I'd like to tag onto this thread. My problem is tires failing during trips, damaging the camper.
My plan is to mount ST205/75R14 to measure clearance and switch. I want to get away from an impossible to find ST185/80D13 and extremely difficult to find ST185/80R13 that is under strength.
2008 Jayco 17c Ex-port Hybrid Travel Trailer, 3,500 Gross Weight. Each time weighed it is 3,450 - 3,500 Gross Weight. Bought HTT used Sep 2009, 7 week trip in June, July 2010. I use a Milton tire gauge rated tops and gauge up about each three days on the road.
In July, 2010, OEM Duro ST185/80D13 rated 1,660 Lbs at 65 psi. One tire blew out sidewall at 2,500 miles. Searched for replacement tire. No replacement in stock with those specs to be found in CO, NM, UT, AZ.
Replaced on the road with Maxxis ST185/80R13 rated 1,480 lb's at 50 psi, set of three, the strongest tire available, AND THE ONLY TIRE AVAILABLE, in 13's. To get those three we found one in Silida, CO and 2 in Moab UT. Called every town.
Oct, 2013, two Maxxis failed, at 14,000 miles, tread separation. One replaced with another brand (whatever available, the only ST185/80R13 within 100 miles of Memphis, TN). We caught one Maxxis inspecting tires one morning and changed it while cold in the campsite. Pressure 50 lbs, where it should be.
I can't stay with ST185/80R13 because of difficulty finding a replacement tire on the road and damage caused by failure. I do not have an option to use ST185/80D13 because they can't be found in stock anywhere.
So:
(1) try ST205/75R14 What weight do they carry? Range is D. They are easy to find.
or
(2) continue with ST185/80R13 carrying three spares and change at first sign of belt pealing off.