We just decided to change our idea.. well a BIT, we discovered that our balloon car was a BIT TOO heavy, so... here are the changes :
1. took out one wheel, to make the ballon car have THREE wheels.
2. you know that red part you see in the picture of our recent ballooncar ? The one that is attaching the wheels to the car? We changed those knex parts to bbq sticks ! AND OBVIOUSLY it reduced the weight of the car by a lot :)