Nissan 240SX - Performance

Top Speed Calculator

This tool is useful for experimenting with various gear ratios and wheel/tire combinations. It can be used to find your overall top speed and your maximum speed for each gear of the transmission. Download this PDF File or Word File to see how the calculation is done. The default values entered in the calculator are for a stock 1990 240SX in fifth gear on 195/60R15 tires.

Redline (or other RPM to use):
Tire Width (mm) (Example: 195/60R15):
Aspect Ratio* (Example: 195/60R15):
Rim Diameter (in.) (Example: 195/60R15):
Transmission Gear Ratio (Example: 0.759:1):
Final Gear Ratio (Example: 4.083:1):

* The Aspect Ratio is the sidewall height divided by the tire width.

Another useful tool related to choosing a wheel/tire combination is this Tire Size Calculator from It will let you experiment with different tire sizes and see how they will affect your speedometer reading.