It's probably cos your so fat.
Joke.
Nah thats shit, you shouldnt expect that from any tube what so ever, unless its a tube of smarties or something. Try a moped tube, theyre thick as f**k. Or cut along the middle of a tube, and cut the valve out, so its like an extra protector thingy, kikda like this...
((()))
The black is the tyre, the blue is the old tube, cut along the middle, then the red is the original tube.
I dunno. Maybe lose weight?