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04-26-2018, 04:40 PM
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#1
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Member
Join Date: Jun 2017
Posts: 77
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Tir pressure.
I have a 36 foot pace arrow.
It has 19.5 inch tires. single axil with dual tires.
Looking for a starting pressue setting wihout any weight measurements. Tires are rated for 120 psi. Thinking of starting with 100 psi.
Any input is appriceated. Hope to get weighed on next trip.
Thanks.
__________________
Ron and Regina
2002 36R Pace Arrow
Toad saturn on tow dolly
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04-26-2018, 04:49 PM
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#2
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Senior Member
Commercial Member
Join Date: Mar 2010
Location: Akron, Ohio
Posts: 2,781
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Quote:
Originally Posted by Macbow
I have a 36 foot pace arrow.
It has 19.5 inch tires. single axil with dual tires.
Looking for a starting pressue setting wihout any weight measurements. Tires are rated for 120 psi. Thinking of starting with 100 psi.
Any input is appriceated. Hope to get weighed on next trip.
Thanks.
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What pressure is shown on the certification label? That is a good starting point till you at least get truck scale axle numbers.
Did you bother to do a search on "air pressure" There are a few newer posts that cover how to learn the proper inflation for RV tire application.
__________________
Retired Design & Quality Tire Eng. 40+ years experience. Recognized in the industry and in court as an expert in failed tire inspection as I have performed thousands of failed tire "autopsies".
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04-27-2018, 08:19 AM
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#3
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Senior Member
Join Date: Sep 2014
Location: Poulsbo, WA
Posts: 749
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Until you get weighed, use the axle weights provided by coach manufacturer, then look up the recommended pressures based on tire manufacturer and size of tires. The maybe add a few extra pounds.
Seems on our previous 34' Bounder on 19" wheels I kept pressures around 90 front and rear.
__________________
Bill and Debb---2010 CT Coachworks Siena 35V
1999 Jeep Cherokee Sport---Roadmaster Falcon 5250 -
1 Cavalon (Scooby) 1 Papipoo (Bella- DOB 5/06/18)
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04-27-2018, 08:32 AM
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#4
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Member
Join Date: Jun 2017
Posts: 77
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Thanks the recommended pressure on the chasis info is 85 psi.
The new tires are rated at 120 psi.
I’ll also do another search.
__________________
Ron and Regina
2002 36R Pace Arrow
Toad saturn on tow dolly
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04-27-2018, 10:57 AM
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#5
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Senior Member
Join Date: Nov 2012
Location: bis. nd
Posts: 1,124
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i do mine by math.. the tire holds x amount of weight. the air pressure is y. so if 120 psi at 7000#'s then you do the math to get psi per pound of weight.. then use that to air your tires say 6000 #'s and the pse per pund to get the result.. ...of course fronts are different than rears and if duals same math..
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2007 Alfa Gold!! model 1008. 400hp Freightliner, IFS!!
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04-27-2018, 01:34 PM
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#6
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"Formerly Diplomat Don"
Newmar Owners Club
Join Date: Apr 2005
Location: Moorpark, Ca.
Posts: 23,931
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If the recommended pressure by the coach manufacturer is 85, I would safely set it at 90 until you get the coach weighed. Check locally, often places like rental yards have scales that you can at least get axle weights.
As soon as you get the weights, you can set the pressure, so you can get your smoothest ride.
__________________
Don & Mary
2019 Newmar Dutch Star 4018 (Freightliner)
2019 Ford Raptor
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04-27-2018, 04:23 PM
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#7
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Senior Member
Fleetwood Owners Club American Coach Owners Club
Join Date: Mar 2011
Posts: 6,760
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Weigh the coach, get axle weight, use the heavy side for the base weight for both sides, look up the desired pressure for that weight in the tire manufacturer's manual and add 10%. No guessing.
__________________
2014 American Eagle 45T
DD 13, 500 HP
Pulling a Honda CRV
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04-27-2018, 04:36 PM
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#8
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Senior Member
Join Date: Oct 2012
Posts: 825
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Find Gawr's and add 10% to those.
Then read from sidewall maxload and determine AT wich pressure( already gave 120 psi).
Then calc lineair so gawr+10%/ 2x maxload of tire X 120 psi.
Then you sertanly wont haveto low pressure, if you dont overload,
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04-27-2018, 04:56 PM
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#9
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Senior Member
Commercial Member
Join Date: Mar 2010
Location: Akron, Ohio
Posts: 2,781
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Quote:
Originally Posted by beenthere
i do mine by math.. the tire holds x amount of weight. the air pressure is y. so if 120 psi at 7000#'s then you do the math to get psi per pound of weight.. then use that to air your tires say 6000 #'s and the pse per pund to get the result.. ...of course fronts are different than rears and if duals same math..
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Have you compared the results of your math to the published Load & Inflation tables for 3 or 4 different size tires? You may be surprised with your results.
__________________
Retired Design & Quality Tire Eng. 40+ years experience. Recognized in the industry and in court as an expert in failed tire inspection as I have performed thousands of failed tire "autopsies".
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04-27-2018, 05:27 PM
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#10
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Senior Member
Join Date: Jul 2010
Posts: 5,314
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The simple step process.
If you know nothing use the tire pressure as stated on the tire.
If you have the PSI info from RV manufacturer and nothing else, use it.
If you know your actual weights use the tire manufacturers chart values. Some add a fudge/safety percentage.
Don’t overthink this.
__________________
Tom
2016 Newmar Bay Star Sport 3004
2021 Jeep Gladiator Sport Willys
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04-27-2018, 06:16 PM
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#11
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Member
Join Date: Jun 2017
Posts: 77
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Thanks all, at least have a starting point till I can weigh.
__________________
Ron and Regina
2002 36R Pace Arrow
Toad saturn on tow dolly
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04-28-2018, 01:06 PM
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#12
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Senior Member
Join Date: Oct 2012
Posts: 825
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Quote:
Originally Posted by jadatis
Find Gawr's and add 10% to those.
Then read from sidewall maxload and determine AT wich pressure( already gave 120 psi).
Then calc lineair so gawr+10%/ 2x maxload of tire X 120 psi.
Then you sertanly wont haveto low pressure, if you dont overload,
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I overreax that you have dual load axle in rear so for rear formula
GWAR+10%/ 4x maxload dual x 120 psi.
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04-28-2018, 01:14 PM
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#13
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Senior Member
Join Date: Nov 2012
Location: bis. nd
Posts: 1,124
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i did for my tire size and used couple different manufacturers pages. And so close {usually psi couple pounds higher..
heres my tire General HS 295/75r22.5
6940#'s at 120 psi.. equals 57.83333 #'s per psi
so say i have 5500#'s on tire then 5500 divided by 57.8333 equals 95+ psi so i put 96 psi in tire. if you want check like Michelin or others see how close.. and i check heat after 100 or so miles on both sides cause sun side on hot days always little warmer and more and maybe 1-3 psi differentpsi.. and its how guy trained me OTR in 1980+..
Quote:
Originally Posted by Tireman9
Have you compared the results of your math to the published Load & Inflation tables for 3 or 4 different size tires? You may be surprised with your results.
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__________________
2007 Alfa Gold!! model 1008. 400hp Freightliner, IFS!!
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04-28-2018, 08:30 PM
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#14
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Senior Member
Join Date: Sep 2009
Posts: 1,536
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How it’s supposed to work.
You should know that the vehicle manufacturer/final stage certifier sets the recommended cold inflation pressures. Those recommendations are minimum and inflation pressures should never be below those recommendations. That’s a tire industry standard.
Inflation pressure adjustments between what has been recommended and tire sidewall/wheel max loads are optional. Normally done to correct an axle imbalance condition or a single tire overload condition. Never to exceed the vehicle’s GVWR.
The load capacity provided by the Original Equipment tires are your benchmark for all replacement tires of another size and load capacity. To do that you need an inflation chart for the OE tire size and the replacement tire size. You use the OE chart to determine how much load capacity is provided by the OE tires at the vehicle manufacturer’s recommended cold inflation pressures. Then you use the replacement tire’s inflation chart to set a recommended cold inflation pressure that, at the minimum, will provide a load capacity equal to the OE tires.
NHTSA allows the use of auxiliary tire placards for plus sized tires. It’s used to identify the new tire size and recommended inflation pressure and can by affixed near the original tire placard. Notes in the vehicle owner’s manual are also recommended.
You can read all about it in chapter #4 of the following reference.
https://www.ustires.org/sites/defaul...TruckTires.pdf
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