Go Back   iRV2 Forums > MOTORHOME FORUMS > Class A Motorhome Discussions
Click Here to Login
Join iRV2 Today

Mission Statement: Supporting thoughtful exchange of knowledge, values and experience among RV enthusiasts.
Reply
  This discussion is proudly sponsored by:
Please support our sponsors and let them know you heard about their products on iRV2
 
Thread Tools Search this Thread Display Modes
 
Old 05-30-2015, 09:39 AM   #15
Senior Member
 
Join Date: Dec 2013
Location: Plantation, Fl
Posts: 1,068
Quote:
Originally Posted by Sky Pilot View Post


The reason I asked this question was to get an idea of how far off from Mfg recommendations people were getting when the weighed each corner of their coach. I don't think I saw any huge differences posted and did anyone, who has weighed their coach find they had to put substantially MORE psi in their tires than was on the Mfg placard? That was my main concern and I got some good info and thanks again.

Scott
If after weighing your RV, it calls for more psi than what's on the Mfg placard, chances are you have exceeded the load limits of the tires, or axles. I believe most builders suggest running pressures that support the weight of a maxed out axle.
As an example, consider the latest E450s in Class Cs. They have a 5,000# rated front axle, many builders suggest running the usual 225/75 tires at 75# psi, which according to Michelin and other tire charts, is enough to support 5,120#. The rear axles are rated at 9,600#, and many builders suggest running at 80psi (the max psi for that tire) which according to the charts supports 9,880#.
Lowering the tire pressures on your front tires, if possible, depending on the weights involved, could improve the ride and handling. The rears probably not as much of an affect.
In your case it might be interesting to have your RV weighed, particularly when you are (literally) carrying rocks.
__________________

__________________
2014 Itasca Spirit 31K
2016 Mazda CX5, on an Acme tow dolly, 4 trips 5800mi
Now 2017 RWD F 150 with a drive shaft disconnect
Mich F is online now   Reply With Quote
Join the #1 RV Forum Today - It's Totally Free!

iRV2.com RV Community - Are you about to start a new improvement on your RV or need some help with some maintenance? Do you need advice on what products to buy? Or maybe you can give others some advice? No matter where you fit in you'll find that iRV2 is a great community to join. Best of all it's totally FREE!

You are currently viewing our boards as a guest so you have limited access to our community. Please take the time to register and you will gain a lot of great new features including; the ability to participate in discussions, network with other RV owners, see fewer ads, upload photographs, create an RV blog, send private messages and so much, much more!

Old 05-30-2015, 09:41 AM   #16
Senior Member
 
DMTTRANSPORT's Avatar
 
Join Date: May 2014
Location: Henderson, Nevada
Posts: 1,225
Quote:
Originally Posted by brian-nicola View Post
Set it for the max weight less say 5-10% and forget it. You don't see L/H truckers changing their pressures every time the load changes or when they are bob tailing. I might get flamed, but I think too many people over think this issue on tire pressures.
What He/She said
__________________

__________________
2005 Newmar DS 4023, Spartan Chassis, ISL 370 Cumapart, 2008 Jeep Rubicon 4dr, 2015 Kia Soul, 1969 Italian & 2004 Akita
DMTTRANSPORT is offline   Reply With Quote
Old 05-30-2015, 10:03 AM   #17
Senior Member
 
brian-nicola's Avatar


 
Fleetwood Owners Club
Join Date: Sep 2012
Location: Vancouver Island, BC
Posts: 817
Click image for larger version

Name:	IMG_0925.JPG
Views:	69
Size:	705.9 KB
ID:	95644Yes Scott, that is what they do. Max axle weight with corresponding tire pressure for the load, my spreadsheet is like this;


MAX GVW FRONT 120PSI 12400# (as per placard)
ACTUAL FRONT WEIGHT 110PSI 11465# (psi taken from tire mfg)
RESIDUAL 935#

MAX GVW REAR 105PSI 21000#
ACTUAL REAR WEIGHT 100 PSI 20685#
RESIDUAL 315#
Attached Thumbnails
Click image for larger version

Name:	IMG_0923.JPG
Views:	53
Size:	515.6 KB
ID:	95645  
__________________
Brian & Nicola
2013 Discovery 40E "DISCO"
TOAD 2014 Wrangler
Xeena(German Shepard)
brian-nicola is offline   Reply With Quote
Old 05-30-2015, 10:37 AM   #18
Senior Member
 
Join Date: Dec 2013
Location: Plantation, Fl
Posts: 1,068
Quote:
Originally Posted by brian-nicola View Post
Set it for the max weight less say 5-10% and forget it. You don't see L/H truckers changing their pressures every time the load changes or when they are bob tailing. I might get flamed, but I think too many people over think this issue on tire pressures.
If someone is running near, at, or over their gross weight ratings (many people are), arbitrarily reducing psi 5-10%, would not be a good thing.
__________________
2014 Itasca Spirit 31K
2016 Mazda CX5, on an Acme tow dolly, 4 trips 5800mi
Now 2017 RWD F 150 with a drive shaft disconnect
Mich F is online now   Reply With Quote
Old 06-01-2015, 11:05 AM   #19
Senior Member
 
Rexhall Owners Group
Join Date: Jul 2014
Location: Auburndale, Florida
Posts: 190
Thumbs up

Quote:
Originally Posted by brian-nicola View Post
Set it for the max weight less say 5-10% and forget it. You don't see L/H truckers changing their pressures every time the load changes or when they are bob tailing. I might get flamed, but I think too many people over think this issue on tire pressures.
I agree!
__________________
Mick & Vonna, 1999 Rexhall Rexair
GRUU is offline   Reply With Quote
Old 06-01-2015, 11:25 AM   #20
Senior Member
 
ShapeShifter's Avatar


 
Monaco Owners Club
Holiday Rambler Owners Club
Join Date: Feb 2010
Location: Buffalo, NY
Posts: 1,632
Quote:
Originally Posted by brian-nicola View Post
You don't see L/H truckers changing their pressures every time the load changes or when they are bob tailing. I might get flamed, but I think too many people over think this issue on tire pressures.
Correct, they assume max load all of the time. If they are running light, they generally aren't worried about the extra hard tires banging over bumps and jarring the empty trailer, nor are they that worried about the cab being jarred: their cab is isolated from the frame, and most of them have an air suspension in their seats to give them a soft comfortable ride.

On the other hand, our motorhome bodies are not isolated from the frame, nor do we have air suspension seats. Any jarring over bumps caused by over inflated tires are transmitted directly to the coach contents and to our butts and backs. If you want a comfortable ride, tire pressure is more important than with a truck. If you don't care at all about ride comfort, then go right ahead and use full pressure on the tires.

You're comparing apples to oranges: different vehicle construction, different usage profiles, and different ride expectations.

Quote:
Originally Posted by Rich-n-Linda View Post
When we bought our coach, the former owner was doing what you are doing, running the maximum allowed pressure - 120 psi - in all the tires.
No, that is not the MAXIMUM allowed pressure! Read your tire carefully: It is the MINIMUM required pressure to achieve the MAXIMUM weight carrying ability of the tire. There is a big difference! Confusion over this is very common.

Weight carrying ability is directly related to the pressure in the tires. If you want the tire to be able to carry its full rated weight, then you need to fill the tire to AT LEAST the pressure stamped on the tire sidewall. That number is not the maximum inflation limit! That MINIMUM pressure stamped on the sidewall will give you the best possible weight carrying capacity, but it will not necessarily give you the best handling, ride, or tire life.

If you are actually carrying less weight on the tire, you can safely reduce the tire pressure in many cases, and that can have a positive effect on ride comfort, handling, and tire life.
__________________
Adam and Sue, and a pack of little furballs
2007 Holiday Rambler Endeavor 40PDQ Limited Edition - Cummins ISL 400
2013 Ford F-150 FX4 toad - USGear Unified Tow Brake, Roadmaster Blackhawk II Tow bar, Blue Ox baseplate
Home base near Buffalo NY, often on the road to a dog show
ShapeShifter is offline   Reply With Quote
Old 06-01-2015, 11:53 AM   #21
Senior Member
 
Mr_D's Avatar
 
Solo Rvers Club
iRV2 No Limits Club
Join Date: May 2011
Location: Vancouver, WA
Posts: 28,423
Quote:
Originally Posted by Sky Pilot View Post
I have owned 6 or 7 Motorhomes and have never weighed them and always kept the recommended pressure in the recommended tires. I have never had an issue with the tires. The only blowout was in a friends coach that I was slow transporting for him for a free coast to coast 3 week vacation and he had just had it serviced and I did not check tire pressure as assumed the dealer did.

For those of you who weigh your coaches, how much difference have you found between the recommended tire pressure and the pressure that you end up putting into them? And did it make any noticeable difference in the ride?

Thanks
If you have never weighed the rig how do you know the "recommended pressure"?
If you're going by the weight sticker in your rig then, in most cases, that's only if the rig weighs it's legal maximum.
But in some, like our Magna, CC says to run the weight sticker pressure at all times.
__________________
2009 45' Magna 630 w/Cummins ISX 650 HP/1950 Lbs Ft
Charter Good Sam Lifetime Member, FMCA, SKP
RV'ing since 1957, NRA Benefactor Life, towing '14 CR-V
Mr_D is offline   Reply With Quote
Old 06-02-2015, 09:03 AM   #22
Senior Member
 
Join Date: Apr 2015
Location: Tampa Bay area
Posts: 105
As a final update: I had bought this coach to make an emergency trip with an elderly relative, I did not have much time to check everything out but did do a test drive on a local interstate and found a lot of wander and some vibration in the steering wheel. I was able in a day to add a Safe T Plus stablizer, which should be standard equipment from Mfg imo and took the coach to a shop to have the new tires rebalanced.

The tire shop found a lot of powder someone used to try and the balance tires and in one of the front tires that powder had gotten wet and balled up into a clump causing the vibration. Since it was a commercial tire shop that does a lot of Motorhomes, I assumed they put the proper pressure in the tires and had to load the coach and leave early the next a.m. without checking pressure.

The steering was now fine and I could take my hands off the wheel for 5 to 10 secs on a straight road and it traveled straight as an arrow thanks to the Safe T Plus but the coach really rode rough and was very noisy on some of the bad interstates, but I was in a hurry and traveled 840 miles in a day. Upon arriving at my destination, I checked tire pressure and found the dealer had installed 100-105# in the rears when the Mfg recommendation was 85.

I put 85# in the rears, the fronts were set properly at 95 and I headed home with the cargo bays full of items I brought back. I had at least a 1000# more on the return trip than the outbound trip and it was scattered out in various bays, with size of the bay dictating which side the heavy items were placed on.

The coach rode and handled 200% better on the way home and was 400% quieter as I was not riding on rear tires that seemed like solid rubber. This is typical (big differences in weights and loads per side) of how I use my coach and why I do not see the logic in my case of weighing it since I seldom carry the same load. For those of you that travel with a standard load much of the time, I see it making a lot of sense.

Thanks for all the good advice.

Scott
__________________

__________________
Sky Pilot is offline   Reply With Quote
Reply

Tags
tire pressure



Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Country Coach or American Coach or Alpine Coach Troys66 Class A Motorhome Discussions 14 01-04-2015 07:38 PM
Low oil pressure | erratic oil pressure | inconsistant oil pressure GlennLever Cummins Engines 45 08-28-2014 09:24 AM
Coach Net - You decide OSP1268 iRV2.com General Discussion 5 06-01-2014 11:19 AM
The Entegra Coach Connection DriVer RV Industry Press 0 05-16-2014 08:00 PM
RV of the Year Awarded to Thor Motor Coach Class A RUV Motorhomes DriVer RV Industry Press 0 12-12-2013 01:00 PM

» Virginia Campgrounds

Reviews provided by


Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -6. The time now is 09:13 AM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.