A fixed-gear skid patch calculator uses Greatest Common Divisor math to determine how many unique tire contact points your drivetrain geometry creates when skidding. Enter chainring and cog tooth counts to see patch count, gear ratio, gear inches, and development per pedal revolution.
Nearby Ratio Comparison
| Chainring | Cog | Ratio | Patches | Gear Inches | Rating |
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Track Drivetrain Upgrades
If you're shredding through tires because you ride a 48/16 ratio (which only gives you 1 single skid patch), the cheapest and most effective upgrade you can make is swapping your rear cog. We recommend upgrading to a CNC-machined 17T track cog. Switching to a prime number like 17 instantly maximizes your skid patches to 17 (or 34 if ambidextrous), drastically increasing the lifespan of your tires. To ensure maximum power transfer and prevent chain slip during heavy braking, pair it with a dedicated KMC K1SL single-speed track chain.
How to Calculate Fixed Gear Skid Patches
On a fixed-gear bicycle, the rear wheel is directly tied to the rotation of the crank arms; you cannot coast. When a rider locks their legs to stop the rotation of the pedals (skidding), the rear tire halts and drags across the pavement. Because the chainring and rear cog are mechanically linked, the pedals will only lock in a specific, repeatable number of positions relative to the rear wheel. The number of these unique stopping points on the tire is known as "skid patches." To calculate this manually, you simplify the fraction of (Chainring Teeth / Cog Teeth). The denominator of that simplified fraction is your number of skid patches. For example, 48/16 simplifies to 3/1, meaning you only get 1 skid patch, and your tire will wear out in exactly one spot very quickly. 49/17 cannot be simplified, giving you 17 distinct skid patches and perfectly even tire wear. SkidPatch instantly calculates this geometry for you, alongside Gear Inches (how hard the bike is to pedal) and Development (how far the bike travels per pedal stroke).
Frequently Asked Questions
What are skid patches on a fixed gear bike?
Skid patches are the points on your rear tire that contact the ground when you lock the drivetrain and skid. The number of patches depends on your gear ratio's Greatest Common Divisor (GCD). Fewer patches mean those spots wear faster, shortening tire life. More patches distribute wear more evenly.
How do you calculate skid patches?
Skid patches = Rear Cog Teeth / GCD(Chainring, Cog). For a 46/16 setup: GCD(46,16) = 2, so patches = 16/2 = 8. If you skid with both feet (ambidextrous skidding), double the count: 8 × 2 = 16 patches. Prime number cog teeth (17, 19) maximize patch count because they share no common factors with most chainrings.
What gear ratio is best for fixed gear riding?
Most urban fixed gear riders use ratios between 2.5:1 and 2.9:1. A 46/17 (2.71:1) is the classic all-around ratio — manageable on flats and hills with good skid patch coverage. Higher ratios (48/15 = 3.2:1) favor flat terrain and speed. Lower ratios (42/17 = 2.47:1) are better for hilly cities. Track riders typically use 48/14 or higher.