brake upgrade

bearshawk wrote: what is your MC from?? i would definitely be intersted!

ZX11/GPZ1100/ZG1000 are all the same, but I don't remember if this one is off a ZX11 or a 95-96 GPz1100.

I suggest that you never install a used master cylinder until after you rebuild it. I didn't one time and ended up low siding when I lost my front brakes.

531blackbanshee wrote:

steell wrote:

531blackbanshee wrote: laymans terms.
too small a master cylinder may not apply enough force to stop you.
too big may apply too much force and cause you to lock up the wheel.

hth,

leon

You do realize that you have that backwards?
Smaller master cylinder = more force
Larger master cylinder = less force
At the caliper.

thanks for clearing that up.
leon

It helps when you've spent a few years working on different hydraulic systems,

To explain for anyone else reading.

I'm going to make some generalizations to avoid boring people with the math.

I'll assume you have a KZ with a single 12" brake rotor, a 50mm caliper single piston, and a 1/2" master cylinder bore. You squeeze the brake handle, you push the 1/2" piston 1/2", and you generate 500 lbs of stopping force. Now you bolt on a second 12" rotor and a second 50mm single piston caliper, but keep the same 1/2" master cylinder. Now when you squeeze the brake lever the piston has to travel twice as far (because it's feeding two calipers), and you're applying 500 lbs of stopping force to each disk, for a total of 1000 lbs of stopping force, so the front wheel locks up.

(Warning, slight exaggeration ahead)

Since locking the front wheel is not an ideal outcome, you decide to reduce the stopping power a bit, and you want to reduce the lever travel to what it originally was, so you install a larger master cylinder. So you find a 5/8" bore master cylinder, and install it. Now because of the larger diameter (and larger area of the piston) a 1/2" movement of the piston moves almost twice as much fluid, so the lever only moves half as far. And because you have increased the area of the piston, the 30 lbs of lever force that formerly was exerted on 1 sq. in. of piston is now spread over two sq. in. of piston, so where you did have 30 psi going to each caliper you now have 15 psi.
30 psi on 1 sq in vs 30 psi spread over two sq in (15 lbs per sq in). move more fluid and lose power, move less fluid and gain power. Look at a hydraulic jack, little tiny pump and big cylinder lets you lift tons with one hand, slowly.

Earthmoving equipment uses variable displacement hydraulic pumps, and often have switches to go from large displacement, high flow, high speed, low power, to small displacement, low flow, low speed, much power.