Another post with a question on an RV Forum.
I've often wondered why the tires on my travel trailer will gain about 10-12psi on a trip, and the tires on my tow truck only gain about 4-5 psi. The tires on my trailer are Goodyear Endurance load range E, with a cold pressure rating of 80psi. (The original Chinese tire bombs were load range D with a cold pressure rating of 65psi. I had the same problem with them gaining pressure). I usually start my trips with the pressure set at 75psi instead of 80psi because I'm nervous about the tires gaining so much pressure. On a typical travel day in the summer (in Texas) the tires will usually go from 75 to about 87 or 88psi cruising down the highway at 65MPH. I have a pressure monitoring system, and I have a lot of faith in it. My trailer weighs 9950lbs according the the CAT scale.
Tire pressure will increase i.e. gain about 2% for each increase in temperature of 10F. I have covered this in detail in a few posts on my blog. Here is one post on that topic.
Since your TT tires carry a much higher load relative to the tire
size they have to work harder than your truck tires. Inflation on
trucks gives tires a 10% to 30% Reserve load while the inflation
specified for TT tries may give 0% Reserve and the sad fact is that based on actual tire loading data a MAJORITY or RV trailers actually have a negative reserve (i.e. they are overloaded).
What can confuse the issue is when you change the Load Range you can run a different pressure BUT a couple observations. When you increase the tire Load Range you only get an increase in load Capacity when you also run higher inflation.
Without knowing the scale reading for each axle and the actual tire sizes I can only give you generalizations. It is very unlikely that your 9950# is evenly split across all 4 tires and probably one or more is supporting more than 2,487#.
You should NOT get nervous about pressure gain as we tire engineers know the temperature will increase and also the pressure will increase. You can email me directly at firstname.lastname@example.org and I will be happy to work directly with you to resolve your questions and concerns.
Some information that will help us.
1. Complete tire size and Load Range info for both TT and TV
2. Scale readings for all 4 axles (TV & TT)
3. Cold inflation for the TV. You said 75 for the 4 TT tires
Well I posted the above a couple weeks ago but have not heard back so either the OP has lost interest, or doesn't want to discuss the problem.
If you are reading this blog post then you probably care about your tire inflation and understand the normal pressure increase. If not my offer to help still stands, but please provide the requested information so we both don't spend time going back and forth.