Getting accurate tire pressure readings - RV-Dreams Community Forum

Camper Chronicles · RV-Dreams Family Member

Getting accurate tire pressure readings

RonC · RV-Dreams Family Member

I have a Viair RV air compressor which has a trigger handle with a gauge ... which is what I use and assume that it's accurate ... but certainly not guaranteed. It does agree with my TST 507 TPMS so at least they validate each other. TST recommends the alarms be set at 10 psi below and 20 psi above the cold pressure settings. So a 30 psi rise would cause a pressure alarm, assuming you start out at the correct cold pressure setting. When you start out at 34 degrees ambient, is your cold pressure set correctly? I ask, because if you start out under inflated then you will generate additional heat and pressure. I typically see tire pressures running about 15 psi over my cold pressure. My tires are set at 105 psi cold so I see 120 or so during the heat of the day at highway speeds. With regard to your questions about tire temperature ... TST recommends setting the alarm at 158 degrees. They say that temperature related blow outs occur between 180 and 200 degrees. My tires seldom see any thing higher than 20 degrees over outside temperature, but have occasionally gone up to 25 or 30 if the sun is shining hard on one side. I have never had a temperature or pressure alarm using these settings.

-- Edited by RonC on Wednesday 21st of September 2016 04:14:15 PM

Clay L · RV-Dreams Family Member

At a rally Michelin had a big tire/wheel filled with air and a tire gauge that was calibrated and certified. They would check your gauge against the tire. The problem is getting access to a calibrated/certified gauge. Suspect they are expensive.
I found this one HERE and as you can see it is expensive - $299.

-- Edited by Clay L on Wednesday 21st of September 2016 11:28:56 AM

RonC · RV-Dreams Family Member

That's a pretty expensive tire gauge alright. I doubt I'll ever own one of those.

Rickl · RV-Dreams Family Member

Most quality tire shops have a "master" gauge and would check your gauge for accuracy. If your present shop doesn't have one I would run! The other thing you can do is check your gauges pressure reading against 3-4 others on the same tire. A large truck tire will suffice as opposed to a smaller tire with less volume. If all 3-4 are within 1psi then you can safely assume the accuracy.

MarkS · RV-Dreams Family Member

Accuracy is always nice and I would look for a way to confirm the accuracy of my gauge but, I wouldn't loose any sleep in the meantime. If you are within 10 pounds and checking with a gauge you are already doing more than most. Do the best you can, set up your TPMS, continue to look for a way to check your gauge for calibration. You deserve a medal for caring in the first place.

CJSX2fromCT · RV-Dreams Family Member

Great question Lee, I do 2 things. I set my air compressor gauge (output) to 80 lbs for the truck and 100 lbs(G114's) for the trl. I then check with only one air pressure gauge. (Heavy Duty Straight Foot Dual Head) I "use" to check it with multiple gauges and like you got different readings. My left rear trl tire runs higher pressure and hotter then the other 3 I have noticed, so what I do is I drop that one down 5psi knowing it will gain it back and it does while running. I believe it is on account that is the side our kitchen is on. I have my monitor set at 100psi for low and 125psi for high, at this time I am only running sensors on the trl. Hope this helps you. Safe travels ahead.

Rickl · RV-Dreams Family Member

10 psi can mean a significant amount of carrying capacity depending on the size of the tire. Be cautious. Also, you should always set tire pressures when the tire is "cold". That means that the tire hasn't been run and is sitting at ambient air temperature. Once set leave the pressure alone during the day. Yes you may see an increase as the temp warms up and depending on the static load the tire/wheel assembly is being asked to haul.

That is why it is so important to KNOW your individual wheel position weights. Don't panic if you get an increase in pressure that stabilizes. However if you are driving and the pressure spikes it is a good indication that you probably overloaded as a result of loss of pressure.

When you get a leak the pressure will drop obviously, but continued driving heats the tire up increasing the pressure. At that point two things can occur, first a "blowout" as the pressure generated finally exceeds the limit of the tire of your tire is so hot it starts to delaminate. Delamination is essentially reversing the vulcanizing process of the tire. Those are the pieces you see on the side of the highway.