I have a InStep Sierra Double Bicycle Trailer that uses 16" tires, and I have gone through 3 inner tubes in the past week, they keep popping randomly. It's never when I'm using the trailer, just when it is sitting. At first I thought it was too much air pressure and sitting in the heat caused the air to expand and pop. But then I started pumping it up with less pressure and it just pops while stationary. It says no more than 35psi and I'm not going higher than that but it will pop an hour or two after pumping it up. Any ideas what would cause the tire to pop randomly? I can't find any debris in the rim. Should I use less pressure? Thanks in advance!