UNIVERSAL GEAR CALCULATOR Have a Porsche? Click here to try our Porsche specific calulator. Questions? Read our User & Collaboration Guide, call us at 510-907-9700 or email us. Ready to buy gears? Shop Now Use this form to email a customized PDF gearchart to yourself, your team, or to us at sales@retro-sport.com * Send to email: * Name: * Year / model: Phone #: Bottom: Peak Torque Line RPM Mid: Shift Point Line RPM Top: Red Line Max RPM Tire Diameter (in) Calculated tire circumference from diameter (in inches) Trans type #: Input Output Ratio Shift Point MPH RedLine Shift MPH Shift Point RPM Drop Red Line Shift RPM Drop Ring & Pinion Optional Tire Size Calculator Enter the width, aspect ratio, & rim diameter, then make sure to copy and paste the calculated diameter into the "Tire Diameter" field above. Width (mm) Aspect Ratio Rim Diameter (in) Diameter Circumference