Tires for the Cougar

According to the brochure goducks10 posted, your rig was placarded for =C= tires. If you've got D tires on it, you're actually above the factory recommendation. Personally, I see no reason to go any heavier than a D, though an E would be the next step. As donn said, the Goodyear Endurance seems to be doing quite well, though I've had good luck with the late model Carlisle tires and have no problems in recommending them. They're also cheaper than the Endurance. The old go-to tire, Maxxis, is being left in the dust by these newer tires, which are not only enjoying a better rep, but are speed rated to at least 10 mph over the Maxxis, which are still stuck at 65 mph. While I don't tow > 65, I figure that this means there's more safety margin while towing at my usual 62-63 mph tow speed; less heat build-up.

Lyle

Maxxis M8008 ST tires are a proven quality tire. They offer a 10 ply rated
Load Range E tire. Be sure they are balanced and you should consider metal valve stems.

go to a dealer who will sell you the next size bigger and load range G they will handle to load better. I used to have a blow out every time I went camping. went to tire store I shop at and told Gary this is bad, lets do something in the line of over kill. I never had another blow out

Thats the size that came on it in 2004.
https://www.keystonerv.com/media/1042319/2004.cougar.western.brochure.pdf.pdf

Correct tire size will be listed on the metal looking tag which is located on the street side near the front of the trailer. GoodYear Endurance ST tires are made in America and seem to have a good reputation based on the comments posted here and other forums.