Tire inflation

[Shoe2728]

Got E rated tires installed, 80psi max, Tire guy said it would be better to run around 65-70 psi as tires heat up. Always thought I should run max cold rating 80psi. FW weight is around 9000 lbs hooked up to truck.

[MM49]

I have always said "there is no such thing as a stupid questions only a stupid person asking it”
Run all or your trailer tires at max sidewall pressure. The forces implied on a tire are not always even. You touch one curb or hole in the road and you could be at a much higher load. The multiple axle system is a balance one. Just do the calculations when TT backs up a 2' hill.
MM49

[Cummins12V98]

phillyg wrote:
Run them at max pressure indicated on the tires.

Are you saying you run 80psi on your 350 on all 4 tires all the time? If so how many miles did you get on your last set of tires?

[phillyg]

Run them at max pressure indicated on the tires.

[avvidclif1]

There is enough tire expertise on this group that they should be able to design the PERFECT trailer tire. If only the mfgs and engineers would listen to the pros.

[Me_Again]

rhagfo wrote:
Me Again, looking at your chart, if I took the time could likely find in my Owners Manual.
You like me have the optional 265/75-16E tires, the rear axle load rating is based on the stock 245/75-16E at 3,042# ea. 6,084# rating, With the 265/75-165E's ea. tire is rated at 3,415# so you don't need 80 psi to carry the axle load.

We have done our work, those that choose to run 80 psi in their LT E tires all the time will be rewarded with a very nice bald patch down the center of their tires. :S

What I did not note it the original post was that my truck is a bit of a handful to handle with 70-75 in the rear and no load. It also will knock your teeth out with 70-75 and no load, even with the Rancho 9000's set to 1.

I run the rears at 44 empty to account for small loads during day to day use. When I haul gravel and other heavy items I air up. I have a latch on air chuck and use that NOT connected to the air hose to air down and with the compressor to air up, as it beats hold a key to the valve stem or holding an air chuck by hand to air up.

Chris

[wilber1]

Th truck in my signature calls for 45 psi empty. There is no way I would go lower than.

[jadatis]

reaction to former post.
'
What you mean is that you would get centre wear of tire with 80 psi.
That wont happen. because there is a large range in wich the tires stays over the whole treath width to the ground.
Probably even if you really have only 70% of the weigth the pressure is calculated for on tire .

Then its best to keep the highest possible pressure with no bumping, to have as much possible reserve for things like, pressure loss in time, misreadings of pressure and weight, misyudging of weight, unequall load R/L etc.

[rhagfo]

Me Again, looking at your chart, if I took the time could likely find in my Owners Manual.
You like me have the optional 265/75-16E tires, the rear axle load rating is based on the stock 245/75-16E at 3,042# ea. 6,084# rating, With the 265/75-165E's ea. tire is rated at 3,415# so you don't need 80 psi to carry the axle load.

We have done our work, those that choose to run 80 psi in their LT E tires all the time will be rewarded with a very nice bald patch down the center of their tires. :S

[Me_Again]

As Barry notes above, this is from my 2001 Dodge 2500 4x4's manual.
Light load 45/40 Heavy load 55/70

I run 57/44 light and 57/70-75 heavy, because sometimes the pin weight has me pushing 6K a little on the rear. Tires are the optonal LT265/75R16E rated to 3415 each.

[wandering1]

Run 80psi. Under or over inflated tires heat up. Excess heat will damage tires. Get the facts contact the tire manufacturer.

[CapriRacer]

As usual, lots of opinions.

1) On every vehicle sold in the US, there is a vehicle tire placard which lists the original tire size and the specified pressure for that size. On motorized vehicles, the placard is usually found on the driver's doorframe, but it can also be found on other doors , other doorframes, the glovebox, fuel filler door or on the trunk lid. For trailers, it can be found on the left front corner, on the tongue, on a door, in a cabinet.

Find the vehicle tire placard and make a note of the tires size (including the letters) and the specified pressure.

2) Car manufacturers have generally done a decent job of sizing their tires relative to load carrying capacity. SUV and Light Truck manufacturers, not so much - although since 2008, they are on par with the car manufacturers. Trailer manufacturers are the worst of the bunch and many trailers have come with inadequate tires (from a load rating perspective).

3) If you are NOT using the tire size (including the letters) as listed on the vehicle tire placard, then you'll need to recalculate. The calculation isn't difficult, but does require the use of the tire load tables.

4) The owners manual should give you guidance about what inflation pressure to use, including what to use if the vehicle is not fully loaded (like an empty pickup truck). If the owners manual doesn't say anything about less than fully loaded, then the vehicle manufacturer probably intends for you to use the placard presure even when empty. (They do test the vehicle that way!)

5) Tire load tables are primarily for vehicle manufacturers to use. If the vehicle manufacturer has done a good job, the vehicle tire placard and owners manuals ought to be enough information.

6) Tire wear more affected by other things than inflation pressure. For example, steer tires tend to wear on the shoulders and drive tires tend to wear in the center. Inflation pressure has to be changed a lot to get the same affect. In other words, inflation pressure shouldn't be the first thing that comes to mind when you see uneven tire wear.

7) As a general rule, cars do NOT use the maximum inflation pressure of a tire. As a general rule, SUV's and light trucks do NOT use the maximum inflation pressure. As a general rule, trailers DO use the maximum inflation pressure.

[JIMNLIN]

Shoe2728 wrote:
I had St 235 80R 16E went to BF Goodrich Commercial T/A All-Season 235 85R 16E GVW of FW is 12000. I have looked for a pressure weight table but mostly all I fine is max inflation rate is 80 psi. I have a 2011 crossroads cruiser 305skp

Your OEM tires had around 3500 lb load capacity at 80 psi.
The LT235/85-16 E tires your using are rated at 3042 lbs capacity at 80 psi.
Your going to have to use max sidewall pressure to get the full 3042 lb capacity which is recommended for tires on a trailer anyway.

Our RV trailers with close spaced wheels in the center on the trailer have tremendous side stress placed on them as they slide sideways around a corner.....unlike a truck with tires at the corners with the front steering into the corners and the rear set following.
And of course most folks know know about low pressures = more heat generated at highway speeds.

So don't be fooled by truck tire pressure needs.
Apples vs oranges for your trailer.


Goodyear Tire and Rubber says .... weighing RVs
Special Considerations

"Unless trying to resolve poor ride quality problems with an RV trailer, it is recommended that trailer tires be inflated to the pressure indicated on the sidewall of the tire. Trailer tires experience significant lateral (side-to-side) loads due to vehicle sway from uneven roads or passing vehicles. Using the inflation pressure engraved on the sidewall will provide optimum load carrying capacity and minimize heat build-up."

and if you have over tired the trailer then this web has some excellent recommendations;

rvsafety.com

Tire Load and Inflation Ratings

Note: Towable – Travel Trailer/ 5th Wheel owners Due to the severe use conditions experienced by tires when axles are very close together – tire industry experts recommend maximum (sidewall) inflation pressure for towable tires unless this causes a sever over-inflation situation (20psi+), often referred to as the ‘basketball effect’. If this is your situation allow a 10 – 15psi safety margin above the minimum required inflation pressure.

[jadatis]

@ 06Fargo

If you are reacting to my post before this, then read next topic of mine.
http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/27477930.cfm

The tire makers determine a maximum load for a sertain pressure ( AT-pressure) so the tire has a sertain deflection, at wich it wont get to warm on sertain area's so the rubber stays flexible, and not harden out and damage at next bendings of it.

European tyre makers even allow 1.4 times the AT pressure cold.
I would not asume that for American tires , because I suspect American tire makers to set a for instance D-load designed tire in the market as E-load , using the reserve to laws of nature. This to fullfill the American Dream of bigger is better.
Once read that tires are tested with 2 to 3 times the At-pressure .
So this makes me conclude that you are allowed to fill higher.

Example : A tire maker designs a tire for D-load use with 65 psi AT-pressure . The absulute pressure the tire can stand even when driving then is between 130 and 185 psi before it blows.
If then the tire maker places it in the market ( with other print on sidewall) for E-load so At pressure of 80 psi, still the pressure wont go over 185 psi ( 3 x 65) when filled cold at freesing temp of water of 32 degr F , and the temperature inside the tire rises to even boiling point of water is 212 degr F. Even not when filled with 1.4 times AT-pressure D and E load.
Worse it would be if the tire maker upgrade it by 2 steps so here F-load with at-pressure of 110 psi.

Again made picture of spreadsheet I used for it, also at bottom the calculation I used for a post back.

[noteven]

A tire engineer explained the air pressure in the tire carries the load. The tire contains the air pressure, and is part of the suspension of the vehicle (among other jobs it has...) - inflation @ load tables
are there to assist you to set you tire shape so it performs the best for that load.


So, on an air ride coach would you over-ride the factory system suspension pressure and set the air suspension springs at 125psi (system MAX)? Why adjust the suspension air psi for the load?

[jadatis]

Shoe2728 wrote:
I had St 235 80R 16E went to BF Goodrich Commercial T/A All-Season 235 85R 16E GVW of FW is 12000. I have looked for a pressure weight table but mostly all I fine is max inflation rate is 80 psi. I have a 2011 crossroads cruiser 305skp

In next list from goodyear the 80 psi gives fat printed 3042 lbs maximum load. But dont use this list for determinating needed pressure.
Goodyear list only to determine maximum load,
This is for all brands the same so can be used to determine the maximum load of your tires too.

This is between Loadindex 119 and 120 , European system would give it as 119 with 2998 rounded 3000 lbs maximum load.
Will give picture of part of my made extra save pressure loadcapacity lists.



The little lower maximum load of 119 Loadindex is no problemm.
Compare it with the Goodyear list and see the differences .
Here a picture of that list too with again your tires sises highlited.



With your 12000lbs GVW with minimum 10% pinload ( or whatever you call it) I would use this for reserve and devide 12000/4( tires)=3000 lbs a tire ( asuming 2 axles and not dual load).
This would need the 80 psi and for the ST old 65 psi .
Because its about the maximum load of the tires.
You can even add up to 25% for a trailer with no living stock in it, to the real load a tire for reserve and still no bumping so screws tremble loose. This would calculate 12000-10%= 10800/4= 2700lbs+25%=3375lbs a tire wich would need 90 psi with my made list, and is allowed by most tire makers that 10 psi going over AT-pressure.

Ofcource also mind the rimms to being allowed that pressure.
See post above this of mine about it.