Med-large 120' asphalt straight, but technical track, we geared around a 4.8 FDR probably because of the tighter sections. That's a 43 pinion and 104 spur on the RDX. We have geared as high as 47 tooth and as low as 42 tooth. That was on 62 to 63mm rubber tires. It would be to 46 to 52 teeth for 57 mm tires. You would go down up to 20% for tight carpet tracks so that gives you a range.
Rollout = 3.14 x diam / FDR = 37.3 mm (4.84 FDR). High end 36.4 to 40.8mm for larger asphalt tracks. Low end ~29mm or so.