Tire Pressure

[norty1]

Originally Posted by Edutron

STOP. Everybody stops and performs tire checks to maintain proper tire pressure. I'm not here to argue. Do what you will with your tires, its your money. I have zero problems - ZERO and with TPMS, I do stop if tire pressures are rising and do release to correct pressure. My tire my money, and your safety. Now, try and get everybody else to perform tire checks to be more safe for you.

I stop and look at my tires but I have never ever heard of anyone adjusting pressure when hot until now. Read up on recommendations from tire manufacturers.

[Edutron]

Originally Posted by norty1

I stop and look at my tires but I have never ever heard of anyone adjusting pressure when hot until now. Read up on recommendations from tire manufacturers.

I'll help you. Mfg's RECOMMEND mens - shoulda, coulda, woulda. Truck drivers perform tire checks 24/7/365. In fact, over-inflation can get you a citation. I understand an RV most often is not commercial, but as an example - my Pinnacle empty with 3 propane tanks weighs in just under 13,500 lbs which pretty close to an empty weight 53 foot DOT van trailer. If you blow a tire and that tread shoots through a windshield its all on you (personal injury, property damage) besides the damage and people blow tires everyday for not performing tire checks and adjusting tire pressure correct. With this said, yes, I have a CDL-A with a retired accumulated mileage of about 3.2 million miles which is not that much compared to others with no accidents, 3 flats, one blow right center axle outer recap trailer tire hauling heavy at 105,000 lbs in 95 degree temps in Wy. on I-80 many years ago (PITA). Most people run China bombs at that which is a SIN. Like Aviation, the Mfg recommends because its a liability issue with the factory not a liability issue with you because they don't care about you. Me, I don't care what other people do only what I do. ENJOY.

[White Ox]

Rule of thumb....

Tire pressure will increase roughly 1psi for every 10deg. F increase in temperature applicable to passenger car tires typically around 35psi.
Tire pressure will increase roughly 2psi for every 10deg. F increase in temperature applicable to higher pressure tires on rec. vehicles, busses, trucks, etc.

Scenario:
Tire COLD pressure set to 80psi on a 70deg. F morning. Start Trip
Drive into 100deg. F weather and you've increased the ambient air by 30deg. F. So that's a 6psi increase ONLY from the outside air temperature. Add in friction, blacktop temperature, etc....and you could easily see 110 - 115 Deg. F. - so now we're up to 9 psi increase to 89 psi. YMMV slightly.

I've only witnessed the TMPS on my truck and the pressure readings pretty much follow the 2psi rule as they are inflated to 65psi (when not towing) and the rears @ 80psi when towing.

The aftermarket TPMS on my Camper is the Smart TPMS by Minder Research. I can say, I'm pretty disappointed in the repeatability between sensors. I've got 6 sensors and I won't use 2 of them because their numbers are just way the hell wrong. 3 of the other 4 are very consistent, but are off 5psi from multiple pressure gauges that I use (the gauges are all within 1psi of one another). But one has to remember, the TPMS shouldn't be used to tell you the cold set pressure, it's to monitor it for quick changes in pressure as well as high temperatures while under way. That 4th sensor always reads 10psi lower than the other 3 when I first start a trip, and after about 10 mins on the road, somehow figures out it's supposed to be 10psi higher and starts reporting a more accurate number.

[JohnWedell]

So based on what said here my Goodyear endurance tires on my Northpoint should only be filled to 50 psi Based on the chart.

[GHen]

Since tire pressure is a safety issue it’s important to avoid opinions. Here are some links from the Goodyear website. There are some statements that even surprised me…

https://www.goodyear.com/en-US/learn...e-cold-weather

https://www.goodyear.com/en-US/learn...e-air-pressure

https://www.goodyear.com/en-US/learn...-tire-pressure

You should read these and their links for Goodyear tires.
Here are a few key statements, but there are many more that should be read since they may be considered out of the context of the statements on the website.


“Note: It’s important that tire pressure is checked while the tires are cold, which means the vehicle has not been driven for a minimum of 3 hours, and ideally the tires are kept in a shaded area.”

“Goodyear recommends that tires be inflated to the vehicle manufacturer's recommendations as found on the Vehicle Tire Information Door Placard or the Vehicle's owner’s manual. The placard can be located on the door edge, doorpost, glove box, or fuel door. The recommended PSI should not be confused with the maximum cold inflation pressure that the tire is rated to hold, which is found on the sidewall”

“One place to not look for the vehicle recommended tire pressure is on the sidewall of the tire. There will typically be an inflation pressure listed on your tire – but that pressure is the maximum inflation pressure for the tire, and not the pressure recommended by the vehicle manufacturer.”

“Just as colder weather can cause PSI to drop, excessive heat can cause your tire pressure to temporarily increase. For every 10 degrees of increased temperature, your tires can be expected to increase by 1-2 pounds of pressure”

“Tire Cool Down. Proper tire inflation should be checked when the tires haven’t been driven on for several hours and have had time to cool down”

[Jagiven]

Originally Posted by Springhook

So now I am confused. I run Sailun S637 ST235/85R16. Max pressure 110psi at 4400lbs. I last scaled 11680 lbs on both trailer axles. 11680 divided by 4 = 2920 lbs per tire. My load chart:

https://fifthwheelst.com/documents/C...T-Modified.pdf

sez 55 lbs psi per tire. Can that be?

Springhook, Your numbers look about correct. About 20% of your GVW is on the tongue and not on the tires. Per Jayco's Specifications page, fully loaded I would expect each tire to be carrying about 3300 lbs. Empty (brand new) about 2763 lbs. So pending on how you are loaded, your within a reasonable range. I was not able to find the document you link to, but 80 psi for a fully loaded trailer verses 55psi for your weight seems reasonable.

Overall there is some good and bad info on this thread. Typically you should run the max cold pressure your tires and rims are rated for. Best time to take this measurement is in the morning before you hit the road. As you are driving if one tire is spiking or dipping, it is well worth stopping and checking your tires. If one side is higher than the other side?? where is the sun? Sometimes the road crown/condition can have an effect too.

Your rims should be stamped with the max rating. Unfortunately it maybe on the inside of the rim. But you may also find it stamped behind one of the spokes. Typically, you want to run the max cold tire pressure on a trailer tire. But if you go up a load rating or two, and run max tire pressure you may get more trailer bounce, as the sidewalls are not flexing as much. Good for tire life, bad for all your stuff rattling around inside the trailer.

Just remember cold pressure is what you are looking at each morning, even says that on the side of the tire. As the tires flex, scrub the pavement, this creates friction which creates heat. With some TPS you can see temperature and pressure, you may notice if you are traveling, the shady side of the camper may have lower tire pressures and temperature than the sunny side. This is OK, and normal. If all the tires are behaving the same you will be ok.

Under inflated tires for your load, is a bad thing, as this causes more sidewall flex, hence more heat, and shorter tire life. Hence 55 psi, for your load maybe just fine. You just do not want to start your day at a lower pressure. Also you do not want to add any additional items into the 5ver, without adjusting the air pressure up too. It is better to run your tire pressure at the upper end of your limit, than to low.

Hope this helps

Generic tire pressure chart for load ratings on a tire of your size; https://tirepressure.com/st235-85r16-tire-pressure

[White Ox]

Originally Posted by JohnWedell

So based on what said here my Goodyear endurance tires on my Northpoint should only be filled to 50 psi Based on the chart.

There are tons of misconceptions that started with "safe practices" at tire shops. When a tire shop puts tires on someone's camper - they don't know what the actual rig's weight is, nor how the customer has it loaded - so it's pretty difficult to go to the load table to determine what the "COLD" inflation pressure should be. It's a little OVER inflated vs. UNDER inflated - as underinflation causes more heat, and thus a blowout sooner. So what do you think they tell the customer?

The ONLY guaranteed way to know what weights your rig's tires are seeing is to weigh it with how you tow it. All your gear, all your fluids (beer and other adult beverages included), all your groceries, clothes, EVERYTHING. After weighing, you have the information to head to the load tables. If you want to error on the side of caution, you can overinflate a little as again, better to be over than under.

The same load tables can be found for OTR (Over the Road) Truck tires - and a CDL driver should know this. But often times, their cold pressures are set on empty trailers.... or they have no true idea of the weight they are hauling till they have to hit a scale - at which point, they should adjust pressure. Often, they will inflated to MAX allowable load. Then of course, there are some guys that will haul over max allowable load, and to keep the tires from squatting, will overinflate - which is a bad recipe.

Load tables are there for a reason, and they were created by the engineers that designed the tires.

[White Ox]

Originally Posted by Springhook

So now I am confused. I run Sailun S637 ST235/85R16. Max pressure 110psi at 4400lbs. I last scaled 11680 lbs on both trailer axles. 11680 divided by 4 = 2920 lbs per tire. My load chart:

https://fifthwheelst.com/documents/C...T-Modified.pdf

sez 55 lbs psi per tire. Can that be?

Actually, no, you should run 60psi... if you divide 11680 by 4, you get 2920. If you look at the chart you provided, 55lbs only gets you to 2910 - and thus, underinflated ... and your tire gauge is likely off by a psi or two (as most are). I would error on the side of caution and go up a little.

The other thing to ask yourself is... am I heavier than when I last hit the scales?

[Cincinnati Kid]

I only check the tire pressure cold, out of sunlight. I set it to 80 lb, as Jayco directs for these tires, which in this case happens to be the max sidewall pressure.
The pressure goes up when driving. That is normal and already figured into the recommended cold inflation pressure.

The only time I will change the pressure is when the outside temp changes a lot.
If I fill up the tires when it's 40 degrees outside then drive to a place that's 80 degrees, I'll adjust the pressure as soon as the tires cool down for 3 hours, out of the sun.

But I'm not going to let air out of my tires at a rest area when they are hot. There is no way to accurately gauge your tire pressure when hot. Maybe that's different for tractor trailers, but for us, all manufacturers and tire companies I've seen say the same thing- Inflate cold. Check cold.

[Springhook]

So, I spoke to a Mr. Alan Eagleson of Sailun Tire. He confirmed my thoughts. According to the load chart AND based on my scale weights, my tire pressure should be between 55 and 60 psi. He suggested 65 psi based on the fact that I weighed without water and I will be bringing fresh water in this long trip. (I just was feeling uncomfortable with the 55-60 psi cuz my previous "E" load tires called for 80psi. Now I understand.)

PS: Alan's number in Toronto is 416 315-9391 . A really nice guy.

[Rock]

I ordered mine with G rated tires. Goodyear G614 RST LT 235 85 R16. Been running 95 psi and getting even wear. Sticker says run 100 but that is for max load. I have the 5500 Onan and sticker says full propane and gas 13,741 add water 721 lbs more. I run with a lot packed inside FW. Have to have about 20k on tires and like I said wear is even. I run my truck on tire wear for psi also.

[jasum]

It does NOT matter what your fifth wheel sticker says. Sticker was for the junk China tires that were on it.
IF your new tires are rated for 110psi, when tires are COLD. 110psi is the most air you want in them.
I have Goodyear G614 tires on mine, 110psi when COLD.
I run anywhere from 100psi to 105psi in them. Only check when tires are COLD.

Yon can call Tredit Tire and Wheel and check on your wheel rating. Mine were rated for 110psi in tires. I believe yours will be too, but you may want to double check.

[imjustdave]

Overthinking ... about overthinking.

80-100 seems like a good number set it and forget it.

If 1 goes way up... maybe a brake is dragging. if 1 is dropping you have a leak.

Past that enjoy camping, you will never tow it long enough 100k+ miles to wear out the tread or maybe you will but very few of us come close.

[jasum]

Originally Posted by norty1

Agree. cold is cold. They heat up when running. TSPS will monitor but stopping to let air out? Do some research first before giving bad info.

Edutron your next post is also bad info. Tires are engineered with that temp increase taken into account providing you start out with the correct pressure.

X2

[Peoples16127]

If you think of this problem as a load capability of the tire envelope, it takes a certain amount of air pressure and volume to support a given weight. Think of this in terms of a balloon, a larger balloon will support more weight than a small a balloon when inflated to the same pressure. The stiffness of the tire is a small consideration in the load carrying capability of the tire. If you are not changing tire size, the wall thickness of the tire should have only a small impact on the load carrying capability of the tire, the biggest impact is tire pressure.
That is a long winded way of saying that tire load capability is mostly a function of tire pressure.
FWIW in my poor days, it was common to put an underrated tire on a wagon and put more than rated tire pressure to be able to carry the necessary load.

[riddleswest]

Excellent informational chart! Thanks MrSaxy.
The people who are saying the the cold PSI is not what you set your tires to are absolutely wrong. I've been a professional technician for nearly 30 years. That rating is what the tire is designed to run at when loaded and when up to temp. Yes the pressure will go up, but as others have said, that is what its designed for.

[Marmot]

Originally Posted by Edutron

First off, 80 psig is not cold pressure, use that as running pressure. I set our tires (Pinnacle at about 70 psig cold. By the time you run up the highway about 50 miles (summer) chances are your trailer tires are at or above 80 requiring a stop to relieve pressure. TPMS on every wheel is mandatory if you don't want to blow tires. This is the reason why so many have tire blowouts - running to high pressure and too fast.

Will all due respect, all of this post is wrong. Do not follow his advice.

[Marmot]

Originally Posted by jasum

X2

Yes, ignore the terrible advice please

[Marmot]

Originally Posted by jasum

It does NOT matter what your fifth wheel sticker says. Sticker was for the junk China tires that were on it.
IF your new tires are rated for 110psi, when tires are COLD. 110psi is the most air you want in them.
I have Goodyear G614 tires on mine, 110psi when COLD.
I run anywhere from 100psi to 105psi in them. Only check when tires are COLD.

Yon can call Tredit Tire and Wheel and check on your wheel rating. Mine were rated for 110psi in tires. I believe yours will be too, but you may want to double check.

The sticker on the RV must be followed no matter what brand tire is mounted. Please stop giving your terrible advice.

[fr8erfxr]

Originally Posted by Edutron

I'll help you. Mfg's RECOMMEND mens - shoulda, coulda, woulda. Truck drivers perform tire checks 24/7/365. In fact, over-inflation can get you a citation. I understand an RV most often is not commercial, but as an example - my Pinnacle empty with 3 propane tanks weighs in just under 13,500 lbs which pretty close to an empty weight 53 foot DOT van trailer. If you blow a tire and that tread shoots through a windshield its all on you (personal injury, property damage) besides the damage and people blow tires everyday for not performing tire checks and adjusting tire pressure correct. With this said, yes, I have a CDL-A with a retired accumulated mileage of about 3.2 million miles which is not that much compared to others with no accidents, 3 flats, one blow right center axle outer recap trailer tire hauling heavy at 105,000 lbs in 95 degree temps in Wy. on I-80 many years ago (PITA). Most people run China bombs at that which is a SIN. Like Aviation, the Mfg recommends because its a liability issue with the factory not a liability issue with you because they don't care about you. Me, I don't care what other people do only what I do. ENJOY.

I was going to stay out of this one...not here to argue, but...
Since you brought up aviation, I've been a commercial aircraft mechanic for 35 years and all tire pressures are adjusted when COLD. When tire pressures are checked after a flight, the temps are 30-40 psi higher than cold. You NEVER let nitrogen out of the tires when they are hot. You basically are checking that the tires are all within a few degrees of each other. Tire manufacturers account for this. This is my experience from reading actual documentation from the manufacturers. You can do as you please, that's your perogative, just bad advice for the people here seeking advice