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09-13-2016, 08:42 PM
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#1
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Member
Join Date: Oct 2012
Location: Houston, Tx
Posts: 95
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Tire Pressure Sanity Check
Just because there aren't enough threads about Tire Pressure...and I think I've read them all, however, the numbers I have come up just seem low.
2004 CC Intrigue 40' Tag. I just put on new 8 XZA2 Energy 315 80R 22.5.
The badge on the coach called for 120-110-120 (steer,drive,tag), but that was on the H Rated Toyo 12r's.
These new tires are "L" rated with MAX of 130.
The coach weights are the following:
Front - 14,500/2 = 7250
Drive - 22000/2 = 11,000
Tag - 12000/2 = 6000
Total = 48.5K
Using the chart for this tire on Michelins site, they say the following:
Front - 105
Drive - 85
Tag - 85
Seems low to me...thoughts, comments, suggestions?
Thanks,
Dan
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09-13-2016, 08:45 PM
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#2
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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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Well, first off the pressure on the sidewall of a truck size tire is not the maximum it should ever have. It is the minimum to support the maximum rating of the tire.
If you've read the charts right with the correct weights then I would take the chart pressure and add 5 psi to it since you don't have four "corner" weights.
__________________
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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09-13-2016, 09:18 PM
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#3
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Senior Member
Fleetwood Owners Club Ford Super Duty Owner
Join Date: Jun 2012
Location: SoCal
Posts: 15,749
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Quote:
Originally Posted by Mr_D
If you've read the charts right with the correct weights then I would take the chart pressure and add 5 psi to it since you don't have four "corner" weights.
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Agree.
__________________
Vince and Susan
2011 Tiffin Phaeton 40QTH (Cummins ISC/Freightliner)
Flat towing a modified 2005 Jeep (Rubicon Wrangler)
Previously a 2002 Fleetwood Pace Arrow 37A and a 1995 Safari Trek 2830.
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09-13-2016, 09:43 PM
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#4
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Senior Member
Monaco Owners Club
Join Date: Jun 2015
Posts: 377
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Seems about right, and X3 with Mr D.
.
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Loving the Beaver!
Jason, Sherri, Christian, & Wheeler (Golden Retriever)
2008 Beaver Contessa Huntington CAT C9 400hp FMCA F25478 S4
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09-14-2016, 05:00 AM
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#5
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Senior Member
Thor Owners Club Ford Super Duty Owner
Join Date: Jul 2011
Posts: 3,796
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Going from a load range H to L I would expect to see a drop in recommended pressures for the same weight. Since the new tires are not the same class as originally installed (load range change) on the coach the builder's placard is no longer applicable. Sticking with Michelin's recommended pressures with an addition 5 PSI to account for variations in day to day loading and temperature changes.
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09-14-2016, 12:16 PM
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#6
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Senior Member
Join Date: Dec 2013
Location: Lake Havasu City, AZ & Plover, WI
Posts: 6,403
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If you look at a load chart for the H rated tire for a given weight and compare it to the recommended pressure for the same weight on an L rated tire, the numbers will be the same. The L of course can carry more weight, but at a higher pressure. When I asked a Michelin rep about the different minimum pressure ratings he said they were correct and that I could run more as long as I did not exceed the amount listed on the side of the tire. He said that all of the different psi ratings were the minimum, however, the 120 psi on the side of my tire was the minimum cold pressure for the load, but was also the maximum cold psi for the tire.
EDIT: I need to correct part of my statement: I just put on some G rated trailer tires replacing E rated ones. It uses the same load range chart, however, continues past the maximum load for the "E" rating to the max for the "G". To carry 3000# for either tire the min psi is the same. This may no apply to the 22.5 RV tires.
__________________
2006 Monaco Executive 44 Denali
2013 43 QGP Allegro Bus ( SOLD )
2013 Avalanche
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09-14-2016, 05:16 PM
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#7
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Senior Member
Join Date: Nov 2011
Posts: 884
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Go by the chart...
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09-14-2016, 06:50 PM
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#8
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Moderator Emeritus
Join Date: Jan 2000
Location: West Palm Beach, FL. USA
Posts: 27,713
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Go by the Michelin chart fopr that model and size. The Toyo's were a smaller tire (12R is smaller than 315/80), so naturally the required pressure was higher.
As others have explained, the L vs H rating has little to do with pressure requirements - it's mostly a higher max load & psi. And you can only compare load range & psi for identical size tires anyway. With different sizes, all bets are off.
__________________
Gary Brinck
Former owner of 2004 American Tradition and several other RVs
Home is West Palm Beach, FL
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09-15-2016, 02:57 PM
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#9
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Senior Member
Join Date: Nov 2009
Location: Warren, Oregon
Posts: 2,560
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I got a new set of Michelin 295/80R22.5 XZA2. I had my coach weighted at the FMCA Rally in Albany,Or (4 corner wt) With a combined wt of 33,620lbs FR 6,405lbs-FL 6,065lbs RR 10,195lbs-LR 10,955lbs I need to run 105 PSI in the front and 100 PSI in the rear. They give you a print out of your coach wt's and the air pressure to run. This is the only way to get a true wt reading and know what PSI to run, money well spent.
2 stroker
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2006 Country Coach Inspire 360 40ft Genoa Designer Series, Samsung 197 RR
Cat C9--STEEL & COPPER Bolt Together Radiator w/ updated rubber mounting
SilverLeaf 330 Magnum 2812 PSW 2011 Ford Edge Sport-Air Force One
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09-15-2016, 03:07 PM
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#10
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Senior Member
Holiday Rambler Owners Club
Join Date: Aug 2010
Posts: 9,751
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Pressure numbers look about right for 315/80's.
BTW...... Thats one heavy 40' coach!
__________________
Ben & Sharon
2008 43' Holiday Rambler Scepter PDQ
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