Something I immediately noticed is that the s637 stand up straighter when on the ground, maybe its because of the higher pressure but I can see the sidewalls dont have nearly as much curve in them when rolling down the highway.
That rounded shape has always been one of the poor design features of the older ST tires.
Carlisle and Goodyear Marathon both have noted this as a softer ride in their previous website adds.
The ST G load range tires on the market seem to have lost that rounded sidewall profile and now look more like the flat sidewall profile tire on a semi trailer. Next time you get behind a semi trailer notice their flatter sidewall profile.
I wouldn't derate any load G tire to 80-85 psi. I have no idea how much you have over tired the trailer so;
This from rvsafety.com
Tire Load and Inflation Ratings
Note: Towable – Travel Trailer/ 5th Wheel owners Due to the severe use conditions experienced by tires when axles are very close together – tire industry experts recommend maximum (sidewall) inflation pressure for towable tires unless this causes a sever over-inflation situation (20psi+), often referred to as the ‘basketball effect’. If this is your situation allow a 10 – 15psi safety margin above the minimum required inflation pressure."
Those minimum pressure numbers on a tire load chart work well with a truck but a tire on a trailer has much more side loading stresses while the tire slides sideways around corners or backing maneuvers. Plus many trailers may have higher tire loads on one side vs the other. Experienced trailer owners know the benefit of max sidewall pressures or info from rvsafety.com above for your trailer needs.
