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12-03-2012, 07:54 PM
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#1
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Community Moderator
Join Date: Sep 2011
Location: Between the Oceans
Posts: 8,034
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Help me set tire pressure
I just bought a set of TireMinder TPMS. To set it up correctly, I need to enter manufacturer's recommended tire pressures, so I called Country Coach tech support this afternoon. The rep asked me if I had it weighed, I told him not yet and inside pretty much empty; he then recommended 120psi for front and 115psi for rear.
I searched this forum, there were quite a number of threads on this topic. However the more I read the more I felt unsure if 120/115 is a little too high. most people were talking about 100psi.
What are the pressures on your wheels, on similar country coach 40 footers?
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Steven & Polly
2000 Country Coach Intrigue 40' ISC 350
2018 Ford Explorer 4WD
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12-03-2012, 08:12 PM
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#2
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Senior Member
Join Date: Dec 2006
Location: St. Augustine, FL
Posts: 3,595
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Sounds like you may be getting the cart ahead of the horse. Get the coach loaded as you will travel, then weigh it. 4 corner weigh is best but at minimum weigh each axle. Then go to tire manufacturer's inflation tables for your specific tire and wheel position. Wen psi you determine from the charts is the psi you are looking for. Just for safety I add 5 psi above chart psi.
Hope this helps you get 'er done
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KIX
'02 Ultimate Advantage 40J Spartan MM - Cummins ISC
2013 Jeep Rubicon JK Unlimited
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12-03-2012, 09:12 PM
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#3
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Moderator Emeritus
Join Date: Jan 2007
Location: Litchfield Park, Arizona
Posts: 10,530
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I suspect what the tech told you was correct for carrying maximum weight but you're nowhere near that in all probability. It would be fine (and safe) to inflate them to those pressures but if you're programming a TPMS I would think you'd want to do it only once so "get thee to a Cat scale" and get the right numbers.
Rick
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Rick, Nancy, Peanut & Lola our Westie Dogs & Bailey the Sheltie.
2007 Itasca Ellipse 40FD
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12-03-2012, 09:20 PM
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#4
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Senior Member
Country Coach Owners Club Solo Rvers Club iRV2 No Limits Club
Join Date: May 2011
Location: Vancouver, WA
Posts: 37,725
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Quote:
Originally Posted by RickO
I suspect what the tech told you was correct for carrying maximum weight but you're nowhere near that in all probability. It would be fine (and safe) to inflate them to those pressures but if you're programming a TPMS I would think you'd want to do it only once so "get thee to a Cat scale" and get the right numbers.
Rick
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Most CAT scales I've seen won't let you get four "corner" weights and that's what you really need. Most of the tire manufacturers publish an RV tire guide. A copy of that from your tire manufacturer would set you on the right track. I have them for Michelin, GoodYear and TOYO and there may be others.
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2009 45' Magna 630 w/Cummins ISX 650 HP/1950 Lbs Ft, HWH Active Air
Charter Good Sam Lifetime Member, FMCA,
RV'ing since 1957, NRA Benefactor Life, towing '21 Jeep JLU Rubicon Ecodiesel
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12-03-2012, 10:43 PM
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#5
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Community Moderator
Join Date: Sep 2011
Location: Between the Oceans
Posts: 8,034
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Thanks everyone for your fast response. It seems I do need to weigh 4 corners at the earliest possibility. I am indeed nowhere near max load, maybe before I can get actual weight numbers I should set TPMS to front 115 and rear 110? currently it was filled with 105 psi all around by the tire shop where I bought the new tires.
__________________
Steven & Polly
2000 Country Coach Intrigue 40' ISC 350
2018 Ford Explorer 4WD
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12-04-2012, 10:39 AM
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#6
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Senior Member
Commercial Member
Join Date: Mar 2010
Location: Akron, Ohio
Posts: 2,785
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You should have a tire placard or certification label in your coach. This is the manufacturer's recommendation that you should use untill you confirm through scale weight, that you can run less.
HERE is a web page with general info and a worksheet on how to calculate your "corner" weights. I found a local builder's supply co that had a truck scale and would do the multi weight needed for RVs for about $10.
NOTE all the above applies to Motorhomes. If a reader has a trailer with ST type tires they should always run the inflation molded on the tire sidewall. They should still confirm they are not part of the 57% of owners that have one or more tire or axle overloaded.
__________________
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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12-04-2012, 02:11 PM
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#7
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Senior Member
Newmar Owners Club
Join Date: Jul 2006
Location: Wellington, Florida
Posts: 13,599
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Hi sdlcrazier,
FYI, the weight on my rear axle is right at 20K (GAWR). You're drive axle should be the same GAWR (20K). Michelin says 95 PSI in all 4 tires. The front is a bit more tricky. There are many different front axle weight ratings for front axles. My front axle is rated at 12.5K. I am running 11.8K. Michelin says 105 PSI on the front tires.
This is FYI only. The tire manufacturer chart for PSI is your bible on this topic.
__________________
Gary
2005 Newmar KSDP 3910 + GMC ENVOY XUV 37K lbs Moving Down The Road
The Avatar Is Many Times Around The USA
Nobody Knows Your Coach Like Somebody Who Owns One Just Like Yours
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12-04-2012, 02:36 PM
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#8
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Community Moderator
Join Date: Sep 2011
Location: Between the Oceans
Posts: 8,034
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the placard on the wall near driver seat shows max 120psi front and 110 on rear cold. the max load on all tires is 120psi. so, before weighing it, i am reluctant to put on max load, so i am going to pump up and set to 115 front and 110 rear. now i know i am safe and in line with everyone . upon weighing i might adjust these accordingly... thanks everyone.
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Steven & Polly
2000 Country Coach Intrigue 40' ISC 350
2018 Ford Explorer 4WD
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12-04-2012, 03:25 PM
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#9
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Senior Member
Damon Owners Club Workhorse Chassis Owner
Join Date: Mar 2009
Posts: 24,024
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RV Safety & Education Foundation has a link to weighing
They call, do a short phone interview.. Come out, find a spot meet you weigh your rig (all 4 corners) and provide you with the proper pressure for YOUR tires (that's what the interview is about, Make and model and size of tire).
If you can not find a lower cost scale that can do 4 corner weights, Give 'em a call. or E-mail.
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Home is where I park it!
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12-04-2012, 03:50 PM
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#10
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Registered User
Join Date: Aug 2012
Location: The Land Of Oz RVM17
Posts: 1,592
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If you get the axle weight and divide by two you will have a close enough weight for tires. Say front axle scales 18,000 pounds, I would just figure 9,000 for each side and base air pressure off this. We always run the same pressure on the steer of semi trucks as most alignment shops say a low tire on one side can cause it to pull. And they may very some side to side but not much. A motor home is a little different animal. Don't overload it, and try to balance cargo in the basement and coach. If it handles good then don't worry. Just keep tires to a correct pressure.
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12-05-2012, 12:44 PM
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#11
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Senior Member
Commercial Member
Join Date: Mar 2010
Location: Akron, Ohio
Posts: 2,785
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Quote:
Originally Posted by KSCRUDE
If you get the axle weight and divide by two you will have a close enough weight for tires. Say front axle scales 18,000 pounds, I would just figure 9,000 for each side and base air pressure off this. We always run the same pressure on the steer of semi trucks as most alignment shops say a low tire on one side can cause it to pull. And they may very some side to side but not much. A motor home is a little different animal. Don't overload it, and try to balance cargo in the basement and coach. If it handles good then don't worry. Just keep tires to a correct pressure.
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It is not unusual for axles to be out of balance by 1000# according to RVSEF.
Check THIS link here on iRV2
TYPE Class-A
RF - 4650#
LF - 4950#
RR - 9050#
LR - 7800#
As you can see these are a long way from 50/50.
As a minimum I suggest you calculate that you have a 55/45 side to side balance on the motorhome until you get data that confirms otherwise. You would select the inflation for all tires on the axle based on the heaviest tire load.
__________________
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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