Banjo Bolts for Brake Calipers & Master Cylinders The Right Bolt for a Leak-Free Hydraulic Connection
A banjo bolt is the threaded fastener that secures a brake hose or hard line to a caliper, master cylinder, or ABS unit. It passes through the hollow eye of a banjo fitting, threads directly into the port, and clamps two copper sealing washers against the mating surfaces to form a sealed hydraulic connection.
How to Identify Your Banjo Bolt Size
Measure three things off the old bolt: thread diameter (e.g. 10mm or 3/8"), thread pitch (threads per inch for SAE, mm between threads for metric — a thread gauge makes this foolproof), and shank length. Common brake sizes: M10x1.0 and M10x1.5 (most Asian/European calipers), M12x1.0, 3/8"-24 and 7/16"-24 (American), 1/2"-20. Every product page lists all three measurements.
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.
Installation Tips for a Leak-Free Seal
Always use 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, torque to your vehicle's spec (typically 25–35 ft-lbs for M10 caliper bolts — verify in your service manual), and bleed the brakes afterward. Never wrap banjo bolt threads with PTFE tape; the seal is at the washers, not the threads.
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.
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.
