I used to do quite a few race cars every spring but, after a few years , it became obvious where it was all heading. The car owners might be willing to pay the first year but, most of them asked us to donate our time and materials in exchange for ad space on the cars. That may seem like a great deal until you realize that advertising on race cars will only bring you more work on race cars owned by people who want you to sponsor them for free. That's not to say that you will never get any other types of paying work from the racing industry or fans but, for the most part - it was a losing proposition for us. The race car guys were some of the toughest customers to get paid from, I've known some of them to just go from one sign shop to the next without ever paying a penny.
I donate work to some local charities and am glad to do so but, I don't consider auto racing to be a "Charitable Organization".
Another consideration is that prints can be more susceptible to abrasion damage than solid opaque vinyl. The laminate and ink will get rubbed off in places leaving the white media or substrate color showing through making things rather ugly and illegible very quickly.
