What SIZE tires do you have on your Class C??
A larger size in any brand of any given load range will be rated for more weight than the next size down. The stock size on most E450 Class C motorhomes can be changed out for the next size up and you gain enough higher weight carrying capacity to solve - or definitely help solve - your tire reliability problem.
Most owners - and tire shops - do not consider this when replacing tires on a Class C motorhome ... they just go with the "stock" size.
That being said, there is no substitute for high quality in Class C tires regardless of the size and load range considerations. Don't skip on tires to save money ... get the best you can possibly squeek out the money for ... even if you have to charge them and pay for them over time.
