Underinflation and speed may contribute to blowouts but the real problem for many of us is bad, often Chinese made tires.
I tow boats 4 days a week for our watershow operation, on a road trip we may have as many as 8 trailers.
This will be my 40th year of doing so.
Example 1: One of our smaller single rigs (only one motor) still had the original tires on it after 15 years, deep cracks, worn out, General brand and still no failures. We purchased new tires from Tires Plus, Nanco brand, highly recommended by the seller. 3 of the 4 blew on the first road trip of about 300 miles. Yes fully inflated and towed on 2 lane roads at lower speeds. Tires Plus did not stand behind them, claiming the same as some writers on here. They talked our treasurer into buying 6 ply rated tires, same brand, 75 lb tires......same results, just a louder bang when they blow!
Remember the original Generals never gave trouble and were only 4 ply, 50 lb tires.
Example 2: A new triple rig we purchased, $80,000 invested, also a tandem axle. 7,000 lbs of capacity, actual weight of 5,000 lbs. Within 2 years all 4 had blown out. One blew about 1 mile from our hotel (road trip) after I had gotten up early, walked around carefully checking tire pressure, etc. Could still see the hotel from the interstate on ramp....blew completely apart throwing the entire center out. Radial Trail CRT was the brand on the sidewall, made in China.
The next 8 years - till now---have been on Goodyears and have had no failures.
I could give more examples...but here is my takeaway. We replace with Goodyear Marathons and have no further problems. Likely other major brands are good also. Car tires are always good on our boat trailers and we often use them when the capacity ratings are adequate. One of our twin rigs weighed 4,400 lbs and was towed for many years with car tires only rated to hold up 3400 lbs total and they ran until worn out.
Incidentally, I contacted DOT about the 100% failure rate brands and learned that they do not test trailer tires.....only car tires for the DOT certification. Many of you older car buffs may remember when they began testing car tires, lots of them blew out when tested at their rated capacity and tire quality was forced to greatly improve at that time. Hopefully the current deregulation trend will not return us to the 1950's and 60's when blowouts were a standard part of driving.
Titan, who makes large equipment tires and we thought had a good reputation bought a Firestone Factory, fired all the help and brought in replacement workers. Yeah we live nearby....got some of their tires, 100 percent failures, although they usually threw part of the tread off before blowing, you might get 5 miles of warning and find a safe place to pull over.
I could go on, but I know that none of our blowouts were the users fault!
fsskier