual 4 corner weight your estimate is better in having more weight carrying capacity that the actual average. In other words 7280 for the front axle and 13660 for the rear axle. This does give you a little margin for some error in calculation.

Less pressure will, or should, give you a little better ride but you don't want to go too low until you know the heaviest corner and end up under the recommended pressure.


03 Monaco 36PBD DP - 06 Malibu Maxx Toad
08 Jayco Eagle 322FKS (SOLD)
Wife and myself, Lutheran Deacon, Oreo the Malshi, and maybe a grandkid or two
Tracking campgrounds with Ultimate Campground Log


theoldwizard1

SE MI

Senior Member

Joined: 09/07/2010

View Profile


Offline
Posted: 02/17/17 09:40am Link  |  Quote  |  Print  |  Notify Moderator

What is the maximum on the sidewall ?

I would use that. Less rolling resistance (might help fuel economy). Less sidewall flex (reduces heat and stress on the tire).

wildmanbaker

Kennewick, Washington

Senior Member

Joined: 02/24/2005

View Profile






Posted: 02/17/17 11:40am Link  |  Quote  |  Print  |  Notify Moderator

theoldwizard1 wrote:

What is the maximum on the sidewall ?

I would use that. Less rolling resistance (might help fuel economy). Less sidewall flex (reduces heat and stress on the tire).
Yes, don't trade comfort for safety. If you have tried the manufacture's recommendations and don't like it try 5 psi more to see of the drive is better. Low tire pressure, flexing, and heat buildup are killers for the tires.


Wildmanbaker


Jim Norman

NJ

Senior Member

Joined: 03/29/2009

View Profile



Good Sam RV Club Member

Offline
Posted: 02/17/17 06:46pm Link  |  Quote  |  Print  |  Notify Moderator

Just right is what you really want, however it is difficult to obtain. You need a 4 corner weigh, then set your pressures to the heavier corner for the front and for the rear. Under inflation is a killer, in many ways. Tires overheat, sidewalls flex way beyond design, handling downgrades and ride can worsen. Now over inflating has its own issues, hard ride, odd tread wear among others.

So get weighed with your rig as full as you use it, not empty. Get each corner weighed and then do the research. And when you are done, remember tire pressure is not a constant! Monitor it! If you inflate in June, you will not be correct in December! Check you tire pressure each trip, or possibly get a TPMS system and set it up. It could save more than a flat tire.


2016 Tiffin Allegro Red 38QBA
2008 Jeep Liberty (aka FireToad)


Ductape

On the Road

Senior Member

Joined: 11/15/2005

View Profile


Offline
Posted: 02/17/17 06:59pm Link  |  Quote  |  Print  |  Notify Moderator

Your analysis is correct. As always you'll get a bunch of wildly conflicting opinions on the internet. Trust Goodyear, they do this for a living.


49 States, 6 Provinces, 2 Territories...

Dale.Traveling

Newport News, VA

Senior Member

Joined: 12/16/2010

View Profile



Good Sam RV Club Member


Posted: 02/17/17 07:49pm Link  |  Quote  |  Print  |  Notify Moderator

Go with the what Goodyear recommends but also add a few PSI to compensate for potential increases in loading or temperature changes.

The coach chart is based on the listed size and load class of the tires that were installed by the chassis builder. If the tires you have now does not match what is listed the chart numbers should not be used.

If you cross reference the chart numbers you'll find the pressure listed for the tire listed will be slightly over the axle maximum capacity. In other words the chart is the pressure for the tires listed if you load the coach to the axle maximum. If your current weight is less than chassis maximum that would be the reason why the pressures don't match and why your ride is rather harsh.

Also if you're off the bottom of the chart, as I am, don't try and extrapolate what the pressure could be. Best to stay at or above the minimum pressure listed on the OEM chart.

* This post was edited 02/17/17 07:57pm by Dale.Traveling *


2006 Hurricane 31D aka 'Moby' the Whale
FCC(SW) US Navy Retired 1980-2003
Stella my Navigator
Bogart the All American RV Dog
and
Cocoui and Hanna waiting for me at the Rainbow Bridge


Jim Norman

NJ

Senior Member

Joined: 03/29/2009

View Profile



Good Sam RV Club Member

Offline
Posted: 02/18/17 11:54am Link  |  Quote  |  Print  |  Notify Moderator

I'll second that! NEVER GO BELOW THE MINIMUM. A tire needs a certain inflation to maintain its integrity.

Reply to Topic  |  Subscribe  |  Print Topic  |  Post New Topic  | 

Open Roads Forum  >  Class A Motorhomes  >  Maintenance Issues & Tips

 > Figuring the correct tire pressure
Search:   Advanced Search

Search only in Class A Motorhomes


New posts No new posts
Closed, new posts Closed, no new posts
Moved, new posts Moved, no new posts

Adjust text size:

© 2017 CWI, Inc. © 2017 Good Sam Enterprises, LLC. All Rights Reserved. | Terms of Use | PRIVACY POLICY | YOUR PRIVACY RIGHTS