Mousetrap Vehicle

We started our mousetrap vehicle about two weeks ago. For our vehicle we used two records for the back wheels, two CD's for the front wheels, light wood for the chassis, wooden dowels for the axels, pipe holders to attach the axel to the chassis and hot glue to attach everything together.
At first we used fish line as the string, but that was too small and it wouldn't stay wound and it would only go about two meters. We then decided to use normal white string. After we switched the string, our vehicle started to go about five meters but it turns to the left because the wheels are very straight.

Our mousetrap vehicle