My 28 ft Vintage had 225x15 Goodyear Marathon's.
For the 4 years they were on it I only had 1
that bulged. I always kept them covered, at
70 psi and rotated them every spring.

I now have BFG Commercial A/S TA's in 225x16.
They only added 1/2in in height. I found a set
of 5 16in 5th wheel Alum wheels on craigslist
for $100. Best thing I did for the trailer, It
tows so much better. No wishy washy sway on the
ruts and bumps of the hi-way, course the hitch
must set up correctly.

I had 40ft 3 axle with 225x15 marathons before
and as long as I kept the pressure at 70, covered
and rotated, I never had had a blowout in 8
years. I did have 3 bulges tho.

Sorry this is long but I firmly believe that
checking the lugs & psi before every tow,
covering when not in use and rotating every
year is a must do.

Rick