Any suggestions? I've blown the front and bike tubes in a matter of two trips out. Lots of limestone rocks that are like knives. I've switched to the green slime tubes. The one up front survived the first trip out since the blow out, but that was when I blew the back. I'm hoping the slime takes care of it. There are also apparently solid rubber tubes with no air, but I was told they're not fun to ride on... any suggestions?