Brembo Front Radial Brake Master Cylinder 15rcs 110a89730

The Brembo 15RCS front radial brake master cylinder is engineered exclusively for handlebars with a 1-inch (25.4 mm) diameter. This is a custom-made variant by Brembo for the world of Custom, Cafe Racer, and Cruiser motorcycles. It allows you to bring the maximum hydraulic performance and adjustments derived from MotoGP (such as the Ratio Click System with variable interaxle 18-20 mm) to bikes that structurally feature oversized handlebars, instead of the classic 22 mm sport handlebars.

• Clamping Bracket: 1" (25.4 mm) diameter for custom handlebars.
• Hydraulics: 15 mm internal piston, perfect for high-performance single-disc systems or dual-disc systems equipped with floating brake calipers.
• Features: CNC-finished forged body with hard oxidation treatment, anti-fall articulated lever, and integrated mechanical switch for the street stop light.

This master cylinder is predominantly mounted on the entire range of Harley-Davidson and specific Triumph Classic or Japanese Cruiser models that use the 1-inch (25.4 mm) handlebar as standard. The application covers a very wide time range, approximately from the '90s to today, provided that the braking system meets the 15 mm hydraulic configuration (Single Disc or Floating Dual Disc).

The most frequent models on which it is installed as an upgrade include:

HARLEY-DAVIDSON (Models without standard Cruise Control)

• Sportster 883 / 1200 (Iron, Forty-Eight, Nightster, Custom, Roadster): from 1988 to 2020 (A very popular application to improve the sponginess and lack of power of the standard front brake).
• Dyna (Street Bob, Low Rider, Wide Glide, Fat Bob): from 1991 to 2017 (Both in single-disc and dual-disc configuration of those years).
• Softail (Standard, Heritage, Slim, Fat Boy): from 1984 to today (Note: compatible with models equipped with ABS, but requires checking the electrical stop switch wiring on modern blocks).
• Street 750 / Rod: from 2014 to 2020.

TRIUMPH (Modern Classic range with 1" handlebar)

• Bonneville T120 / T120 Black: from 2016 to today (Great upgrade to manage the standard calipers).
• Bonneville T100: from 2017 to today (Single-disc system).
• Speedmaster / America (865cc and 1200cc): from 2002 to today.
• Thruxton 900 (Carburetors / Injection): from 2004 to 2015 (The subsequent 1200 versions use different handlebars or clip-ons).

JAPANESE CUSTOM & BOBBER

• Honda VT 750 Shadow / CMX 500 Rebel.
• Yamaha XVS 650 / 1100 Dragstar and XV 950 Bolt.
• Kawasaki VN 900 Vulcan.

Mounting Warning: Being Custom bikes, the original electrical blocks (especially the massive ones on Harley-Davidson) leave very little space on the handlebar. For installing the Brembo RCS master cylinder, it is almost always necessary to use mirrors with aftermarket mounts or a special clamp with an integrated thread, in addition to checking the lever's clearance near the original switch blocks.

This warning means that the Brembo brake master cylinder has a very different shape from the original one on your bike, and to mount it correctly, you will face two small "space" issues on the handlebar. Here's what it means in detail, explained in simple words:

1. The Mirror Issue (The "Clamp")

On Custom bikes (especially on Harley-Davidson), the right mirror is usually screwed directly above the original brake structure or on the switch block.
• What changes with Brembo: The Brembo master cylinder does not have the hole to screw the original mirror.
• The solution: To avoid being without a right mirror, you will need to buy an accessory called a "threaded clamp." It is simply the rear clamp of the brake master cylinder (the metal half-moon with the two screws that tighten the master cylinder on the handlebar) that tightens the master cylinder on the handlebar but also has a threaded hole to screw the mirror into. Alternatively, you will need to use a bar-end mirror.

2. The Space Issue (The "Electrical Blocks")

The switch blocks on Custom bikes (where the ignition button, turn signals, etc., are located) are very large and "chunky."
• What changes with Brembo: The Brembo master cylinder is a sporty/racing master cylinder. It has a compact aluminum body but a lever that develops differently from the stock one.
• What you risk: If the original buttons are too thick, the Brembo lever might hit them when you press it, or you might not be able to bring the master cylinder close enough to the throttle grip, forcing you to ride in an uncomfortable position.

In summary, what do you need to do in practice?

Before buying the master cylinder, or as soon as you take it to the mechanic, you need to check that there is enough linear space on the handlebar to accommodate the throttle grip, the original buttons, and the new Brembo master cylinder, knowing already that the right mirror will need to be fixed in a different way than it is now.
To give you a precise idea: what mirrors do you currently have? Are they the original ones inserted in the blocks, or do you already have aftermarket mirrors (perhaps at the end of the handlebar)?

SKU	110A89730
ID	70321