KA gearing at 103rd street (kart + driver = 363 lbs):
I was hoping to fix the RaceStudio glitch I described in this thread (RaceStudio 3 tries to install on invalid drive) so I could get solid data, but I can’t, so I’ll just go with top speeds, laptimes, and seat of pants feel.
I tried 10:68 and 10:66. Not a huge difference between them. Both resulted in 67.9 to 68.9 mph top speed at the end of the straight on the “clockwise with chicane” track configuration and laptimes from high 38s to low 40s depending on new vs. cooked tires. Max rpm was mid 14ks. This held true in both hot day and cool night sessions. I cant say for sure which rear sprocket is faster without RaceStudio analysis of that sector to see which gains/loses time.
I think these ratios are close to ideal for this track configuration. The key is that it didn’t bog coming out of the slow hairpin before the front straight past the pits. I wouldn’t want to go too much lower on the gear ratio unless I was running without the chicane. With chicane, the extra top speed might not be worth it. That hairpin (slowest corner on track) is really slow. Important to keep revs up there.