Tire inflation pressure when "cold".

[sailsmith]

I am towing a Sundance 3270RES. I recently had two blowouts within 16 miles of each other on I45 South of Dallas. It was 96 degrees, I had inflated my tires (Towmax) at 80 psi when "warm" and may have been traveling about 72 mph. I have owned my trailer 18 months and the tires have approx. 4500 miles on them.

I suspect that the tires were previously run underinflated on one particular trip. Therefore, the reasons for the blowouts on anybody's list would be "all of the above".

As an aside to this conversation, I have Good Sam's Roadside assistance. The first blowout, they handled perfectly. The second, I ask them to send out 2 new tires and since this was Sunday, father's day, and was late in the afternoon, we agreed that they would be brought to me the next morning. I luckily had a place to park for the night. The Goodyear store to do the service was suppose to bring me Goodyear Marathon tires, but instead, brought out Triangle tires, for which they still charged $201 each + mounting of $128. The average price I have seen these tires advertised online is $86. I am currently having conversations with Good Sam's Roadside concerning this.

The serviceman who mounted the tires recommended all my tires be inflated to 70 lbs. not the 80 lbs maximum. Sitting in my position at the time, that is what we did.

Now, HERE IS MY QUESTION.

Sitting in Houston, TX, with the outside temperature 97 degrees and the undriven tire temperature of 93 degrees per the TST 507 (new acquisition), How many psi should I inflate the tires?

They are currently showing 73-75 psi.

Thank you.

 

[danemayer]

Set the inflation in the morning when it's 75 degrees and no direct sun. Set them to the max cold pressure as stamped in the sidewall - probably 80 psi.

Don't tow faster than 65 mph. Almost all trailer tires are rated for a max speed of 65 mph. That's the max speed at which they can shed the heat that builds up. At 70 or 75 they'll overheat causing internal damage.

 

[EPaulikonis]

General rule of thumb is to add 1 psi for every 10 degrees of temperature. The start point is always 75 degrees as Dan mentioned. If you're max pressure on the sidewall is 80 psi and temperature is 97, you should be running 82 psi on a cold tire starting out.

Dan also makes a great point on speed. It is a major factor in tire failure often ignored by owners. Slow it down to 65 to protect your investment, and more importantly, the occupants of the TV. Towing safely is all about understanding the weights and restrictions to continue operating within the engineered envelope for both the TV and RV.

 

[alwayslooking]

Some RV manufactures and many auto manufactures are now filling their new vehicles' tires with nitrogen. Nitrogen has the advantage of not heating up and not losing pressure. It's major disadvantage is finding a source to refill your tires. I would agree that pulling a heavy trailer at 70+ mph in 95+ degree heat with under inflated tires rated at 65 mph is asking for trouble.

 

[justafordguy]

Your biggest problem was the fact that you had TowMax tires. They are junk and will blowout under perfect conditions. Get real tires, inflate them to max PSI marked on the tire, get a TPMS, stay at 65mph and have fun RVing.

 

[Garypowell]

Wait a minute....I thought we always start at 70 degrees and figure from there? I am on my iPad so can't do a lot of searching and writing.

About the second blowout. You have to remember that plus the previous damage you just damaged that second tire with the blow out of the first.

 

[Gaffer]

I thought it was 70 degrees as well.

 

[danemayer]

I thought it was 70 degrees as well.

The standard is 70. I picked 75 because this time of year in south Texas, morning temps are likely to be closer to 75.

Tireman9 has expressed the opinion that whatever the ambient temperature is, just inflate the tires to max cold pressure and don't worry about the 1 or 2 psi difference. My own non-expert opinion is that it's better to do the inflating in the morning at 75 than in the afternoon at 97.

 

[alwayslooking]

Also, technically your inflation pressure should match the load you're putting on the tires. If you are carrying a light load, you shouldn't have to inflate the tires to max. If the trailer is over the tire load limit, no amount of additional pressure will prevent problems. The manufacturer should provide a table to relate pressure to load. However, the safe thing to do is keep the inflation at or near the maximum rated pressure. Also remember that tires leak pressure. So, you should check and fill them regularly.

 

[Sniper]

Set air pressure to it's max load as stated on the sidewall (cold). TOWMAX as with most "trailer service only" tires are speed rated at 65 MPH.

 

[JohnD]

If the trailer is over the tire load limit, no amount of additional pressure will prevent problems.

I'm kind'a think'in that if the trailer is over the load limit of the tires, then maybe those tires shouldn't be on that trailer!

Just think'in out loud . . .