Reply
 
Thread Tools Search this Thread Display Modes
 
Old 08-05-2014, 11:10 AM   #1
Rivet Master
Commercial Member
 
ViewRVs's Avatar
 
1977 20' Argosy 20
Charleston , West Virginia
Join Date: Feb 2002
Posts: 1,226
Images: 9
Send a message via Yahoo to ViewRVs
Rear tire pressure?

I am currently running 40 psi in my rear tires per the manual. I recently saw that the chassis came from the factory with 55 psi in the rear. I am concerned that the 40 psi is hurting my gas mileage. I have been running between 7 and 9.5 MPG in my Argosy 20 after the carb rebuild. Before that, it was around 8 MPG.

What psi are you guys putting in the rear tires?

(I am running with the factory 70 psi in the front tires.)
__________________

__________________
Fred H.
1977 Argosy 20' Motorhome
Fred's Airstream Archives @ ViewRVs.com
ViewRVs is offline   Reply With Quote
Old 08-05-2014, 02:14 PM   #2
4 Rivet Member
 
mprokop87's Avatar
 
1976 24' Argosy 24
Victor , New York
Join Date: Sep 2012
Posts: 377
Im running 55-ish psi and I wish my mileage was that good! I just did some work on my carb so I guess we will see on the next trip.
__________________

__________________
mprokop87 is offline   Reply With Quote
Old 08-05-2014, 02:42 PM   #3
Rivet Master
 
HowieE's Avatar
 
1991 34' Excella
Princeton , New Jersey
Join Date: Aug 2003
Posts: 6,811
Images: 12
Tire pressure is a function of the load on the tires not what is printed on the tire as max nor what is in the manual.

After weighing your rig look on the tire inflation chart and see the recommended tire pressure.

http://www.goodyearrvtires.com/pdfs/rv_inflation.pdf

Note that dual tires run at a lower pressure than singles.

The chart is good for any manufacture as the government require that tires of a given size all meet the same specs.

If your tires are not on this chart look for the Michelin RV tire inflation chart.
__________________
WBCCI 12156 AIR 3144 WACHUNG TAC NJ6
2004 Excursion 4x4
1991 34 ft. Excella +220,000 miles, new laminated flooring, new upholstery, new 3200 lbs axles

HowieE is online now   Reply With Quote
Old 08-06-2014, 05:33 AM   #4
2 Rivet Member
 
Berkel-Enschot , Noord-Brabant
Join Date: Apr 2014
Posts: 30
You better use my made pressure/loadcapacity lists, they take better care of giving the same deflection of tire over the whole range of Pressure/loadcapacity.

https://onedrive.live.com/?cid=A526E...E092E6DC%21904

First open the USA map with given in PSI and LBS.
then you can choose the submap for if you want it given per tire, axle single or axle dual, I would take the axle single , so you dont need to devide the axle loads by 2 anymore.

then first determine the reference-pressure(Pr)/Atpressure/maxloadpressure/pressure needed for the maximum load up to 160km/99m/h, wich is not the maximum pressure of tire.
If we are talking about your 70 psi in front tires, I think you have E-load tires with Pr/// of 80 psi or mayby D-load with exeption 70 psi Pr/// instead of the usual 65 psi.
Then download or leftclick the PDF beginning with the Pr.
In that list first search the Loadindex/maximum load in the first rows then in that line the load you want to know it for, and look above or below it for the needed pressure.
Always first add a 10% extra to the load before looking it up in the list.
The car-makers use nowadays the GAWR's to fill in for normal use , American pressure stickers only give that advice. But sometimes for heavy duty maximum load of tire is used or even maximum pressure of tire , wich gives terrible bumping when normally loaded.
The difference in gas- milage between this determined pressure and high pressure is not that big, but enaugh and not to high pressure gives better comfort and gripp, and less nervous stearing when on front.
__________________
jadatis is offline   Reply With Quote
Old 08-07-2014, 05:23 AM   #5
CapriRacer
 
CapriRacer's Avatar
 
I'm in the , US
Join Date: Sep 2012
Posts: 624
Quote:
Originally Posted by ViewRVs View Post
I am currently running 40 psi in my rear tires per the manual. I recently saw that the chassis came from the factory with 55 psi in the rear. I am concerned that the 40 psi is hurting my gas mileage. I have been running between 7 and 9.5 MPG in my Argosy 20 after the carb rebuild. Before that, it was around 8 MPG.

What psi are you guys putting in the rear tires?

(I am running with the factory 70 psi in the front tires.)
This doesn't sound right. Are you sure your manual says 70 psi front/40 psi rear?

What about the vehicle tire placard? What does it say? It ought to be the same as the manual. The placard be on the driver's doorframe (if you have a 2008 and newer model, but may be elsewhere if older.)
__________________
CapriRacer is offline   Reply With Quote
Old 08-07-2014, 02:18 PM   #6
Rivet Master
Commercial Member
 
ViewRVs's Avatar
 
1977 20' Argosy 20
Charleston , West Virginia
Join Date: Feb 2002
Posts: 1,226
Images: 9
Send a message via Yahoo to ViewRVs
Quote:
Originally Posted by CapriRacer View Post
The placard be on the driver's doorframe (if you have a 2008 and newer model, but may be elsewhere if older.)
..... except that this is the Argosy motorhome forum and my vehicle is a 1977 Argosy 20 MH on a Chevy P-30 truck chassis.
__________________
Fred H.
1977 Argosy 20' Motorhome
Fred's Airstream Archives @ ViewRVs.com
ViewRVs is offline   Reply With Quote
Old 08-07-2014, 08:28 PM   #7
Rivet Master
Commercial Member
 
ViewRVs's Avatar
 
1977 20' Argosy 20
Charleston , West Virginia
Join Date: Feb 2002
Posts: 1,226
Images: 9
Send a message via Yahoo to ViewRVs
Here is a picture of the page from my manual showing 70 psi up front and 40 psi in the rear.
Attached Thumbnails
Click image for larger version

Name:	IMG_20140807_210416565_HDR.jpg
Views:	61
Size:	82.0 KB
ID:	218559  
__________________
Fred H.
1977 Argosy 20' Motorhome
Fred's Airstream Archives @ ViewRVs.com
ViewRVs is offline   Reply With Quote
Old 08-07-2014, 09:42 PM   #8
Rivet Master
 
Smartstream's Avatar

 
1982 28' Airstream 280
Port Angeles , Washington
Join Date: Aug 2008
Posts: 1,371
Without knowing your actual weight that agrees with the P-30 manual from GM. I believe it is somewhere here on the forum. I have a pdf of it but can't copy the page.
__________________
Cheers, Dan
________________________________________


"Socialist governments traditionally do make a financial mess. They always run out of other people's money. It's quite a characteristic of them."
~ Margaret Thatcher ~
Smartstream is offline   Reply With Quote
Old 08-08-2014, 06:12 AM   #9
CapriRacer
 
CapriRacer's Avatar
 
I'm in the , US
Join Date: Sep 2012
Posts: 624
Quote:
Originally Posted by ViewRVs View Post
Here is a picture of the page from my manual showing 70 psi up front and 40 psi in the rear.
Good. That seems very clear.

And just to dot the i's and cross the t's, you are using 8.75-16.5's right? That would be bias ply tires. If you are using radials, you'll want 5 psi more.

And considering how long ago the manual was written, it would be advisable to use even more. say 10 psi at both ends.

But if you aren't using the 8.75-16.5's, then we have a whole bunch of recalculation to do.
__________________
CapriRacer is offline   Reply With Quote
Old 08-09-2014, 01:47 PM   #10
2 Rivet Member
 
Berkel-Enschot , Noord-Brabant
Join Date: Apr 2014
Posts: 30
Is the back by any chanche dual so 4 tires on the ( imaginary) axle?
That would explain the low advice pressure , because rear GAWR is mostly more then front.

Then if the advice is for bias ply , those are calculated in their loadcapacity with a formula that gives almost 70% of maximum load at 50% of AT-pressure.

To get a right advice for radial ( if you have those) I need GAWR's and maximum load and AT-pressure of tires at least.
GVWR and speedcode of tires would be nice too.
And ofcource even better axle or better 4 point weighing in loading you drive with.
__________________

__________________
jadatis is offline   Reply With Quote
Reply


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
High Pressure vs. Low pressure Appliances emenriquez General Appliance Topics 2 06-15-2009 02:04 AM
Tire Pressure Gauges- Pressure Varies! Ray Eklund Tires 14 07-06-2008 09:34 AM
Canadian Tire's $129 Tire Pressure Monitoring System SilverCottage Tires 9 10-30-2007 08:55 PM
Low pressure / High pressure appliances Rick LP Gas, Piping, Tanks & Regulators 1 06-15-2002 07:29 PM
Tire Pressure thenewkid64 Tires 1 03-31-2002 02:44 PM


Virginia Campgrounds

Reviews provided by




Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -6. The time now is 02:23 PM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.

Airstream is a registered trademark of Airstream Inc. All rights reserved. Airstream trademark used under license to Social Knowledge LLC.