The NGW Project Bike. Brake rebuild

[Hondanaut]

Hey Octane, this is the best explanation of cylinder rebuild I've ever come across. Wish I had this when I was dealing with my CB900 -- the Clymer's manual is terrible on this. Thanks very much for the careful, detailed, great job.
-Scott

BTW, now I have a further question... can I use another brake handle assembly, say, from an old CB750? It's just a little thing, but I don't really like the tall white plastic reservoir.

[octane]

Thanks Hondanaut.


.....mmmmm. I couldn't tell.
Three things to consider:

1..the volume (cc) of brake fluid moved.

It would have to be the same


Let's say it is the same.
Then:

2..the stroke length of the brake piston

Longer stroke/smaller diameter = longer movement of handle.
but more 'leverage' in the brake action (lower 'gear'ed)

3..the diameter of the brake piston

Shorter stroke/larger diameter= shorter movement
but less leverage in the brake action (higher gear'er)


.so; donno.

[ncondit]

octane

does the rear master cylinder come apart like the front one does? or is there another pictoral some where i can look at.

thank you very much fatandold!!!

[octane]

octane
does the rear master cylinder come apart like the front one does?

Yep. (Allmost) exactly as the front one.

or is there another pictoral some where i can look at...

Oii !
I never posted that one....did I ??!!?

[ncondit]

octane
thanks very much, the one you posted for the front master cylinder was very great. thanks again ----fatandold!!!

[Jwinger]

was going to rebuild mine am starting my bobber now and that was on my list , but i thank ill take ur advice and have some one else rebuilt the break calibers i have never done it , also beautiful project bike , jwinger , columbia sc

[motnick]

How about a rundown of the rear brakes? Does that exist already?

[Frenchy]

How about a rundown of the rear brakes? Does that exist already?

I don't believe one does, & I just so happen to be getting ready to do a 76 rear caliper.. I will attempt to do a detailed "How to" while doing it. But I must say that it won't be as good as Octane's!!

[octane]

Ohhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh forgot about that.


Long ago I promised to do a similar thing on the rear brake.
I DO have have the pics on file and I WILL do it within the next few days
as I FINALLY (Phew) have some time of,
(as of today)
after being ******* busy for a while.

Promise!

[Whiskerfish]

Bout time you come back to work. you keep this up and we are gonna have to doc your pay

[Frenchy]

DITTO!!!!!






I'm just glad I don't have to do the pictorial!!

[octane]

Bout time you come back to work. you keep this up and we are gonna have to doc your pay

Oh no!
That would force me to sell my private Gulfstream jet.

[morganfrmn]

so where do i buy all these parts and what do you recommend...

[Whiskerfish]

Three posts above this one is one by Frenchy. In the bottom left of his post is a banner for Crescent Moon Cycles. Click on that and look for your parts

[Sidecar Bob]

can I use another brake handle assembly, say, from an old CB750? It's just a little thing, but I don't really like the tall white plastic reservoir.

I think you mean the master cylinder. If you want to replace your master cylinder with one from another model there are 3 considerations:

1) Bore diameter. Master cylinders for models with dual discs must displace twice the fluid for a given lever stroke than ones for single disc models. If you use a dual disc MC with only one caliper the lever will have less travel than it should and modulation of the brake will be more difficult. If you use a single disc MC with 2 calipers it will need twice the lever movement to apply the brake and in some cases the lever may reach the handlegrip before the brake is fully applied. Single disc MCs are usually 1/2" bore and dual disc MCs are 5/8" (see explanation below)

2) Handlebar diameter.

3) The angle the reservoir sits at. Some models (including customs) have master cylinders with the reservoirs at an odd angle so that they sit level when mounted on the oddly bent handlebars.

Explanation:
If you do the math you will find that a 5/8" circle has approx. twice the area of a 1/2" circle. This means that if you use a 5/8" master with one caliper it will only have half of the lever stroke that a 1/2" master would have.

No matter how many pistons a caliper has it still has to move the pads the same distance in order for them to grip the disc. That's why dual piston calipers have smaller pistons. Multiple pistons simply allow the use of longer, narrower pads that can concentrate the grip nearer to the edge of the disc where the leverage is better.

The ratio of the area of the master cylinder piston to the area of the caliper piston(s) is what matters. If the master cylinder's area is smaller the lever will need to travel farther to move the pads against the disc. The longer lever travel is like a lower gear ratio: a larger amount of movement at the input produces a smaller amount of movement at the output but with less force needed to produce the movement.
Therefore, if you use a dual caliper master cylinder with only one caliper the lever will travel less distance and more force will be required to stop the bike.

This won't matter if you have a grip like a gorrilla, but for those of us with normal grip it can mean the difference between stopping or hitting something.

Also, most people don't realize that brake levers are wear items. The bump that presses on the piston can eventually wear away so that it can no longer push the piston far enough to fully apply the brake. This is usually indicated by excessive play when the lever is released. A poorly coppied aftermarket lever or the wrong lever for the master cylinder can cause the same problem. It can sometimes be remedied by drilling & tapping a hole in the lever's bump and putting a small round headed screw in, but replacing the lever with a new one is a better option.