Sailun S637 in 16" and 17.5" were being used by the regional service industry on trucks and trailers in the 2009 era.
The 16" S637 load G first came out as a LT for trucks and trailers like the 17.5" S637 are now.
I bought six LT S637 load G in 2010 for a GN triaxle trailer. Due to high tariff on imported LT tires Sailun changed lettering to the ST tire to get around those high fees sometimes in the 2010-2011 era (lower costs to the consumer). There now a ST although no changes were made according to Sailun reps/dealers.
Lots of new folks to the trailer towing world so naturally most know little about ST/P/LT tires on trailers or issues/non issues with brands of tires we use on trailers over the years.