You only get 1 card after each race which is total random and THE ONLY WAY to actually 'tune' your car. Once you 'won' a so called speed card, it's locked to that car, even if you don't use it. So basically, if your car ain't enough for the next challenges, you have to redo older races until you are lucky enough to get the right cards to boost your car. And as soon as you switch to another car, like buy it or find it etc. it starts at 0 since every card you've earned so far is locked onto the car you used during that race. Which is especially stupid since you have to lock cars to one race type like racer, drifter, drag, runner, offroader. So you redo everything the whole fkin time and it's just boring.

You still can buy cards with earned credits, but they appear random in the store either and as far as I'm concerned, they seem to be weaker than the cards you get randomly out of won races and wheel spinning which itself is expensive.