I had load range D tires on my trailer that require 65 psi. They are the right load range for the trailer, but I wanted 10 ply so when it was time to change the tires I changed to load range E which is 80 psi.The place I bought the tires from filled them to 65 psi (didn't notice until a few weeks later) but everything I am reading says always fill ST tires to the max. So should I fill the tires based on trailer weight or the tire?

I had a similar experience when I got new Carlisle's last year. They were at 65, but the side wall said max @ 80. I towed it that way a while and after a few suggestions on these forums, this spring decided to go ahead and push it to 80 psi. So far, ... um ... I really can't tell any difference.

Just a thought , maybe the tire shop only put in 65# because the wheel is only rated for 65#. I don't know if the OEM wheel will handle 80# safely. ( ? )

I did the same thing on mine. Very glad I did. Mine has aluminum rims and there were no ratings for weight or pressure. The dealer I bought them from said being aluminum they should handle the increased pressure. I am now on my second set of 10 ply tires and no problems at 80psi.

Run them at 80psi cold inflation.

Did you get high pressure stems? Otherwise yes I would run them 75/80 psi.

Upgraded tires - air pressure? | Good Sam Community

24 Replies

wrgrs50s
Explorer
May 19, 2017
I was told by my wheel manufacturer that if you have 5 lug rims the recommended pressure is 65psi and that 6 lugs are good for 80psi.

I have 6 lugs and upgraded to E tires and run 80psi for the last 5 yrs, with no problems. It dont make sense to me to upgrade to an e tire and not take advantage of the additional load capacity. Running a tire below it's recommendd inflation is more likely to cause heat related failures.

I know there's charts out there by tire manufacturers that state that a tire only needs to be inflated to a point that matches it's load requirement but "hey" they get to sell you a new tire if it fails. I've yet to see any data that says a tire has been known to fail if inflated to the tire manufacturers suggested pressure stamped on the tire.
Lwiddis
Explorer II
May 19, 2017
Ksg, I know of no recommendation that TT tires not be inflated cold to max sidewall pressure. In my case LR D is 65 psi. And Lady agrees...she must be running LR Es.
LadyRVer
Explorer II
May 19, 2017
When the tire shop upgraded the load range for my new tires, they aired the new tires from 65psi to 80psi as stated on the new tire. I have towed with the 80psi for 18 mo . now.
Huntindog
Explorer
May 19, 2017
One thing to consider, especially for ST tires which generally have a bad reputation for reliability... In the case of a blowout, If you only have 65 psi in the tires, the remaining tire will most likely be severely overloaded.
To the point that it should be considered damaged and replaced along with the blowout.
If 80 psi is used, the overload (if any) will be a lot less. In my case, I would take it out of service, but use it for a spare.

Blowouts on TTs are problematic. Often they go unnoticed for many miles. The TT usually doesn't tow much different. So lots of damage can be done. Both to a remaining overloaded tire, and to the TT from the steel belts whipping around acting like a chainsaw on the TT.

This why I use Michelin XPS RIBS. Very expensive, and VERY reliable.
ksg5000
Explorer
May 19, 2017
I don't know about trailers but in an RV/motorhome you fill the tire based on the weight of the rig. Further - I upgraded from D's to E's on my Class C - the wheel/rim of the rig has stamp indicating it's designed for lower pressure of D tire - using higher pressure might create an issue.
Lwiddis
Explorer II
May 18, 2017
"So should I fill the tires based on trailer weight or the tire?"

Fill to manufacturer specs. If you don't and have an issue...you lose...intentionally disregarded manufacturer's specs. That's one reason I stay with LR Ds...65 psi.
LoudDog
Explorer
May 18, 2017
time2roll wrote:
Did you get high pressure stems? Otherwise yes I would run them 75/80 psi.

Would there be different stems for 65 or 80 psi?
LoudDog
Explorer
May 18, 2017
Thanks! I had bumped them up to 80 when I caught it, but was second guessing myself.
Sam_Spade
Explorer
May 18, 2017
downtheroad wrote:
Run them at 80psi cold inflation.

Why ? What perceived gain is there in doing that ??

The required pressure is determined mostly by the weight carried.
Stepping up one load range should NOT require more pressure to carry the load properly.

THE NUMBER ON THE SIDEWALL INDICATING THE MAXIMUM SAFE PRESSURE HAS ****NOTHING**** TO DO WITH THE PROPER PRESSURE.
time2roll
Nomad
May 18, 2017
Did you get high pressure stems? Otherwise yes I would run them 75/80 psi.

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Upgraded tires - air pressure?

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