Find the right chainring × cog combo. Live 7×7 matrix — tire data from BMXultra.
Actual measured OD — data from bmxultra.com
GEAR RATIO
2.75
GEAR INCHES
55.0″
ROLL OUT
172.8″
AT 90 RPM
23.7km/h
SETUP RATING
HIGH — Speed focus. Requires strong first-straight power.
values = gear inches
| COG↓ / CR→ | 41T | 42T | 43T | 44T | 45T | 46T | 47T |
|---|---|---|---|---|---|---|---|
| 13T | 63.1 | 64.6 | 66.2 | 67.7 | 69.2 | 70.8 | 72.3 |
| 14T | 58.6 | 60.0 | 61.4 | 62.9 | 64.3 | 65.7 | 67.1 |
| 15T | 54.7 | 56.0 | 57.3 | 58.7 | 60.0 | 61.3 | 62.7 |
| 16T | 51.3 | 52.5 | 53.8 | 55.0 | 56.3 | 57.5 | 58.8 |
| 17T | 48.2 | 49.4 | 50.6 | 51.8 | 52.9 | 54.1 | 55.3 |
| 18T | 45.6 | 46.7 | 47.8 | 48.9 | 50.0 | 51.1 | 52.2 |
| 19T | 43.2 | 44.2 | 45.3 | 46.3 | 47.4 | 48.4 | 49.5 |
Gear Inches = (chainring ÷ cog) × actual tire OD. Roll Out = Gear Inches × π. Data: bmxultra.com.
RATIO SPECTRUM
SHOP MATCHING HARDWARE
Chainring ÷ cog. A 44×16 = 2.75 — rear wheel turns 2.75× per crank rev. Higher = more top speed, harder to accelerate from the gate.
Ratio × actual tire OD in inches. Standard way to compare setups across wheel sizes. 44×16 on Maxxis Torch 20×1¾ = 53.6" gear inches.
Gear Inches × π. Distance traveled per crank revolution. Directly comparable across timing systems and gearing databases worldwide.
The 7×7 grid shows gear inches for ±3 teeth in each direction. Sweet spot (green) = 52–58". Classic 44×16 benchmark = ~55 gear inches.