Give Grand Design Customer Service a call and ask them. That would be going straight to the source and they're a great bunch of folks up in Indiana (574-825-9679). Industry wide, though, blowouts are a tough situation. It's hard to prove the load, inflation, and lack of road hazards or debris.
You might also want to join the Grand Design Owners Forum. It's a very active group (not run by GD but they do monitor the "Technical Corner" sub-forum). Lots of folks with good experience over there:
Grand Design Owners ForumThe WestLake tires GD uses are "Super STs," load range "E" on the fifth wheels and rated for 75 MPH. Not a bad tire, really.
Rob
U.S. Army retired
2020 Solitude 310GK-R
MORryde IS, disc brakes, solar, DP windows
(Previously in a Reflection 337RLS)
2012 F350 CC DRW Lariat 6.7
Full-time since 8/2015