These ST tires have a maximum load of about 15% more then an 235/85R16 LT tire, I searched for once and calculated for 80 psi pressure needed for the maximum load.
This is because of the more deflection they suppose to are allowed wich gives more surface on the ground so more load to carry with same pressure.
Thats the Theory, but in practice its better to give them the same deflection as a LT tire would have . This can be done with higher pressure , but you think the 80psi to be the maximum of the tire, like it is also for a standardload personscar tire.
But they print the maximum pressure ( further Pmax) on a Standload and also on a XL/Extraload/reinforced-tire ( different names for same kind of tire) and this is not the pressure they need for the maximum load up to 99m/h and no camber-angle. Normal car tire this pressure called the reference-pressure (further Pr) is 35psi for American tires and for XL// 41 psi . Difference between Pr and Pmax is used for higher speed and camber-angle above 2.
From C-load tires ( yours are 80 psi so E-load) they print something like this on the sidewall of the tire "maximum load xxxx lbs AT yyy psi(cold).
Then this yyy is the Pr and not the Pmax. So its allowed to go over that.
Found European article of Semperit( continental) in wich when standing still , the tire is allowed to carry 2 times the maximum load AT 1.4 times the Pr, so concluded that Pmax = 1.4 X Pr.
Even found an American article in wich is sayd that American TRA allows 10 psi above Pr for more load for LT tire, and better riding quality. For truck tires its even 20 psi. And for verry low speed even more load to carry then Pmax. here the article of goodyear with at botom page 1 and page 2 about that extra allowed. For ST I also found this 10psi higher but cant find it anymore , and it is for higher then 65m/h up to 75m/h and beter riding quality.
http://www.goodyear.com/truck/pdf/edb_loads.pdf
What can you do with this information.
If your valves can stand it, you can put 90psi in the same kind of tire when they are new , and probably this is enaugh to give the tire less deflection , so the treath wont come loose from it by to much bending of the sidewall. Because this is what happened at your tire.
together with some loadshifting to lighten up the side of the damaged tire, is probably also needed.
You can calculate a save pressure with my Traveltrailer-tirepressurecalculator, to be found in next map on my public map of skydrive wich belongs to my hotmail adress with same username as here.
https://skydrive.live.com/?cid=a526e...E092E6DC%21348
To use a spreadsheet first download it by
RIGHTCLICKING on it, then choose download from the dropdownbox. Not use the top 2 things or leftclick , first cant handle things I used in my spreadsheets, and second asks you to log in with your hotmail adres and password.
After download and eventual viruscheck ( you never know what those Dutch put in to it) it is opened in Excell or Open office CALC if you leftclick on the downloaded document.
Or you give the details , and I will do it for you with a picture of the filled in spreadsheet in my anwering post.
Best always is to weigh per side beter even, but in absence of that we have to do with the GVWR ( gross vehicle weight rating).
Hope this information helps you at your decicion for the new tires