Understanding Gear Ratios & Vehicle Speed
Gear ratios determine the mechanical advantage of your engine's power. By calculating the overall reduction (Gear Ratio × Final Drive), we can determine exactly how fast the wheels turn for every revolution of the crankshaft.
Tire Diameter Calculation
Your tire size (e.g., 225/45R17) directly impacts speed. The width (225mm) and aspect ratio (45%) determine the sidewall height. Doubling this and adding the wheel diameter (17 inches) gives the total rolling diameter. A larger tire will effectively 'lengthen' your gears, resulting in a higher top speed but slower acceleration.
Optimizing for Performance
For racing or track use, gear ratios are chosen to keep the engine in its 'power band' after every shift. By visualizing the speed curve, you can see how much RPM will drop when shifting from one gear to the next. Ideally, you want the RPM to fall back to the engine's peak torque point.