Trailer and truck tire pressures?

[Blaise]

We are on a cross country trip from NY to CA, in KY at the moment. Before we left, I checked trailer tire pressures - all 4 tires were at about 65 PSI. The tag on the trailer says "cold pressure 80 PSI". So I pumped them up to 80 PSI each. Our GD Reflection has the "Compass Connect" feature - a phone app that connects to the trailer via blutooth. It allows you to control a bunch of stuff with your phone (lights on and off, slides in and out, leveling, etc). It also integrates the Tire Linc TPMS, which agreed with my pump that the tires were at 80 PSI. This was in NY with cold tires and an ambient temp of about 45 degrees F.

I knew temp and pressure would increase with driving, but I didn't know how much variance to expect. I set the pressure limits to 72 and 88 (+/- 8 PSI). We get on the road, and the TPMS squawks pretty quickly, complaining of PSI in the low 90's. Ambient temp was in the 80's. I let a bit of air out and increased the max limit to 95. TPMS warning went off again - pressures at 95 and tire temps in the 90's. It is quite a bit warmer here than it was in NY - ambient temp is low 80's. So the "cold" pressure of 80 here has got to be different than in NY. I mean, 80 PSI is 80 PSI. But if that is measured with an ambient temp of 45, the increase in pressure will be greater than if you set the tires at 80 PSI with an ambient temp of 75, no?

So what should I expect in terms of actual tire pressures and temps when "hot" (driving)? Trying to set reasonable tire pressure limits on the TPMS and stay safe.

The truck (a long bed dually) has a similar story, but less extreme: tires set to spec, front at 70 PSI and rear at 80 PSI (cold). Both are running about plus 10 PSI while driving.

Thanks for any guidance.

 

[Derby6]

OK. I’m no expert but tire pressures can increase significantly when the tires heat up. I see 10+ degree difference when one side in sun and other shaded as I go down the highway.
I don’t worry about pressure limits. Fill cold as you did and have alarm when they get low.

 

[CharlesinGA]

On my ST227/75R15 tires on my trailer I see a good 5 to 7 psi increase from cold temps (moderate ambient temp, possibly 60 or so) and sometimes more than that on the sunny side of the trailer. This is my cold readings from several days ago during a discussion on trip prepping. I have not serviced the tires since last fall, they don't leak at all, and the trailer is in a insulated metal building with some heat so I just leave them alone.

If your placard on the side of the trailer calls for 80, I'd set them to 80 when the temps are moderate and watch the pressures and set the limits high enough to not alert on you.

I am using the Lippert Connect ONLY for the tire pressures (the app they called for was Lippert One Control and I was never able to make that work, (apparently no one else could either based on the reviews and ratings) so I spotted Connect and after fighting with it, I was able to get it to work, and with the new Samsung phone it works better than the older Motorola I was using. I highly suggest getting the Alert Indicator and syncing it to the system. It will beep momentarily when you begin rolling to let you know it is receiving all tires and sometimes when you lose an indication you get an alert and when you look on the phone it will show a ! if it has not reconnected. I don't think I got that at all on this last trip of over 1200 miles. It has a rechargeable battery in it, and it searches for a signal from the repeater more often if it is plugged in, hence the cord you see in the pic. It will work without the cord however. I have it mounted with 3M Dual-Lock from Home Depot and when not towing I just put it on the dinette and plug it in to one of my USB cords (trailer is powered all the time in the shop).

Charles

 

[Ray-IN]

We are on a cross country trip from NY to CA, in KY at the moment. Before we left, I checked trailer tire pressures - all 4 tires were at about 65 PSI. The tag on the trailer says "cold pressure 80 PSI". So I pumped them up to 80 PSI each. Our GD Reflection has the "Compass Connect" feature - a phone app that connects to the trailer via blutooth. It allows you to control a bunch of stuff with your phone (lights on and off, slides in and out, leveling, etc). It also integrates the Tire Linc TPMS, which agreed with my pump that the tires were at 80 PSI. This was in NY with cold tires and an ambient temp of about 45 degrees F.

I knew temp and pressure would increase with driving, but I didn't know how much variance to expect. I set the pressure limits to 72 and 88 (+/- 8 PSI). We get on the road, and the TPMS squawks pretty quickly, complaining of PSI in the low 90's. Ambient temp was in the 80's. I let a bit of air out and increased the max limit to 95. TPMS warning went off again - pressures at 95 and tire temps in the 90's. It is quite a bit warmer here than it was in NY - ambient temp is low 80's. So the "cold" pressure of 80 here has got to be different than in NY. I mean, 80 PSI is 80 PSI. But if that is measured with an ambient temp of 45, the increase in pressure will be greater than if you set the tires at 80 PSI with an ambient temp of 75, no?

So what should I expect in terms of actual tire pressures and temps when "hot" (driving)? Trying to set reasonable tire pressure limits on the TPMS and stay safe.

The truck (a long bed dually) has a similar story, but less extreme: tires set to spec, front at 70 PSI and rear at 80 PSI (cold). Both are running about plus 10 PSI while driving.

Thanks for any guidance.

Sidewall flex produces the most heat in a tire. Running less than the Federal tire Placard stated pressures produces more heat, which results in a wider pressure differential between cold and hot.
You're over-thinking this IMO.
What did you do before TPMS were invented?

 

[Gary RV_Wizard]

Trying to guess how much pressure & temperature may increase is mostly futile and not at all necessary. Just set to the recommended 80 psi and turn the TPMS upper range up high enough to shut it up. Then observe the cold pressure each morning and adjust if needed to stay at 80 psi.

The temperature range may possibly give you advance warning of a sticking brake or bad wheel bearing. Those things can cause massive overheating even though the tire psi is fine. It is not useful for tire pressure monitoring, except maybe for a severely underinflated tire (and you already have the low psi warning for that).

 

[Blaise]

Thanks to all for the comments and guidance. I have set the TPMS upper limit to 99 PSI and get an occasional alert when connection to a sensor is temporarily lost.

Cold pressures with an ambient temp of 72 in Park City KY are to spec (around 80 PSI).

We'll be departing for MO in about an hour, and I can now do so without unnecessary concerns.

Thank you!

 

[Blaise]

On my ST227/75R15 tires on my trailer I see a good 5 to 7 psi increase from cold temps (moderate ambient temp, possibly 60 or so) and sometimes more than that on the sunny side of the trailer. This is my cold readings from several days ago during a discussion on trip prepping. I have not serviced the tires since last fall, they don't leak at all, and the trailer is in a insulated metal building with some heat so I just leave them alone.

If your placard on the side of the trailer calls for 80, I'd set them to 80 when the temps are moderate and watch the pressures and set the limits high enough to not alert on you.

I am using the Lippert Connect ONLY for the tire pressures (the app they called for was Lippert One Control and I was never able to make that work, (apparently no one else could either based on the reviews and ratings) so I spotted Connect and after fighting with it, I was able to get it to work, and with the new Samsung phone it works better than the older Motorola I was using. I highly suggest getting the Alert Indicator and syncing it to the system. It will beep momentarily when you begin rolling to let you know it is receiving all tires and sometimes when you lose an indication you get an alert and when you look on the phone it will show a ! if it has not reconnected. I don't think I got that at all on this last trip of over 1200 miles. It has a rechargeable battery in it, and it searches for a signal from the repeater more often if it is plugged in, hence the cord you see in the pic. It will work without the cord however. I have it mounted with 3M Dual-Lock from Home Depot and when not towing I just put it on the dinette and plug it in to one of my USB cords (trailer is powered all the time in the shop).

Charles

@CharlesinGA thanks for the pics. We are using the alert dohickey, which I like because I don't have to constantly be checking pressures in the connect app. When / if it alerts, I open the app and look. Very convenient!

 

[oldryder]

If you are traveling where the morning temps will vary significantly you might want one of the battery powered auto shut off tire inflators. You just set the pressure and walk away while you do other things to get going. I use a dewalt unit that is compact and seems to be accurate, matches my good tire gauge.