Community Forums

Gary.Jones · 07-07-2019, 07:25 AM

yep, you have got it right. dont worry about a few degree differences on morning temps check to ensure you have these pressures, but then largely forget tire pressure issues until you get to winter and then adjust, but should be good to go!

Gary

rrtribble · 07-07-2019, 08:01 AM

The first thing I did was get my '07 4 corner weighed. Couldn't find any RV dealer local to do this so stopped at the State Weigh Station outside of town and asked for assistance. I was luck that day as they were hosting the current class of State Troopers so when I explained what I was needing and knowing that the State Police often do roadside weight checks I was given the number of the local IOP garage. When I called they told me to come on out and they would do the 4 corner weighing for me. Might work for others too.

QUESTION: Based on all the info shared here and at other sites - Living in central IL I set my psi based on the 4 corner weight and check it before each trip. realizing that tire psi rises with the temp DOES IT DROP when temp goes down? If I start out in IL and go to the Rockies seeing a 40* drop do I need to readjust or just check psi and adjust to keep COLD PSI at setting? Do I then leaving the Rockies and heading home do I need to check PSI and adjust as necessary OR WILL there be any difference?

Thanks is advance - Richard

richard5933 · 07-07-2019, 08:30 AM

Tire pressure should be checked when the tires are cold. That basically means that the tire is the same temperature as the ambient air temperature (not driven on for a few hours and not in direct sun.)

Pressure will go up and down a few psi as the ambient air temperature changes. The larger the change in ambient air temp the larger the change in psi.

You will need to check & adjust as the seasons change.

Podivin · 07-07-2019, 08:36 AM

Quote:

Originally Posted by buck58

2018 Aspire: setting tire pressure this am, in Florida. Even at 7 AM the temperature is between 73 and 75, depending on which side of the coach you’re on, based on the weight of my coach I should have 120 in the front and it says 75 in the back but I’m putting 85... But with it being so warm is that still accurate?

0 degrees, 30 degrees, 50 degrees, 100 degrees - it doesn't matter what the ambient temperature is. Check the tires when they are 'cold' (at ambient temp - not been driven yet that day) and set the pressure to what you've determined will be your running pressure.

Gary.Jones · 07-07-2019, 01:39 PM

Well, in point of fact, ambient temperature DOES make a difference. It makes a very big difference in something like a car tire.... it makes a difference for our coach tires, but less relative difference on a 120# 365 tire than a car tire. The biggest change for car is the difference between summer and winter or Florida and Colorado in the winter. My car tires will change maybe 5 psi and will set off my tire pressure monitors advising me of low tire pressure if I dont add additional pressure to the car tires at the beginning of the winter or the first really cold snap. However, once the tire pressure is set for typical winter temps, then I dont touch them again until spring/summer or significant warm ups. And my strategy works very well with the TPMS because I dont get warning of either high or low tire pressure on normal changes or drives during the winter or during the summer.

The change is less evident on a truck/coach tire. I generally dont do a lot of traveling in snow or very cold Norther temperatures.... my strategy is to avoid the cold by going where it is less cold. However, I set my coach tire pressures based on my 4-corner weights and my typical loaded coach loads, and for all intents and purposes, dont worry too much about them after they are set except to watch the temperature in the morning before any travel (what they call the cold temperature) or while on the road. My Valor TPMS system is set for I believe a 20% rise and a 15% fall (maybe 12.5%) before triggering alarms and once I got the tires set to the proper level for my loads, I have not had to change them in the summer of in the winter... the same settings have kept the alarms quiet.

I think you can become too OC about tire pressures. You want them right for the load. They are going to increase 15-25 psi just heading down the road at highway speeds. Your pressures and your monitor should account for that.

Gary

mbaril · 07-08-2019, 09:29 AM

I will change my steer tires from Good Year to Michelin this week. I was told at Spartan after being weighted to run 115 psi. Should I use the same PSI on Michelin?

Gary.Jones · 07-08-2019, 04:29 PM

Google Michelin Truck Tire Pressure / Load table. You will find the 2019 version. it will give you the minimum pressures you can run with their tires. By and large, most of the manufacturers use virtually the same table, but it is easy to find the Michelin load/pressure tables and if you know your weights, then you are in business. Use your 4 corner loaded weights and the pressure/load tables to determine your values. You can run higher than the table tells you (as it tells you the minimum) but your "ride" gets worse as you go far above the table values.

Gary

Tireman9 · 07-08-2019, 04:47 PM

Quote:

Originally Posted by buck58

2018 Aspire: setting tire pressure this am, in Florida. Even at 7 AM the temperature is between 73 and 75, depending on which side of the coach you’re on, based on the weight of my coach I should have 120 in the front and it says 75 in the back but I’m putting 85... But with it being so warm is that still accurate?

I would see no problem to inflate to 85 if your scale weight indicated you need a minimum of 75psi.

Also just because it is 73 - 75 when setting the pressure I see no reason to be concerned.

Tireman9 · 07-08-2019, 04:54 PM

Quote:

Originally Posted by Gary.Jones

Well, in point of fact, ambient temperature DOES make a difference. It makes a very big difference in something like a car tire.... it makes a difference for our coach tires, but less relative difference on a 120# 365 tire than a car tire. The biggest change for car is the difference between summer and winter or Florida and Colorado in the winter. My car tires will change maybe 5 psi and will set off my tire pressure monitors advising me of low tire pressure if I dont add additional pressure to the car tires at the beginning of the winter or the first really cold snap. However, once the tire pressure is set for typical winter temps, then I dont touch them again until spring/summer or significant warm ups. And my strategy works very well with the TPMS because I dont get warning of either high or low tire pressure on normal changes or drives during the winter or during the summer.

The change is less evident on a truck/coach tire. I generally dont do a lot of traveling in snow or very cold Norther temperatures.... my strategy is to avoid the cold by going where it is less cold. However, I set my coach tire pressures based on my 4-corner weights and my typical loaded coach loads, and for all intents and purposes, dont worry too much about them after they are set except to watch the temperature in the morning before any travel (what they call the cold temperature) or while on the road. My Valor TPMS system is set for I believe a 20% rise and a 15% fall (maybe 12.5%) before triggering alarms and once I got the tires set to the proper level for my loads, I have not had to change them in the summer of in the winter... the same settings have kept the alarms quiet.

I think you can become too OC about tire pressures. You want them right for the load. They are going to increase 15-25 psi just heading down the road at highway speeds. Your pressures and your monitor should account for that.

Gary

Not sure if I understand what you are claiming about pressure change.

"Gas Law" works out to about 2% for each 10F change, no matter if you are starting with a 30 psi passenger tire or a 100 psi 22.5 tire.

Gary.Jones · 07-09-2019, 06:25 PM

Im just saying I have to change my tire pressures every year on my cars and trucks as their TPMS throw low pressure alarms when the temp drops from the 80s down to the 30s. I have never had to change my tire pressure in the coach when the same thing happens.

I assume that it has to do with differing alarm percent changes built into the systems. I know the change is the same. My pressure are enough above the 4 corner weights and loads that I dont worry about it as much. If it drops enough to be a problem, I would add it... maybe because I live in Louisiana, it rarely is a problem in the coach.

Gary