About This Tool
This is a real-time online calculator to simulate bicycle gear ratio, skid patches, cadence (RPM), and speed relations. Select front chainring and rear cog teeth to instantly visualize detailed calculations.
Key Features
- Gear Ratio Calculation: Quantifies pedaling resistance to understand your ride characteristics.
- Skid Patch Calculation: Visualizes tire wear points for fixed gear (track/pist) bikes.
- Speed Simulator: Calculates your speed in km/h based on target cadence (RPM).
- Dynamic Animation: Features a bicycle animation that speeds up or slows down depending on your cadence and gear ratio.
Useful for customizing, maintaining, and setting up road bikes, minivelos, fixed gear bikes, and mountain bikes.
๐ Guide & Explanations
1. Select Mode
Choose "Single Speed" or "Multi (Derailleur)" in the mode tab.
- Single: Set teeth count directly. Ideal for single speed, BMX, or fixed gear skid patch calculations.
- Multi: Designed for road bikes or gravel bikes with front/rear derailleurs. You can simulate shifts in real-time.
๐ก Explanation: Single vs Multi vs Fixed Gear
๐ด Single Speed
Bicycles without a derailleur, featuring only one front chainring and one rear cog. Often seen on BMX and city cruisers. Lightweight and low maintenance, though climbing hills or battling wind is more difficult.
๐ต Multi Speed
Standard for road, gravel, and mountain bikes. Allows changing gears depending on terrain (lighter for climbs, heavier for descents or flats) to reduce fatigue over long distances.
โ๏ธ Fixed Gear (Pist)
Track racing style where the rear cog is locked to the hub. The pedals turn whenever the rear wheel is spinning, providing a direct connection to the road. (Please ensure front and rear brakes are installed for public road riding.)
2. Configure Gears
In "Multi" mode, choose standard presets (Shimano, SRAM, Campagnolo) or click "Manual โ" to input custom teeth configurations.
๐ก Explanation: Basics of Gear Ratio
What is Gear Ratio?
The gear ratio represents "how many times the rear wheel rotates for every single full rotation of the pedals."
For example, if Front is 48T and Rear is 16T, the gear ratio is 3.00. This means one turn of the pedals spins the rear wheel 3 times.
High vs Low Gear Ratio
- High Gear Ratio (Heavy): Faster top speeds but requires more leg power. Best for flat roads, downhills, or sprinting.
- Low Gear Ratio (Light): Lower top speed but very light pedaling. Crucial for steep climbs or starting from a stop.
3. Speed & Distance Simulation
Use the slider to change cadence (pedal RPM) and select your tire size. The tool will calculate the speed (km/h) and distance traveled per pedal stroke in real-time.
๐ก Explanation: Math Behind Speed & Distance
Distance per Pedal Rotation
Speed Calculation
- Cadence: Revolutions per minute (RPM)
- 60: Converts minutes to hours
- 1000: Converts meters to kilometers
4. Skid Patch (Single Speed Only)
Turning on "Calculate Skid Patches" displays the number of tire wear points for fixed gear track riders.
๐ก Explanation: What is a Skid Patch?
Calculates the number of points on the tire that rub against the road when you lock your legs (skidding) on a fixed gear bicycle. More patches distribute wear evenly, making tires last longer. The formula uses the greatest common divisor (GCD) of Front (F) and Rear (R) teeth:
*If you skid with either foot forward, the number of patches may double depending on the teeth combination (represented in parentheses).