As seems to be typical for a bike from the 80s, my 1988 2NX SRX600 has shitty, wooden brakes. This is the result of poor hydraulics, particularly the ratio between the master cylinder size and the total caliper piston area, which dictates the mechanical advantage of the system. The SRX6 has a 15.8mm master cylinder (5/8″, 195.9mm^2 area) and a single four piston caliper acting on a 320 mm floating disc. I wasn’t able to measure the caliper piston sizes at this point. Improving the hydraulic ratio can be done by either using a caliper with a larger piston area, or a master cylinder with a smaller piston bore.
Master cylinder piston size isn’t something that is typically listed, so it took a bit of searching to discover that NSR150 master cylinders are 11mm (piston area is 95mm^2). I got one in decent condition off eBay for around AU$43 delivered. Fitment was fairly straight forward. Due to the increased lever travel I had to rotate the switchblock to give a bit more clearance. Also, there is no mirror mount, so I will use a bar clamp mirror mount. The brakelight switch doesn’t fit, so I will have to find a suitable switch.
Performance is now excellent. Very nice initial bite, and plenty of power for one to two finger use. Lever travel is good – while I could squeeze the lever in enough to get in the way of my fingers during testing, the braking power is good enough that this would only happen if I had some serious brake fade happening, or I was doing a stoppie. I will probably upgrade to braided brake lines at some point, but at the moment it just isn’t really necessary, as there isn’t too much flex apparent.
Overall, A highly recommended and successful upgrade.