Banjo Bolts for Brake Calipers & Master Cylinders
A banjo bolt is the hollow threaded fastener that connects a brake hose or hard line to a caliper, master cylinder, or ABS unit. It passes through the eye of a banjo fitting, threads into the port, and clamps two copper crush washers against the mating surfaces to form a sealed, leak-free hydraulic connection. Get the thread size, pitch, and length right and the joint seals for the life of the vehicle — get one of them wrong and it either won't start or won't stop leaking.
How to Pick the Right Banjo Bolt (3 Measurements)
Measure these three things off the old bolt before you order: thread diameter (e.g. 10mm or 3/8"), thread pitch (mm between threads for metric, threads-per-inch for SAE — a thread gauge makes this foolproof), and shank length. Every product page lists all three so you can match exactly.
Banjo Bolt Size Chart
| Thread size | Pitch | Standard | Common application |
|---|---|---|---|
| M10 x 1.0 | 1.0 mm | Metric | Many Asian & European calipers |
| M10 x 1.25 | 1.25 mm | Metric | Japanese calipers & master cylinders |
| M10 x 1.5 | 1.5 mm | Metric | European calipers, common banjo size |
| M11 x 1.25 | 1.25 mm | Metric | Select European brake systems |
| M12 x 1.0 | 1.0 mm | Metric | Larger metric caliper ports |
| 3/8"-24 | 24 TPI | SAE | American calipers & wheel cylinders |
| 7/16"-20 | 20 TPI | SAE | American master cylinders |
| 7/16"-24 | 24 TPI | SAE | American brake & hydraulic ports |
| 1/2"-20 | 20 TPI | SAE | Larger American hydraulic fittings |
Shop by size: M10x1.0, M10x1.25, M10x1.5, M11x1.25, M12x1.0, M12x1.5, 3/8"-24, 7/16"-20, 7/16"-24, 1/2"-20 — all sold in bags of five.
Typical Torque Specs
Always confirm the figure in your vehicle's service manual — these are common starting ranges, not a substitute for spec:
| Bolt size | Common torque range |
|---|---|
| M10 (caliper banjo) | ~25–35 ft-lbs |
| M12 (larger metric) | ~30–40 ft-lbs |
| 3/8"-24 / 7/16" SAE | ~25–35 ft-lbs |
Installation Tips for a Leak-Free Seal
Always fit new copper crush washers on both sides of the banjo fitting — they work-harden and won't reseal once compressed. Thread the bolt by hand first to avoid cross-threading, torque to spec, and bleed the brakes afterward. Never wrap the threads with PTFE tape; the seal is at the washers, not the threads. Need washers? Grab them from brake line fittings.
FAQ
Are banjo bolts universal?
No — thread diameter, pitch, and length must all match your caliper or master cylinder port. An M10x1.0 will start in an M10x1.5 port but will strip it.
Single or double banjo bolt?
A single-port bolt feeds one hose; a double-banjo (two stacked eyes, longer shank) feeds two lines from one port — common on shared front circuits. Match the number of eyes on your original.
Can I reuse copper washers?
Not reliably. They're a few cents each — replace them every time the joint is opened.
Why is my banjo fitting still leaking?
Usually reused washers, a scored sealing surface, or under-torque. Clean both faces, fit new washers, and re-torque to spec.
