Here's an interesting question. Some friends and I were playing last night and used 14 damage markers on the track (amazingly no cars were eliminated due to collisions). Of the remaining 6 markers, 4 were used as "Soft Tire" indicators on dashboards and 2 unused. My question is this, how have other players/groups dealt with lack of damage counters?
We've honestly never run out. Don't think any of the rules actually mention component limitations, but I think it's pretty obvious you're just supposed to use some substitute should you run out. We almost never use the damage tokens anyway, as we've always used small squares cut from pink post-its instead. Much easier as they stick to the surface and can easily be peeled off after the race and re-used.
I printed out custom cards for the driver/cars that also have tire markers. My excel file is available in the files section of Formula D. I am trying to get some acrylic transparent damage markers that will allow players to see the corner markings on the board. I'll post some pictures when they are finished, as well as a link to where you can buy them.