Can You Ace this Race?

If I can't find cardboard, bottle caps, wooden skewers, or a drinking straw, what can I substitute so I can still build the car?

Use a cereal-box panel or thin plastic from a takeout container for the car body, large jar lids or cut CD pieces for wheels, straight pencils or wooden chopsticks as axles, and a cut pen barrel or a tightly rolled paper tube in place of the drinking straw while keeping the balloon attached and taped as in the airtight seal step.

The car won't roll smoothly or keeps veering—what parts of the build should I check and how can I fix them?

Check that the axle holes you made near the front and back are straight and slightly larger than the axles, that each bottle cap center hole is centered (widen with the tip of scissors if needed), that wheels are pushed on about one centimeter from the ends, and that the straw is taped straight back to the car body so nothing rubs against the wheels as described in the instructions.

How can I adapt this activity for younger kids or make it more challenging for older kids?

For younger children have an adult pre-cut the car body and make the axle holes and use big jar lids for easy wheels while supervising scissors, and for older kids require precise measured distances, test different balloon sizes and straw lengths for performance, and record times as in the racing step.

What are some fun ways to personalize or improve my balloon-powered car after the basic version works?

Decorate the car body with markers and tape on a cardboard spoiler, try low-friction ideas like adding small beads as spacers on the axles or using smoother wheels, experiment with different-sized balloons and straw placements, and then race and share results on DIY.org as suggested.