The Rush SR tech regs allow two front sprocket options: 14-tooth and 15-tooth. Rear is locked at 44T. That’s it. No gear ratio spreadsheet rabbit holes.

15T is the factory default. Higher top speed, and the right answer at tracks with long straights — Road Atlanta, Watkins Glen. If you’re not sure, run 15T.

14T drops the gearing by about 7%. Tighter ratios, more acceleration out of slow corners. It’s the move at tight, technical circuits — CMP, Lime Rock, Laguna Seca. The tradeoff: you’ll hit the rev limiter in 6th on longer straights.

The table shows your theoretical speed at redline in each gear. In practice, you shift before redline — most fast drivers short-shift in lower gears and let it pull to redline in the higher ones. Aero drag also matters above 100 mph. These numbers are a planning tool, not a speedometer.

The track recommendations are based on what the fast guys run at each circuit. If you’re a rookie, run 15T everywhere until you know the tracks well enough to have an opinion. The sprocket swap takes 15 minutes.

Speed = RPM ÷ (primary ratio × gear ratio × final drive) × tire circumference. Primary reduction ratio is 1.5353:1. Tire is a Nankang AR-1 205/60R13 with 69″ loaded rolling circumference. All data from the official RUSH SR Gear Calculator.

Sprockets, chain, and tires are all available at raw-parts.com.