Brake Line Sizing Calculator
Design and validate your brake system. Select master cylinder bore, front and rear caliper piston configuration, pedal ratio and driver input force to calculate hydraulic ratio, line pressure, axle clamp force, brake bias and recommended AN line size.
Safety critical system. All results are for reference only. Always have brake system modifications verified by a qualified motorsport engineer or vehicle inspector before track use. Never compromise on brake system integrity.
Master Cylinder Bore
MC bore 19.05 mm → area 285.02 mm²
Front Caliper (per side)
Total piston area (both sides): 9919.0 mm²
Rear Caliper (per side)
Total piston area (both sides): 4536.5 mm²
Typical street: 4–5 : 1 | Race: 3–4 : 1
400 N ≈ 41 kgf foot force
Brake System Results — 19.05mm MC
Line Pressure
916
PSI
Line Pressure
63.15
bar
Front Clamp
62.6
kN (axle)
Rear Clamp
28.6
kN (axle)
Hydraulic Ratio
25.36
: 1
Front Bias
68.6
%
Rear Bias
31.4
%
Rec. Line Size
AN-3
Brake Line Size Guide
AN-3 ← Recommended
Bore: 4.8mm
Standard single circuit, most motorsport brake lines. OEM replacement.
AN-4
Bore: 6.4mm
Dual circuit master cylinders, large caliper setups, or long line runs.
AN-2
Bore: 3.2mm
Very short runs, clutch slave only. Not recommended for brakes.
Methodology
Hydraulic Ratio: Total caliper piston area ÷ master cylinder area. A higher ratio gives more clamp force but requires more pedal travel. Typical ratio: 6–12:1 for road/track cars.
Line Pressure: P = (Pedal Force × Pedal Ratio) / MC bore area. Higher MC bore = lower pressure for same pedal force — softer pedal feel. Lower MC bore = higher pressure, firmer pedal, less travel.
Brake Bias: Front 65–80% is typical for most track cars. Rear-heavy bias (below 60% front) causes rear wheel lockup under braking — extremely dangerous. Adjust with a bias bar or proportioning valve.
Line Size: AN-3 (4.8mm bore) is the standard for nearly all motorsport brake lines. AN-4 is used for longer runs or dual-circuit systems. Oversizing the line does not improve braking — it increases compressibility and gives a spongy pedal.