Community Forums

LandKO · 09-20-2016, 08:00 PM

My TT is 26 ft long, dual axle, w/ Trailer King ST205/75R14 tires. Trailer GVWR is 6000 lbs. Recommended tire pressure is 50psi cold.

I sometimes see an easy 5 psi increase in tire pressure (on my TPMS) on a hot day so I have been running the cold tire pressure about 46-47 psi. I don't think this will cause any tire damage but my main concern is over inflation at highway speeds.

My question is, if I check the "cold" tire pressure when the ambient air temperature is in the high 80's low 90's and then travel on a day where the air temperature is near 100 degrees f, what should I be setting the high pressure alarm point on my TPMS?

Thanks for any input.

Mich F · 09-20-2016, 08:56 PM

Your tires are probably 1,760# load rated at 50# psi. I'd suggest you set your tires to 50# . The manufacturers know they will heat up while driving. I'd be more concerned with your under inflation.

1bigmess · 09-20-2016, 09:00 PM

Quote:

Originally Posted by Mich F

Your tires are probably 1,760# load rated at 50# psi. I'd suggest you set your tires to 50# . The manufacturers know they will heat up while driving.

Hearty +1. Don't play tire engineer unless you are one. There is really only one safest inflation pressure for ST tires, and that is max inflation, especially if it's a dual axle trailer.

Mr_D · 09-20-2016, 09:09 PM

Quote:

Originally Posted by 1bigmess

Hearty +1. Don't play tire engineer unless you are one. There is really only one safest inflation pressure for ST tires, and that is max inflation, especially if it's a dual axle trailer.

Yep, ST tires are to be run at their maximum cold pressure. Do NOT try and guess nor deflate the pressure given. The tires are designed to have higher pressure as the tire warms up. All tires are to be inflated ONLY when cold IE, sitting overnight and not driven more than 1 mile.

LandKO · 09-21-2016, 07:05 AM

Thanks for the input. Being new to RVing, it seemed strange to me to run a tire at such high pressures.
However, my original question didn't get answered. This was, what should I be using as a high pressure alarm point on my TPMS.
So, I did some internet research this morning. On the Trailer King website there is a page on maintenance.
On this page it addresses proper inflation. It verifies what has been said in the above posts, but it also says that when a tire is checked when HOT, it is OK to be over the max cold pressure by as much as 10 psi.
So I will set my TPMS over pressure alarm at this setting.
I provide below an excerpt from the webpage.

"PROPER INFLATION

When it comes to maintenance, keeping your RV tires inflated to the proper pressure is the most important thing you can do to insure their long life. Follow the guidelines in your RV owner's manual if you have one. If you don't have an owners manual then asked an expert, either a good tire man or your RV service tech.

The maximum pressure allowed for a tire is embossed on the side wall. That's the maximum pressure when the tire is cold. It's okay for it to be over that by as much as 10 psi if tire pressure is checked while hot. However, always check air pressure when tires are cold for accurate reading. The proper pressure for your RV tire may not be the maximum tire pressure. The right pressure is determined by the weight carried by each tire on the RV and the pressure recommend by the tire manufacture for that weight.

Running a tire in an over pressure condition will cause uneven tread wear. Running a tire in an under pressure condition will also cause uneven tread wear and can cause damage to the side walls of the tire. Keep in mind that a tire can lose as much a 1 psi per month and as little as 5 psi can make a difference in the load carrying capacity of a tire. So, it's especially important to check and adjust your tire pressure before taking your rig on that first trip of the season. Then check tire pressure once a month."

Mich F · 09-21-2016, 07:33 AM

You might be unaware that your trailer tires probably have a maximum speed rating of 65 MPH. Many people seem to be unaware or just don't care about that fact.

Some tires are rated higher than that, but many are limited to 65 MPH.

Gary RVRoamer · 09-21-2016, 02:59 PM

"Cold" means "not driven for several hours". It has nothing to do with ambient temperature, so never make an allowance for air temperature or for heat that builds up as you drive. You will be driving on under-inflated tires and they won't last long.

Always inflate the tires to the required pressure before driving for the day.

BrianGlenn · 09-21-2016, 04:38 PM

Quote:

Originally Posted by Gary RVRoamer

"Cold" means "not driven for several hours". It has nothing to do with ambient temperature, so never make an allowance for air temperature or for heat that builds up as you drive. You will be driving on under-inflated tires and they won't last long.

Always inflate the tires to the required pressure before driving for the day.

I agree. However there was that one exception for me - 110psi G rated Goodyear checked at 110 at Cedar City Utah, 32F that morning. Pulled into Vegas at 3:00PM 80F, TPMS alarm went off at 130 psi. Unique driving scenario, and not normally encountered.

OP. About 10 pounds over 50 psi cold is a good number for high TPMS set.

Brian.

monkey · 09-21-2016, 08:34 PM

Agree... Set your pressures to max when "cold",,, as in not driven for a few hours.... In our class A I used a pressure vs load chart,,, but now with this 5vr, even though I got rid of the "trailer king china bombs",,, My Maxxis tires are always within 3-4 PSI of max,, even though they are over rated for the load.... NO MORE than 65 mph on those tires!!! Less mph is better,......
Monkey

Tightwadted · 09-21-2016, 09:02 PM

LandKO, I agree with other posters, on those loadrange C tires put em at the 50 psi, you don't have much cushion, one thing you will find out with the TPMS is that strong side winds will affect temp and psi differences side to side as will one side running in the sun vs shade. On a side note, when you eventually get new tires upgrade to load range D if your rims will handle the 65 psi.

Gary RVRoamer · 09-22-2016, 11:12 AM

Quote:

I agree. However there was that one exception for me - 110psi G rated Goodyear checked at 110 at Cedar City Utah, 32F that morning. Pulled into Vegas at 3:00PM 80F, TPMS alarm went off at 130 psi. Unique driving scenario, and not normally encountered.

Sure, but you were still within the tire's psi capability, so no need to lower pressure in anticipation of the change. If, the next morning, you are still in warmer weather, the "cold" pressure you previously set at 32 F. will be somewhat higher (greater than what you set before) because the ambient is now higher and tire pressure naturally increases. At that point you may choose to re-adjust (lower) the cold pressure so it is still at the correct "cold" value for the load. What you don't do is let air out to below the recommended pressure, no matter how hot you think it may be later in the day. The tire engineers have already done that thinking for you, so stick with their recommended pressures.