What are skid patches on a fixed gear bike?

Skid patches are the specific points on your tire that contact the ground when you lock your legs and skid to slow down on a fixed gear bicycle. The number of patches depends on your gear ratio - specifically the chainring and cog tooth counts. More skid patches means the wear is distributed across more points on the tire, resulting in longer tire life.

Why do skid patches matter for fixed gear riders?

Skid patches directly determine how quickly your rear tire wears out. With fewer skid patches, the same spots on the tire contact the road every time you skid, leading to rapid flat spots and frequent tire replacements. A gear ratio with many skid patches spreads wear more evenly, saving money and improving safety by avoiding dangerously thin spots on the tire.

How are skid patches calculated?

Single-foot patches equal cog teeth divided by GCD(chainring, cog). Reduce the gear fraction: if its chainring numerator is odd, the both-foot count doubles; if even, it stays the same. Thus 48/17 gives 17 for both counts, while 49/17 gives 17 single-foot and 34 both-foot patches.

What is the difference between single-leg and ambidextrous skid patches?

Single-foot counts describe one repeated crank position. Both-foot counts also include the opposite crank position, half a turn away. That adds new contact points only when the reduced gear fraction has an odd chainring numerator. These are theoretical counts, not braking instruction or a tire-life guarantee.

What gear ratios give the most skid patches?

Gear ratios where the chainring and cog share a GCD of 1 (coprime numbers) produce the maximum number of skid patches, equal to the cog tooth count. For example, 49/17 gives 17 patches. Avoid ratios where both numbers share large common factors - like 48/16 (GCD of 16), which gives only 1 skid patch. Prime-number cogs such as 13, 17, and 19 often yield the best results.

How many skid patches do I need for acceptable tire wear?

As a general guideline: fewer than 5 skid patches means rapid, uneven tire wear that will require frequent replacements. Between 5 and 10 patches is acceptable for moderate riding. 10 to 15 patches is good for regular commuting. More than 15 patches is excellent - your tire wear will be spread very evenly. Urban riders who skid frequently should aim for at least 10 patches.

Can I improve my skid patches without changing my gear ratio?

The theoretical patch count is fixed by the tooth counts and whether one or both crank positions are counted. Tire care and proper braking matter more than maximizing that number. Inspect your tread and replace a damaged or worn tire; a high patch count does not make it safe.

What is the best chainring and cog combination for a fixed gear bike?

The best combination depends on your terrain and riding style, but for maximizing skid patches while maintaining a rideable gear ratio, popular choices include 49/17 (2.88 ratio, 17 patches), 49/15 (3.27 ratio, 15 patches), and 47/17 (2.76 ratio, 17 patches). These all use coprime numbers that maximize skid patches while providing practical gear ratios for urban riding.

Does a higher gear ratio mean fewer skid patches?

Not necessarily. Skid patches depend on the mathematical relationship between chainring and cog teeth, specifically their greatest common divisor. A high ratio like 50/17 (GCD 1) gives 17 patches, while a lower ratio like 48/16 (GCD 16) gives only 1 patch. The key is choosing numbers that are coprime (share no common factors), regardless of the resulting ratio.

How do skid patches affect track cycling vs. street riding?

The mathematics is the same, but a gear choice must suit the riding context and applicable rules. A patch count describes possible tire contact positions; it does not establish a safe braking setup. For road use, use properly maintained brakes and follow local requirements.

Skid Patch Calculator for Fixed Gear Bikes

Enter your chainring and cog tooth counts to calculate a fixie gear ratio and its repeating tire contact points. Compare single-foot and both-foot counts; patch count alone cannot predict tire life.

Fixed gear ratio and skid patch chart

Similar gear ratios can produce different patch counts. These examples use the same calculation as the tool. For speed at a chosen cadence or gear inches, use the gear ratio calculator.

Fixed gear tooth combinations and theoretical skid patch counts
Chainring / cog	Gear ratio	Single-foot patches	Both-foot patches
48/16	3.00	1	2
48/17	2.82	17	17
49/17	2.88	17	34
46/16	2.88	8	16

48/16
Gear ratio
3.00
Single-foot patches
1
Both-foot patches
2
48/17
Gear ratio
2.82
Single-foot patches
17
Both-foot patches
17
49/17
Gear ratio
2.88
Single-foot patches
17
Both-foot patches
34
46/16
Gear ratio
2.88
Single-foot patches
8
Both-foot patches
16

This is a mathematical reference, not braking instruction. Use properly maintained brakes and inspect tires for damage; skidding is not a substitute for controlled braking.

What Are Skid Patches?

Skid patches are the specific points on your rear tire that make contact with the road surface when you lock your legs to slow down on a fixed gear bicycle. Because the drivetrain on a fixie mechanically links the pedals and rear wheel without freewheeling, the tire contacts the ground at predictable, repeating positions determined by your gear ratio.

The number of skid patches is a function of the chainring and cog tooth counts - specifically, the cog teeth divided by the greatest common divisor (GCD) of both values. A higher number of skid patches means wear is distributed across more points on the tire. Actual wear also depends on braking, surface and tire condition.

Why Skid Patches Matter for Fixed Gear Riding

A low patch count concentrates repeated abrasion on fewer points. A higher count spreads those potential contact points, but it does not specify a safe tire lifespan or stopping distance. Replace damaged or worn tires rather than relying on a favorable count.

Choosing the right gear ratio isn't just about cadence and speed - it's also about practical tire economics and safety. A flat-spotted tire has less grip in wet conditions and is more prone to blowouts. Understanding skid patches helps you make an informed decision when building or modifying your fixed gear setup.

How to Maximize Your Skid Patches

Gear Ratio Selection

• Use coprime numbers: Choose chainring and cog counts that share no common factors
• Prime cogs: Cogs with prime tooth counts (13, 17, 19) tend to maximize patches
• Avoid even/even: Two even numbers always share at least a factor of 2
• Odd chainrings: 47 and 49 tooth chainrings pair well with most cogs

Tire care and braking

• Both-foot count: The second number describes theoretical contact points, not a riding recommendation
• Inspect the tread: Replace a damaged or worn tire rather than redistributing its wear
• Front brake: Adding a front brake reduces reliance on skidding
• Harder compounds: Fixed gear-specific tires use more durable rubber

Understanding the Math

The formula for skid patches is straightforward: Single-leg patches = Cog teeth ÷ GCD(Chainring, Cog). The GCD (Greatest Common Divisor) is the largest number that divides evenly into both the chainring and cog tooth counts.

Reduce the chainring/cog fraction first. For both-foot patches, if the reduced chainring count is odd, you double it because swapping the lead foot hits new parts of the tire. If the reduced chainring count is even, the both-foot count stays the same because the opposite foot lands on the same patch sequence again.

For example: a 49/17 setup has GCD(49, 17) = 1, so you get 17 ÷ 1 = 17 single-leg patches. Since 17 is odd, ambidextrous gives you 17 × 2 = 34 patches. In contrast, 48/17 stays at 17 patches for either count because its reduced chainring count is even.

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Explore Brand Size Charts & Guides

Gear	Ratio	Single-leg	Ambidextrous
47/19	2.47	19	38
49/19	2.58	19	38
47/18	2.61	18	36
49/18	2.72	18	36
47/17	2.76	17	34
49/17	2.88	17	34
47/16	2.94	16	32
49/16	3.06	16	32
47/15	3.13	15	30
49/15	3.27	15	30

Skid Patch Calculator for Fixed Gear Bikes

Fixed gear ratio and skid patch chart

What Are Skid Patches?

Why Skid Patches Matter for Fixed Gear Riding