Keeping Tires Topped Off

[pmsherman]

My 2011 Georgetown requires 84-86 PSI for the Michelin replacement tires I now have. My 100PSI "hot dog" (shape of the tank) compressor won't fill the tires because with a 100PSI cutoff, the compressor doesn't cut in again until the tank pressure drops to 80PSI.

The compressor has been relegated to the garage and I replaced it with my old Sears 125PSI tankless compressor. I need to run the generator to use it if I'm not plugged in but It does a very quick job of filling the tires. I use a Slime digital pressure gauge and have a TPMS installed that monitors the tires on both the rig and my toad.

Phil

[Tireman9]

Originally Posted by llr

Unless you have a tire / wheel issue they really shouldn't require air during a trip. Checking with a gauge or better yet a TPMS system yes. I do carry a cheap 12V compressor just in case.

the cold tire is specified at a certain temperature (I believe 70) colder it will be a little low and hotter a little high which is expected, I believe 2PSI/10 degrees.

Sorry but "Cold Tire" inflation temperature simply means the tire is at Ambient temperature i.e. not driverfor previous 2 hours and not in direct sunlight for previous 2 hours.


Inflation does change 2% for each change of 10F.


I rely on my TPMS to confirm there has been no significant change in pressure. I do not worry anout +/- a few psi as I run a +15% margin on inflation based on my measured load on my motorhome.


Trailers should run tiresidewall pressure as their cold pressure BUT they should also have a 15% margin of load capacity over measured load.

[BuzzWolfAR]

I carry a pancake compressor as I have a slow leak in a truck tire, and they can't find the cause.

Really like TPMS to track temp and pressure as I drive. I use TST 507 and would recommend them.

[Tireman9]

A comment on TPMS


As a tire engineer, I see little reason to present the temperature of the sensor. IMO this extra information has some problems.

1. Tires fail from low inflation primarily due to air leaks (puncture, cut or valve problems) but not from just getting hot. You only get a tire hot from running too fast and/or running to low an air pressure.

The sensor is not actually reading the temperature of the air in the critical location as the hottest location is interior to the tire construction and measurement of that location can only be measured with a needle probe.

2. The temperature number is distracting and is actually the temperature of the sensor, not the tire and the sensor is cooler than the wheel.

3. The temperature is significantly (25F to 35F ) different than the tire temperature for most applications.


While it is possible for a sensor to report a dragging brake or failing wheel bearing an IR hand gauge is a better tool to use if that is your concern as the hub will be hotter than the wheel and provide an earlier warning.


PS Will be posting this on my RV Tire Blog in prepartionto upcomming report on internal vs External TPM sensor comparison.

[Reverse_snowbird]

Originally Posted by RockyRed

What's the best way to keep tires topped off w/air on a trip (does hand pump work or suggestions on pump ?). Also, what is the most accurate air gauge you have found ? Thanks ! Sorry__fairly new at this.

Hand pumps don't work, but there are a lot of really inexpensive portable tire inflators. Just make certain that it has enough psi to inflate your tires.

We got one that automatically turns off when the preselected psi is reached.

There are two types.... one that operates on electricity is advantageous if you are camped with electrical hookups. With an extension cord, you should be able to reach all tires.

Ones that connect to cigarette lighters can have a couple of problems. Not all vehicles have cigarette adapters. Most newer vehicles will require keeping the truck running to keep the socket active.

There are some that have both connections or an adapter for electric.

I found mine on Amazon.

( TPMS didn't help our friends who lost the tread on their tire. Wasn't hot and didn't lose pressure. )

[llr]

Originally Posted by Reverse_snowbird

Hand pumps don't work...

Hand pumps will work fine, if you are up to working that hard I would not use one unless extremely desperate. Think how long it takes to inflate a bike tire, then multiply by probably 10-100 and see if you want to do it.

[Cypressloser]

The Viair 450P is the best 12Volt air compressor I've seen, it's quiet, runs very smooth, still has a good cfm output at high pressure and has a 100% duty cycle for the largest tires - but not cheap.


I agree with Tireman, carry an infrared thermometer and measure the temperature on the wheel hubs when taking a break. It'll show a bearing going bad long before the TPMS picks it up. The tire temperature can easily differ by more than 20 deg. between the sunny side and the shade side where as the temperature on the wheel hubs doesn't vary nearly as much.

[wildcatter]

Originally Posted by jimmoore13

x-2 on the ViAir.
I have this one.
Key advantages:

• Durable pump...not plastic junk
• Powered direct from battery - not limited to the low amperage available at cigarette lighter

RV tires tend to be larger, and more importantly, they require significantly higher pressures than car tires. A good compressor makes all the difference.

Jumper cables make a great "extension cord" for a direct-to-battery compressor, and the compressor can run off the TV battery or the RV battery bank.

ViAir makes many models, and mine is one of their less expensive quality models.

As for testing pressures, find a good, brand-name tire pressure gauge that is rated for something close to your optimum pressure. My tires require 50 PSI. A 100 PSI gauge is not sensitive enough, and the gradations are too small. A better choice is a gauge that tops out just above your rig's ideal tire pressure, then the gradations will be course enough to give you a good reading.

I just bought one of these myself from JEGS, I should get it tomorrow, I bought it because it looks like it is sturdy.

[Reverse_snowbird]

Originally Posted by llr

Hand pumps will work fine, if you are up to working that hard I would not use one unless extremely desperate. Think how long it takes to inflate a bike tire, then multiply by probably 10-100 and see if you want to do it.

Let me clarify.... a hand pump would not work for me..... not enough strength or patience.

[Murbella7]

Originally Posted by Tireman9

A comment on TPMS


As a tire engineer, I see little reason to present the temperature of the sensor. IMO this extra information has some problems.

1. Tires fail from low inflation primarily due to air leaks (puncture, cut or valve problems) but not from just getting hot. You only get a tire hot from running too fast and/or running to low an air pressure.

The sensor is not actually reading the temperature of the air in the critical location as the hottest location is interior to the tire construction and measurement of that location can only be measured with a needle probe.

2. The temperature number is distracting and is actually the temperature of the sensor, not the tire and the sensor is cooler than the wheel.

3. The temperature is significantly (25F to 35F ) different than the tire temperature for most applications.


While it is possible for a sensor to report a dragging brake or failing wheel bearing an IR hand gauge is a better tool to use if that is your concern as the hub will be hotter than the wheel and provide an earlier warning.


PS Will be posting this on my RV Tire Blog in prepartionto upcomming report on internal vs External TPM sensor comparison.

Even with the spelling mistakes (sorry) this is probably one of the most sensible comments I have read about tyres and the use of TPM's. Thanks.

[hojo70]

[Ebbs]

Originally Posted by llr

the cold tire is specified at a certain temperature (I believe 70) colder it will be a little low and hotter a little high which is expected, I believe 2PSI/10 degrees.

It’s not the air temperature that you’re concerned about. It’s the tire temperature that you pay attention to. Measure tire pressure when the tire is cold.

[LannyCox]

llr mentioned "cold" pressure being at 70º. Now that summer is here in Texas, the low temperature at night is about 77º-80º. By the time I get to my rig to check the pressure, it may be 90º outside.

What adjustment in psi do I need to make?

[jaherbst]

Originally Posted by hojo70

Ryobi makes a larger pump that is a lot faster.

Jack

[Ebbs]

Originally Posted by Tireman9

Sorry but "Cold Tire" inflation temperature simply means the tire is at Ambient temperature i.e. not driverfor previous 2 hours and not in direct sunlight for previous 2 hours.


Inflation does change 2% for each change of 10F.


I rely on my TPMS to confirm there has been no significant change in pressure. I do not worry anout +/- a few psi as I run a +15% margin on inflation based on my measured load on my motorhome.


Trailers should run tiresidewall pressure as their cold pressure BUT they should also have a 15% margin of load capacity over measured load.

My trailer has maximum tire pressure of 80. The label on the trailer says to inflate to 65. I compromised and inflated to 71 on a cold tire. The rest is too technical to worry about.

[Wolverine 1945]

What we saw on our trip to SD a couple of weeks ago was rising temps & rising pressures
No need to add air !!!

[Tireman9]

Originally Posted by LannyCox

llr mentioned "cold" pressure being at 70º. Now that summer is here in Texas, the low temperature at night is about 77º-80º. By the time I get to my rig to check the pressure, it may be 90º outside.

What adjustment in psi do I need to make?

Sorry but llr info is left over from High School Chem class. There is simply no "standard" temperature for setting tire pressure.


You can read post#22 in this thread or read these RV Tire Safety blog posts on the topic.

[Tireman9]

Originally Posted by Ebbs

My trailer has maximum tire pressure of 80. The label on the trailer says to inflate to 65. I compromised and inflated to 71 on a cold tire. The rest is too technical to worry about.

Slight clarification on the sidewall pressure info.


The 80 psi is actually the MINUMUM cold inflation needed to support the RV MAXIMUM load.


Multi-axle trailers should run the tire sidewall tire pressure to lower the Interply Shear forces that are trying to tear the belts and tread off the tire.


Here are some posts on Maximum inflation.


Here are some posts on why Lowering the Interply Shear is a good goal.




Please do not make the mistake of lowering inflation because you think high inflation is the cause of "Blowouts". It just isn't.

Here is info on a tire failure incorrectly called a "Blowout".