Tire PSI - Cold vs Hot

[No1Hunter]

Originally Posted by creativepart

I don’t know the direct answer to your question and I’m not sure Travel Trailers have tire inflation stickers... but when I had TTs I was told to run the tires at the max pressure printed on the tire sidewall. For me that was always 80psi, but your tires may be different so you should check.

The cold tire pressure (cold=not having been driven) is all about weight carrying capacity. And that max tire pressure on the sidewall is the max weight carrying number as well.

I looked in your Operators Manul and under tires it says :

I hate to resurrect part of an old post (it was too old to post to) but I have a couple question that I can't seem to find a straight answer to.

First - What is the Max hot pressure? I understand filling the tires to Max COLD pressure. But as we all know, once you start driving, the temp goes up in the tire which, in turn, increases the air pressure in the tire. In no time, the tire will be over the Max air pressure. In my case, if I remember right, was around 5 to 8 psi.

Second - Once you start driving and see that your tires are over the max air pressure, do you stop and let air out, or do you try to guess what the "Hot" pressure will be and start out at that level?

I asked my dealer about this when I picked up my TT a couple months ago and though he didn't actually directly answer the question (liability issue??), he more or less indicated the tires should never exceed the Max air pressure.

Having Castle Rock tires still on my TT, I don't want to blow them up. Tags says 80psi

[creativepart]

The easy answer is there is no max hot temp. Which is why you find the cold pressure setting everywhere and the hot pressure no where at all.

Of course, there are exceptions. The first of which is that if you have a failed wheel bearing temps can get outrageously hot - enough to catch things on fire. So, of course that's not good. But other than that then important number is the cold pressure.

Cold... as in not having been driven (or less than one mile). If it's 45 outside or 85 outside doesn't matter. This undriven pressure is what you want your "cold" pressure set to.

After that, you need not worry what the temp is when you're driving 60 mph and 60 miles down the road. So, no, you don't try to maintain that "cold" pressure all the time. Just before driving. Don't be obsessive about it. Before going on a trip - check the pressure and get them aired to the max cold psi. Then enjoy your trip.

Yes, they will increase as much as 15+ degrees but that does not matter. Just touch your hubs and wheels when you stop for fuel or lunch to insure that you don't have a bad wheel bearing.

You may want to invest in a TPMS - tire pressure monitor system. You screw sensors onto your air valve stems and place a monitor in your tow vehicle. That will show you both psi and temperatures of your tires.

I have these on my motorhome - but I never even considered it for my travel trailer when I had one. It's up to you.

[No1Hunter]

Thanks for the reply. It is a little unnerving watching the TPMS show the air pressure increasing going down the road, especially with the Castle Rock tires!

Oh, and yes, I touch the hubs every stop to see if there is an issue. I learned that years ago after having a major tires store place the brakes on a large boat trailer only to find out they didn't adjust them correctly, so the pad were rubbing. 40 mile later I was under the trailer, backing them off, so I could complete my trip.

[anewrver]

Saw this and thought about the tpms monitor and like the idea of it on the trailer. How do you handle it if your tt tires were nitrogen filled though? Still check pressures as usual, but if for some reason its gets low youd have to find somewhere tht does nitrogen for the tires correct?

[No1Hunter]

I suppose you could look around and find someplace that has 100% nitrogen. My tires came with nitrogen but currently have a mixture (mostly nitrogen). Keep in mind, good old "air" is roughly 78% nitrogen, 21% oxygen and 1% other gases.

[reeman]

Thanks for the reminder to purchase an infra red thermometer! One of the most important things hauling any thing heavy on bearings with rubber tires is to check for overheating. An infra red hand held is a very quick way to check going down the road especially when it is a hot day.
As it is I have been using my hands and it is very difficult to ascertain hub center temperatures in relation to brake drums. With a hand held one should be able to detect excess heating in the center of the drum at the spindle. Or get a better sense of what the tires are doing on long hauls.
Keeping the pressure up is extremely important but also checking for overheating of loaded wheels should be part of the routine for going down the road with any driver.

Here in the mountains of BC doing thermal checks on the running gear is essential, it is a good habit to check as frequently as good professional drivers do when hauling loads.

[No1Hunter]

Thanks for the reminder to purchase an infra red thermometer!

Harbor Freight Tools has one on sale for 15 bucks (40% off), with a coupon on their website.

[reeman]

Originally Posted by No1Hunter

Harbor Freight Tools has one on sale for 15 bucks (40% off), with a coupon on their website.

I think I will get a little better one for about 80 Canuck bucks.

Our trailer is single axle so checking tires is crucial for safety reasons. Our tires are rated to 4080lbs for the axle. So with an average 2900-3000lb axle load it means that we are well within safety margins if the tires lose a little inflation in the cold. I only get concerned if they drop down below 55 psi as they are rated for 60 psi cold.

If someone has a trailer with the stock 14 inch load range C tires then making absolutely certain they never drop below about 48 psi seems to make sense as the six ply radials are rated for 50 psi cold and in a pair their load rating actually tops out below the gross of the trailer at 3520 lbs.
Safe to a certain extent but not safe at all if they are underinflated or heated by overloading or driving in hot conditions at high speeds as some people do with these trailers!

A few of the trailer companies were shipping the trailers stock with this low a spec on the tires. I will say that Winnebago wised up as did Forest River on this issue though and now spec the equivalent trailer to ours as requiring load range D tires.

In short paying very careful attention to your tires when hauling a load at close to 70 percent of the tire carrying capacity of any vehicle is the only sane way to go down the road.

[Marine359]

If you inflate your TT tires to cold pressure rating, you’re good to go. The tires will heat up underway, and tire pressure will increase. That’s normal. Typically, you should set high pressure alarm on your TPMS at 10 psi over cold inflation pressure. It’s more critical if tire pressure decreases 10psi below cold inflation. If the low pressure alarm on your TPMS goes off, pull over immediately and find out what’s causing the problem.

[reeman]

Originally Posted by Marine359

If you inflate your TT tires to cold pressure rating, you’re good to go. The tires will heat up underway, and tire pressure will increase. That’s normal. Typically, you should set high pressure alarm on your TPMS at 10 psi over cold inflation pressure. It’s more critical if tire pressure decreases 10psi below cold inflation. If the low pressure alarm on your TPMS goes off, pull over immediately and find out what’s causing the problem.

I am a little skeptical about the accuracy of TPMs being that good. To my understanding the low tire alert system can be set to indicate a drop but not that finely graduated. We had a car with TPM and it didn't go off until it was obvious that the tire was down by looking at it.
Radials can be deceiving by looking as we all know and from what I hear about add on remote TPM for travel trailers they can be flakey and should not be relied upon except as an extreme warning system. Which is a good idea to have a fire alarm that goes of if a tire is about to go flat, but in my experience nothing is better than using your hands, eyes and an an accurate tire pressure gauge regularly with heavy loads on anything on rubber wheels.

IMO the habit of checking inflation, temperature and tire condition accurately with a good gauge regularly is the best way to be certain about the safety of your running gear. There is no substitute for checking tires for correct inflation, bulges and damage and overheating going down the road.

[No1Hunter]

The idea of using a TPMS is detecting a leak while you are driving. If you feel the need to check the air pressure with a "good gauge" while rolling down the road, good luck!

[Marine359]

Originally Posted by reeman

I am a little skeptical about the accuracy of TPMs being that good. To my understanding the low tire alert system can be set to indicate a drop but not that finely graduated. We had a car with TPM and it didn't go off until it was obvious that the tire was down by looking at it.
Radials can be deceiving by looking as we all know and from what I hear about add on remote TPM for travel trailers they can be flakey and should not be relied upon except as an extreme warning system. Which is a good idea to have a fire alarm that goes of if a tire is about to go flat, but in my experience nothing is better than using your hands, eyes and an an accurate tire pressure gauge regularly with heavy loads on anything on rubber wheels.

IMO the habit of checking inflation, temperature and tire condition accurately with a good gauge regularly is the best way to be certain about the safety of your running gear. There is no substitute for checking tires for correct inflation, bulges and damage and overheating going down the road.

Agree. Always check with gauge before departure. The TPMS doesn’t need to be incredibly accurate. Most have monitor displays of tire pressure. Heck, that’s all you need. If you see a pressure 10 psi under, pull over to figure out what’s wrong.

Nothing is better than checking tire pressure with a gauge. But when underway, you can’t check with a gauge. Start out with cold inflation specs. Then use TPMS to tell you when something is amiss.

[Morich]

The value of TPMS is that it is a full time watchman over things you will never really do often enough.
If you go through a construction zone that goes for 20 miles, is anybody actually going to stop to see if they hit a rebar in the first mile? NOT!
But if you have a TPMS, it will cycle through all the tires and give temp and pressure on each. If you have the alarms set even half way right, it will give you a notice that one tire is doing soemthing odd and it will be a lot quicker that you waiting until you stop for lunch or gas, etc.
Look at real drivers and their trucks? You are very likely to see they run TPMS as they know how quick things go downhill!
A couple hundred dollars too much? Try paying for a repair if the tire blows, wraps around the brake lines and then goes out through the trailer sidewall! That is when the few bucks upfront becomes really cheap!

Kind of like wearing a life jacket when you go out on the water ---even if you don't plan to get in the water!

[No1Hunter]

Yup, the TPMS does not take the place of initial prep for your trip, both going and coming home. Just like your engine oil gauge doesn't take the place of pulling the dipstick. However, if you are driving down the road and notice your oil pressure drop to zero, it is best to pull over ASAP.

[wyocamper]

Originally Posted by reeman

I am a little skeptical about the accuracy of TPMs being that good. To my understanding the low tire alert system can be set to indicate a drop but not that finely graduated. We had a car with TPM and it didn't go off until it was obvious that the tire was down by looking at it.
Radials can be deceiving by looking as we all know and from what I hear about add on remote TPM for travel trailers they can be flakey and should not be relied upon except as an extreme warning system. Which is a good idea to have a fire alarm that goes of if a tire is about to go flat, but in my experience nothing is better than using your hands, eyes and an an accurate tire pressure gauge regularly with heavy loads on anything on rubber wheels.

This is a completely invalid comparison. The minimal system on many cars just alerts when one tire pressure is low, but not which tire, based on rotation speed detected by the ABS system. Some manufacturer and most aftermarket TPMS systems have sensors on each tire and detects the tire pressure and temperature in real time and displays it on the monitor. A TPMS system is virtually the same as having an accurate tire pressure gauge attached to your valve stem while you drive down the road.

And unlike valve stem sensors that "wake up" when they start rolling, an aftermarket TPMS sensor is always on, and allows you to check tire pressure from the comfort of the driver's seat before you hit the road.

[thompwil]

Originally Posted by wyocamper

This is a completely invalid comparison. The minimal system on many cars just alerts when one tire pressure is low, but not which tire, based on rotation speed detected by the ABS system. Some manufacturer and most aftermarket TPMS systems have sensors on each tire and detects the tire pressure and temperature in real time and displays it on the monitor. A TPMS system is virtually the same as having an accurate tire pressure gauge attached to your valve stem while you drive down the road.

And unlike valve stem sensors that "wake up" when they start rolling, an aftermarket TPMS sensor is always on, and allows you to check tire pressure from the comfort of the driver's seat before you hit the road.

Been using the TST system for five years now. I have verified the sensors accuracy against gauges and have determined they are as accurate as both my digital gauges. Yes, I use them to verify tire pressures before departure and adjust if required, very convenient and saves time.
The TST system will alarm a leak before it hits the low pressure setpoint, likely using a derivative of the rate of decreasing change from current levels. Yes, it does work as I got a leak alarm on the toad before it reached the low alarm setpoint. Removed a drywall screw, plugged it and back on the road.
EDIT: My data sticker lists tire pressures at 82psi, I've been running 87psi. On hot days my pressures have increased to as high as 109psi. I've reached out to the tire manufacturer some time ago asking about normal expansion pressures, and never received a reply.

[Morich]

One of the things using TPMS will likely do for you is make you less nervous about what to set the prtessure as you will se how much it varies and why!
Jus the simple act of parking is often going to chang ethe tire pressure if one side is inthe sun and the other not!
That's where I find it totally bogus to say that we can just check the pressure and be safe!
Every time we change direction of travel the pressure may change, so the idea that we can actually set them at any specific PSI and expect to drive 20 miles and it still be the same is just not what we find!
I now worry less about the pressure when I start because I can look at a monitor and see what it is as we get 10, 20, 100, miles down the road.
Nobody really gets out and checks there tires nearly as often as a full time monitor will!
I can look at the monitor with a quick peek and see what each tire is doing on temp and pressure but I lost interest after a few trips as it was not information that meant anything as long as it stayed within range and I knew it would alarm when something worth looking happened!
Just slightly better than stopping every few feet to check the pressure but better because you get a reading of temp and you get down the road a whole lot quicker!

My grandma used to use her hand to check our temperature but I never really felt like she was as good as a thermometer and I'm sure she can't test tires while running alongside!

[RocknRoll]

For what it's worth, IMO, the 50 lbs. cold (for my tires) is NOT a hard number. There are multiple factors that should be taken into account. Before a road trip I'll do a complete tire inspection checking for cracking, tread abnormalities and finally a pressure check with a gauge taking into account what the temperature swing may be that day.

This time of the year, especially in the SE, you can still have very chilly mornings and by mid-day the outside temperature can increase 40 degrees or more. I'll also determine the type of road/highway I'll be traveling. Faster you go, the higher the temperature will be. For example, yesterday morning I set the pressure for 47 lbs. and it got as high as 52 lbs. by 2:00PM which is my personal happy zone.

I've found that my TPMS has been extremely responsive and accurate to the point where I'll see a difference in pressure when driving due to weight distribution and/or temperature, including what side of the trailer is facing the sun. I let it do it's job as intended.

While pressure is important, performing proper maintenance will help minimize a blowout event. Every year I've balanced, rotated AND repacked the wheel bearings. I also protect the sidewalls with a homebrew UV protector. I have 20k miles in almost 3 years on these tires and they still look new.

On a final note, I use www.ventusky.com for my weather forecaster. Check it out!

[reeman]

Thank you guys for letting me know that the newer tpm systems are better than they were.

Unfortunately I will need to use the screw on valve cap variety. Or get them install in rims like an OEM new car which is problematic on an old 2016 Winnie Drop trailer. Then use a repeater to see the rating in the cab of our truck or our car. The car might not need a repeater but the longer wheel base truck most likely will.
I will be looking into the costs of new rims with tpms installed the next tire change on our Winnie drop.

Tire guys tell me that the number one source of tire leaks is valve stems around the rubber where the stem is stuck into the hole on the rim especially on vehicles that sit.

So checking the valve stems with a spray bottle of water and a drop of sunlight liquid is still a very good way to keep in touch with tire pressure problems as well as the only way to check for slow rim seal leaks.

As all have stated TPMs certainly make the most sense when it comes to safety incase something going down the road causes tire failure. But the number one reason for tire failure is failure to check tire pressures and condition before turning the wheels.

TPMS are a great safety feature certainly; but also not being in a hurry to get places and stopping regularly to check running gear especially with a single axle rig is the best way to remain safe going down the road IMO.

[No1Hunter]

Tire guys tell me that the number one source of tire leaks is valve stems around the rubber where the stem is stuck into the hole on the rim especially on vehicles that sit.

When I get my tires changed out, I will insist on metal valve stems rather than rubber. They are much better. In fact, if you use the TPMS flow-through senors, they are required.