i have a friend who's very competetive. we both got our bikes at the same time from the same LBS. i knew that later that night, he'd want to weigh both our bikes to see who had the lightest bike.

so, before he came over- i took off my seat tube and dropped about 9 "C" cell batteries down my seat tube.

when he came over- we had a beer... bs'd for a half hour... and then he asked to use the scale as he was curious about the weight of his bike. one thing leads to another--

the funny thing is- he now knows he has this svelte 15.5 lbs bike... and he THINKS i've this 18+lbs POS...

so its TWICE as demoralizing when i out sprint him or beat him up a hill.


just an example of a safe prank where you mess with OWN stuff and it turns out to be more effective.