Finds and credits
Finds sit next to obstacles, away from the trailhead and the garage. The same course number and difficulty always put them in the same places.
A find is a part, a tire and rim, or a bundle of credits. Credit bundles are bigger at harder obstacles. Parts go into your inventory. A tire-and-rim find adds one tire and one rim.
Parts come in Common, Uncommon and Rare. Common and Uncommon parts can also be bought in the shop. Rare parts only turn up as finds.
You earn credits while you drive. Spend them on shop parts and on more stock rig builds.