What PSI to run?

[darrellr]

Dual means 4 wheels per axle, not 2 wheels per axle. Yes, assuming your trailer is loaded such that weight is distributed evenly on all 4 wheels. Once you know how much your trailer weighs, you can lower your pressure to that weight rating if you want to.

 

[D W]

This question gets asked and answered every month on this forum. Just look at the sidewall of the tire.

 

[5picker]

This question gets asked and answered every month on this forum. Just look at the sidewall of the tire.

And this recommendation is one of the reasons it gets asked every month.

The sidewall pressure is the MAX recommended pressure for the load the tire is rated to carry.
If you are not carrying the full load the tire is rated for, the manufacturers recommendations for inflation comes from their chart.

 

[fobagbob]

And this recommendation is one of the reasons it gets asked every month.

The sidewall pressure is the MAX recommended pressure for the load the tire is rated to carry.
If you are not carrying the full load the tire is rated for, the manufacturers recommendations for inflation comes from their chart.

Agree 100%. For our two motorhomes, that lower than sidewall pressure resulted in a better ride and more responsive steering.

 

[Chuck_S]

Dual is like in "dualie" or a pair of wheels on each end of the axle like a semi or four tires/axle.

Yep, at 80psi each tire can support 3640 pounds or 14,560 pounds for all four (kinda like what I posted a week ago ). And no more than 90% of your trailer's weight is on the tires as the tongue needs at least 10%. You probably have less than 13,000 pounds on the wheels. Easy to run it thru the Cat Scales.

-- Chuck

 

[tomupnorth]

New to trailering and our Surveyor's sticker is a bit confusing to me. It's a single axle TT with a single wheel/tire each side. The sticker indicates GAWR is 4400lb but the GVWR is shown as 4849lb--shouldn't these be the same?

Also, with a dry weight of 4130 assuming just for the sake of discussion 470# of added weight or ~4,600# total, now I've exceeded the GAWR!?

Finally, again assuming 4600# trailer weight loaded, then each wheel would be asked to bear 2300# in which case...

...it appears I could set my PSI as low as 55?

Whaddyins think?

 

[pgandw]

I would give yourself a little bit of cushion above the axle rating (10%) for dynamic load transfers, which puts you at 2440 lbs/tire, which also covers your GVWR. Maybe 61 PSI? To be honest, your tires are none too big for the loaded camper, with a minimal reserve at full inflation. In your shoes, I would just set the tires at 65PSI and keep them there. Over-inflation causes little harm other than more bounce to the trailer going down the road. Under-inflation can cause several different short and long term problems - mostly from heat or hitting pot holes and curbs.

Fred W
2019 Flagstaff T21TBHW A-frame
2022 Hyundai Palisade

 

[tomupnorth]

I would give yourself a little bit of cushion above the axle rating (10%) for dynamic load transfers, which puts you at 2440 lbs/tire, which also covers your GVWR. Maybe 61 PSI? To be honest, your tires are none too big for the loaded camper, with a minimal reserve at full inflation. In your shoes, I would just set the tires at 65PSI and keep them there. Over-inflation causes little harm other than more bounce to the trailer going down the road. Under-inflation can cause several different short and long term problems - mostly from heat or hitting pot holes and curbs.

Fred W
2019 Flagstaff T21TBHW A-frame
2022 Hyundai Palisade

Makes sense thanks Fred. I will fine-tune once I've gotten the rig loaded and onto the scales.

 

[D W]

New to trailering and our Surveyor's sticker is a bit confusing to me. It's a single axle TT with a single wheel/tire each side. The sticker indicates GAWR is 4400lb but the GVWR is shown as 4849lb--shouldn't these be the same?

View attachment 740875

Also, with a dry weight of 4130 assuming just for the sake of discussion 470# of added weight or ~4,600# total, now I've exceeded the GAWR!?

Finally, again assuming 4600# trailer weight loaded, then each wheel would be asked to bear 2300# in which case...

View attachment 740876

...it appears I could set my PSI as low as 55?

Whaddyins think?

Don't forget, 10-12% of your GW goes on your TV tongue. Pneumatic tires have been around for over 100 years. This isn't rocket science. Don't overthink the situation. I air mine up to the 80 psi cold instructions on the sidewall and head out. The tires ride well and wear evenly. I've only had one blow out in the past 10 years, and that was caused by a road hazard.

 

[tomupnorth]

Don't forget, 10-12% of your GW goes on your TV tongue. Pneumatic tires have been around for over 100 years. This isn't rocket science. Don't overthink the situation. I air mine up to the 80 psi cold instructions on the sidewall and head out. The tires ride well and wear evenly. I've only had one blow out in the past 10 years, and that was caused by a road hazard.

Haha DW you're reminding me of one of my High School teachers when a student would say "I forgot":
"In Order to FORGET, you first must KNOW"!

I never thought about the tongue weight.

Of course. Hey buddy I overthink EVERYTHING and this new TT will be no exception. We had been looking at dual-axle trailers and after falling for this one it troubles me just a bit that a blowout could be disasterous.

Our Class C motorhome years ago had duallies.

 

[rxgac]

Before considering inflating to 110, you need to check if the rims are rated to 110. Should be listed somewhere on the rim

 

[slhicks]

Hello all,

I recent purchased a 2019 FR XLR Boost 36DSX13. Everything looks good except for the Castle Rock tires which are factory original (235/80/16 @80 PSI E rated). I upgrade the tires to the Sailun s637's G rated (235/85/16) as well as metal fill stems and a TPMS system. On the tire placard it shows 80 PSI but the new tires are 110. The trailer dealer who suggested upgrading the tires/fill stems/tpms in the first place said running at 110 is not going to be a problem, but I am worried about the factory rims pressure cracking. There were no pressure markings anywhere on the rims.

Should I be running these at 110 PSI for my max load of 14k lbs? Ive done some googling and it ranges anywhere from people saying only use 80 PSI to 110 PSI to prevent over heating due to an underinflated tire. I have a 9 hour trip to bring the trailer home and I really want to make it in one piece.

Just went thur that myself. Internet says go with the recommended pressure on the tire. Better yet brother in law and his dad, retired diesel mechanic and retired trucker, also said go with tire pressure on tire side wall.

 

[juice5]

Hello all,

I recent purchased a 2019 FR XLR Boost 36DSX13. Everything looks good except for the Castle Rock tires which are factory original (235/80/16 @80 PSI E rated). I upgrade the tires to the Sailun s637's G rated (235/85/16) as well as metal fill stems and a TPMS system. On the tire placard it shows 80 PSI but the new tires are 110. The trailer dealer who suggested upgrading the tires/fill stems/tpms in the first place said running at 110 is not going to be a problem, but I am worried about the factory rims pressure cracking. There were no pressure markings anywhere on the rims.

Should I be running these at 110 PSI for my max load of 14k lbs? Ive done some googling and it ranges anywhere from people saying only use 80 PSI to 110 PSI to prevent over heating due to an underinflated tire. I have a 9 hour trip to bring the trailer home and I really want to make it in one piece.

Before you Do anything ELSE ! Get a Price on Goodyear endurance tires and do it.......THOSE CHINA BOMBS PROVIDED BY MANUFACTURER/DEALER ( castle rock ) are only intended for the sales lot !.....NOT FOR CAMPING TRAVEL PERIOD ! CAstle Rock tires Only performance is " FAILURE AT THE WRONG TIME AND DOIN IT TWICE ! .....or more ! best wishes juice !

 

[NXR]

Just encountered something new with the forum software. Something like "There are more posts. View them?"

Not seeing that I duped other responses so now I can't figure out how to delete a post.

Ray

 

[jadatis]

Hello all,

I recent purchased a 2019 FR XLR Boost 36DSX13. Everything looks good except for the Castle Rock tires which are factory original (235/80/16 @80 PSI E rated). I upgrade the tires to the Sailun s637's G rated (235/85/16) as well as metal fill stems and a TPMS system. On the tire placard it shows 80 PSI but the new tires are 110. The trailer dealer who suggested upgrading the tires/fill stems/tpms in the first place said running at 110 is not going to be a problem, but I am worried about the factory rims pressure cracking. There were no pressure markings anywhere on the rims.

Should I be running these at 110 PSI for my max load of 14k lbs? Ive done some googling and it ranges anywhere from people saying only use 80 PSI to 110 PSI to prevent over heating due to an underinflated tire. I have a 9 hour trip to bring the trailer home and I really want to make it in one piece.

Its best to treath your new ST tires as if they where LT .

In the Goodyear list, both are given in your new size 235/85R 16
The Endurance ST in same loadindex 132( single) maxload 4409 lbs AT 110 psi, wich is same as your new tire but yours give L speedrated for max 75 mph, and the Goodyear N for max 87 mph.

But also the Unisteel G614 RST loadindex 126 / 3750 lbs AT 110 psi. Q speedrated or more for wich maxload is calculated for 99 mph.

It not bad to give the ST the same deflection as the LT needed for 99mph.
I determined once that using 90% of calculated loadcapaciry for 99 mph , gives still acceptable gripp, and wont tremble your screws loose.

Will give in next post my made list for your new tire, per tandem and totalweight given, so you dont need to do pre- or after-calculations yourselfes.

 

[jadatis]

Here the promesed list.

Is for as if LT 3750 lbs AT 110 psi.
Gives in front of cold psi , total weight on tandem, so 4 tires singleload ( 2 tires on 1 axle) , being 90% of calculated loadcapacity, calculated with an even tighter formula then the official in Europe used by ETRTO for all kind of tires, and since 2006 also used in US for P-tires.
So maximum reserve build in for speed and load.

Behind cold psi for totalweight of trailer, asuming the minimum 10% of total on towbar ( or do you have a 5thwh, then I have to correct, upto 20% on plate)

Then your GVWR 14560 LBS gives 106 to 107 psi, and so the 110 psi mentioned by tirefitter, is not that bad.
A higher loadrange tire ( as your new G-loads are then old E-loads in slightly smaller size)of same size, needs a bit higher pressure for same load( or lower loadcapacity for same pressure).


So as long as you did not weigh fully loaded as going on trip, per axle, or better even per axle-end , wich is best, you have to go from GVWR, and hope not overloaded, and my list gives maximum reserve, at wich gripp and "comfort"( that screws not tremble loose, upto doors open after the ride) is still acceptable

Made list in steps of 2 psi, but you could round up to 5 psi. Interpolation is allowed, and because maximum reserve, you could round down too if only 100 lbs less.

Tandemweight/ cold psi/ totalweight,towbar10%
5300lbs/ 40,0 psi/5889lbs
5541lbs/ 42,0 psi/6156lbs
5781lbs/ 44,0 psi/6423lbs
6021lbs/ 46,0 psi/6690lbs
6260lbs/ 48,0 psi/6956lbs
6499lbs/ 50,0 psi/7221lbs
6737lbs/ 52,0 psi/7486lbs
6975lbs/ 54,0 psi/7750lbs
7213lbs/ 56,0 psi/8014lbs
7450lbs/ 58,0 psi/8278lbs
7686lbs/ 60,0 psi/8541lbs
7923lbs/ 62,0 psi/8803lbs
8159lbs/ 64,0 psi/9065lbs
8394lbs/ 66,0 psi/9327lbs
8629lbs/ 68,0 psi/9588lbs
8864lbs/ 70,0 psi/9849lbs
9098lbs/ 72,0 psi/10109lbs
9332lbs/ 74,0 psi/10369lbs
9566lbs/ 76,0 psi/10629lbs
9800lbs/ 78,0 psi/10889lbs
10033lbs/ 80,0 psi/11148lbs
10266lbs/ 82,0 psi/11407lbs
10498lbs/ 84,0 psi/11665lbs
10731lbs/ 86,0 psi/11923lbs
10963lbs/ 88,0 psi/12181lbs
11195lbs/ 90,0 psi/12439lbs
11426lbs/ 92,0 psi/12696lbs
11658lbs/ 94,0 psi/12953lbs
11889lbs/ 96,0 psi/13210lbs
12119lbs/ 98,0 psi/13466lbs
12350lbs/ 100,0 psi/13722lbs
12580lbs/ 102,0 psi/13978lbs
12810lbs/ 104,0 psi/14234lbs
13040lbs/ 106,0 psi/14489lbs
13270lbs/ 108,0 psi/14745lbs
13500lbs/ 110,0 psi/15000lbs/
referencepressure

13729lbs/ 112,0 psi/15254lbs
13958lbs/ 114,0 psi/15509lbs
14187lbs/ 116,0 psi/15763lbs
14415lbs/ 118,0 psi/16017lbs
14644lbs/ 120,0 psi/16271lbs

 

[jadatis]

About your rimms.
In Europe max cold pressure of rimms is not given, only maxload or loadindex.

So maxpress of rimms is here not seen as important. But OK this is the idea of us cheating europeans.
And what counts to laws of nature are the real weights, wich havent changed .

 

[Papadave-FRF]

You were right to be concerned about the rims. Castlerock is distributed by “lionshead” . That company imports lots of different tire brands and also rims. If you search for lionshead rim failure you will see reports of cracked rims. Criminal neglect on the part of trailer manufacturers to use these suppliers. After my CB’s exploded. I did a bit of research and found lawsuits between the company and the suppliers in China regarding their ignoring things like gluing the tread layers together. Unfortunately the NTSB also recall a series of Saluns for quality issues.

 

[jadatis]

But then the rimms must have been inadequaye for the 80 psi or lower maxload of tires . So then new rimms with 4410 maxload minimally topicstarter has to search for.

 

[Tireman9]

View attachment 740854

So this is the PSI chart for the 235/85.16's. Im a little confused as to what "Dual" and "Single" are referring to. I'm assuming my trailer is single? So at 80 PSI Id have 3640 lbs per tire? WHich would be 14,560lbs total which is the weight of the entire trailer loaded anyway.

"Duals" are when 2 tires are mounted side by side on the same axle end., so 4 tires on the same axle. This is what you see on the rear of Semi-Trailers. Here is a link to the post on "Duals" with pictures from my RVTire Blog.

How to replace a tire in "Dual" application

First off if you have a towable RV and your tow vehicle only has four tires you can go get a cup of coffee as this post doesn't apply to you...

www.rvtiresafety.net