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08-11-2016, 01:40 PM
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#21
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Commercial Member
Join Date: Jul 2013
Location: Akron, Ohio
Posts: 1,889
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Quote:
Originally Posted by abi2001
Greenimp: the placard on our rig reads maximum, not minimum. We do know the difference. Thanks.
Airdale: this is what I read and understand too. I even found some great comparative charts online. I expressed that info and concern to my hubby but he said (claims/thinks) the hitch weight makes up for the extra support and wasn't worried about it, choosing to keep it at 65 because the run between 70-75 when riding. I agree with you completely. Thank you so much!
The tires currently appear to have bulges in the sidewalls, so it looks like they have internal damage from ride underinflated. I'm currently trying to convince hubby to upgrade the wheels and tires to 16-inch.
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Your 70-75 psi is a HOT pressure and is not part of the discussion. The ONLY inflation to consider is the "cold" inflation. i.e. when tires have not been driven on or exposed to direct sunlight for the past two hours.
Stop guessing on the tire loading. Get on a truck scale and learn the INDIVIDUAL actual load on each axle. You will find the total of the axles is not equally distributed between axles. Once you know the actual load on each axle you should assume a 53/47% side to side split as almost no RV has its axle load split 50/50 side to side on all axles. The problem is you don't know which end is the heavy end so using the heavier end load number consult the load tables. This will tell you the MINIMUM cold inflation you need not based on a guess but based on facts and actual measurement.
All tires on an axle should get the same cold inflation.
__________________
.Write a blog on RV tire application RV Tire Safety. 48 years experience as tire design & forensic engineer. My RV Freelander 23QB on Chevy 4500 chassis. Giving seminars on RV Tire applications (not selling)@ FMCA Conventions. Mar 20-22 Tucson AZ
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08-11-2016, 04:51 PM
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#22
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Senior Member
Join Date: Jul 2013
Posts: 1,839
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Lets look at this from the manufacturers view-point. The specs for the 31SAX fiver says it has a GVWR of 12060#. So the published hitch (1660#) weight is subtracted from that leaving 11400# on the axles. Divided by 2 = 5200# GAWR axles. What does the certification label have for GAWR (S)?
Wildcat Fifth Wheels / Travel Trailers by Forest River RV
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A Trailer Tire Poster
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08-11-2016, 05:17 PM
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#23
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Carknocker Family
Join Date: Mar 2013
Location: Arkansas
Posts: 690
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Quote:
Originally Posted by Airdale
Lets look at this from the manufacturers view-point. The specs for the 31SAX fiver says it has a GVWR of 12060#. So the published hitch (1660#) weight is subtracted from that leaving 11400# on the axles. Divided by 2 = 5200# GAWR axles. What does the certification label have for GAWR (S)?
Wildcat Fifth Wheels / Travel Trailers by Forest River RV
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11400# divided by 2 is 5700.
5700# divided by 2 is 2850. That is the reason for the 10 ply tires. Air tire to 80 psi. Get Forest River to issue you a new placards.
If you have been running tire to placard psi, you may have permeantly damaged your tires and will be needing replacement.
IMO
__________________
Nights camped 2015...20
Nights camped 2016...20
Nights camped 2017...24
2017 Ram 2500
2014 Salem 32BHDS
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08-11-2016, 09:44 PM
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#24
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Junior Member
Join Date: Apr 2016
Posts: 16
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Update from OP: my husband finally took my advice. We've since upgraded our tires to 16" 14-ply, with rims to match and support. They're getting installed Saturday. Can't tell how tickled pink I am about the upgrade!
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08-12-2016, 07:05 AM
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#25
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Senior Member
Join Date: May 2015
Posts: 1,397
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The 80psi is the maximum cold pressure for an E-rated tire. However, in your case FR has determined 65psi is adequate based on your trailer weight. You can run the tires anywhere between 65-80psi. At 80psi, the ride will be a bit harsher.
__________________
--2005 F350 Superduty Crewcab, 6.0, 4wd, short bed, 3.73 gears;
--2016 Montana 3711FL, 40'
--2014 Wildcat 327CK, 38' SOLD
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08-12-2016, 09:18 AM
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#26
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Member
Join Date: Feb 2016
Location: Idaho
Posts: 33
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Sorry to jump in towards the end of this thread. I can start a new post if the moderators think so.
My tire pressure question is a little different. I've always believed that side-wall stress and tire wear were the two things you should be concerned with. The former is the culprit for blowouts. I've taken my 2016 Rockwood 5th wheel to a CAT scale near my home and have numbers for all of the axle, total, hitch, etc weights necessary to understand my rig. I live in Idaho and we can get temperature swings of 40 - 50 degrees between early morning hours to highs in the afternoon. It wouldn't be unusual to have cold temperature pressures to change drastically throughout the day. Not to mention the pressure differences due to altitude changes. I can leave my house at 4740' MSL altitude and 45 degrees F) and end up at a campground later in the day at 7100' MSL altitude and 90 degrees F. If conditions like that make a 3 - 5 psi difference in your tires (cold temp measurements), do I need to be worried about blowouts or just tire wear changes. I'm not sure how much pressure change from the max or recommended will adversely affect your tires?
Am I on ok here or do I need to watch the tire pressure more carefully?
__________________
2013 GMC Sierra 2500 HD, Duramax
2016 Forest River Rockwood 8299BS
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08-12-2016, 09:21 AM
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#27
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Left Coast
Join Date: Dec 2014
Location: vancouver,washington
Posts: 15,649
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Which tire and load rating?
Sent from my XT1585 using Tapatalk
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08-12-2016, 09:41 AM
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#28
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Member
Join Date: Feb 2016
Location: Idaho
Posts: 33
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Quote:
Originally Posted by bob caldwell
Which tire and load rating?
Sent from my XT1585 using Tapatalk
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My rig is in storage at the moment so I can't remember what tires I have but the max tire pressure is 65 psi cold and has a load D rating. Btw, after these tires (new with purchase of camper) wear out, I'm going with a load E tire.
I'm going to my camper later today and can get more detailed information if you need that.... Thanks!
__________________
2013 GMC Sierra 2500 HD, Duramax
2016 Forest River Rockwood 8299BS
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08-12-2016, 09:51 AM
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#29
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Crookedread
Join Date: Oct 2010
Location: Hillsboro
Posts: 118
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I couldn't agree with Tireman9 more! I have a toy hauler and before I head out I weigh all of the axles and then weigh one side of the axles to make sure I'm not overloaded side to side. I have even added a link to the preset on the equalizer hitch to see what it did to the overall balance of weight right at the scaled. Pulling the 8000# trailer was a dream with my Toyota Tundra because I had everything balanced. I recently upgraded the TV but am setting up the new rig the same way.
Crookedread
2016 Duramax
2011 Stealth 2312
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08-12-2016, 09:55 AM
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#30
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Left Coast
Join Date: Dec 2014
Location: vancouver,washington
Posts: 15,649
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My opinion is you should be fine.....I'M M in the middle of a tire tesr, testing both D and E rated tires at the same time, and different brands....have approx 4000 miles on this, running 65 lbs cold....
Sent from my XT1585 using Tapatalk
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08-12-2016, 10:10 AM
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#31
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Member
Join Date: Feb 2016
Location: Idaho
Posts: 33
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Quote:
Originally Posted by bob caldwell
My opinion is you should be fine.....I'M M in the middle of a tire tesr, testing both D and E rated tires at the same time, and different brands....have approx 4000 miles on this, running 65 lbs cold....
Sent from my XT1585 using Tapatalk
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Interesting...I can't wait to see your results. Do you have any preliminary results with 4K miles on them?
__________________
2013 GMC Sierra 2500 HD, Duramax
2016 Forest River Rockwood 8299BS
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08-12-2016, 11:56 AM
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#32
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Left Coast
Join Date: Dec 2014
Location: vancouver,washington
Posts: 15,649
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Good so far....from Nebraska to N. Carolina and back to here
Sent from my XT1585 using Tapatalk
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08-12-2016, 04:20 PM
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#33
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Commercial Member
Join Date: Jul 2013
Location: Akron, Ohio
Posts: 1,889
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Quote:
Originally Posted by jstaffon
Sorry to jump in towards the end of this thread. I can start a new post if the moderators think so.
My tire pressure question is a little different. I've always believed that side-wall stress and tire wear were the two things you should be concerned with. The former is the culprit for blowouts. I've taken my 2016 Rockwood 5th wheel to a CAT scale near my home and have numbers for all of the axle, total, hitch, etc weights necessary to understand my rig. I live in Idaho and we can get temperature swings of 40 - 50 degrees between early morning hours to highs in the afternoon. It wouldn't be unusual to have cold temperature pressures to change drastically throughout the day. Not to mention the pressure differences due to altitude changes. I can leave my house at 4740' MSL altitude and 45 degrees F) and end up at a campground later in the day at 7100' MSL altitude and 90 degrees F. If conditions like that make a 3 - 5 psi difference in your tires (cold temp measurements), do I need to be worried about blowouts or just tire wear changes. I'm not sure how much pressure change from the max or recommended will adversely affect your tires?
Am I on ok here or do I need to watch the tire pressure more carefully?
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Tire pressure changes by 2% for each change of 10F in Ambient. Altitude does affect inflation but not a lot.
Here are some posts that I think will answer your questions.
"Blowouts" do not occur due to normal pressure changes but they do occur form running low on inflation.
Get a TPMS. Learn how to set and use it and you can figure you just eliminated 40 to 60% of the reasons for a tire failure.
__________________
.Write a blog on RV tire application RV Tire Safety. 48 years experience as tire design & forensic engineer. My RV Freelander 23QB on Chevy 4500 chassis. Giving seminars on RV Tire applications (not selling)@ FMCA Conventions. Mar 20-22 Tucson AZ
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08-12-2016, 11:01 PM
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#34
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Member
Join Date: Feb 2016
Location: Idaho
Posts: 33
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Quote:
Originally Posted by Tireman9
Tire pressure changes by 2% for each change of 10F in Ambient. Altitude does affect inflation but not a lot.
Here are some posts that I think will answer your questions.
"Blowouts" do not occur due to normal pressure changes but they do occur form running low on inflation.
Get a TPMS. Learn how to set and use it and you can figure you just eliminated 40 to 60% of the reasons for a tire failure.
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Thanks to all on this topic.
Tireman9,
Those are good numbers to know. Thanks!
__________________
2013 GMC Sierra 2500 HD, Duramax
2016 Forest River Rockwood 8299BS
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08-16-2016, 01:45 PM
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#35
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Commercial Member
Join Date: Jul 2013
Location: Akron, Ohio
Posts: 1,889
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Quote:
Originally Posted by bob caldwell
My opinion is you should be fine.....I'M M in the middle of a tire tesr, testing both D and E rated tires at the same time, and different brands....have approx 4000 miles on this, running 65 lbs cold....
Sent from my XT1585 using Tapatalk
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Interesting. If you are running same inflation on LR-D and LR-E what are you expecting to see?
What % of actual measured load is each tire rated for at 65psi?
So if you see some difference how will you know if it is because of brand, Load Range or actual tire load by position?
Is tour TPMS giving any indication of difference?
__________________
.Write a blog on RV tire application RV Tire Safety. 48 years experience as tire design & forensic engineer. My RV Freelander 23QB on Chevy 4500 chassis. Giving seminars on RV Tire applications (not selling)@ FMCA Conventions. Mar 20-22 Tucson AZ
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08-17-2016, 09:03 AM
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#36
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Left Coast
Join Date: Dec 2014
Location: vancouver,washington
Posts: 15,649
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Don't have a TPMS yet, but mostly brand against brand..,..I'm under max weight, and on last trip to NYC rally, had 2 tire failers,, do to age....approx 5years......one tire went bad just leaving Nebraska, and tire place only had 2 tires E rated...no other C or D's. Then leaving Missouri, next one went....found a Walmart bout a mile away, same result...had 2 tires, D rated....no chose then..,was running 80 in originals, but beat the trailer to death, so went back to 65 on these....with Arizona trip coming up, and the TV show, TPMS is in the future...
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