Brakes - very hard, little travel

Ok, so I believe I have succesfully bled my brake lines, but I need a sanity check. The feel REALLY hard. I took a ruler to the master cylinder shaft, and it appears to only move about a quarter-inch between open and closed. By rocking the wheel with my hand I can feel that it is free with the brakes off, and that the brakes definately are gripping when applied. But they're going to be VERY touchy.
When I look at the pads, they appear to be almost touching the brake disc (rotor?) when open... i can barely see any gap. I can't really visually see the pads move when I pump the brakes.
1) Does this all sound like a normal and healthy system?
2) How much fluid should I leave in the reservoir?

prkaye said:

Ok, so I believe I have succesfully bled my brake lines, but I need a sanity check. The feel REALLY hard. I took a ruler to the master cylinder shaft, and it appears to only move about a quarter-inch between open and closed. By rocking the wheel with my hand I can feel that it is free with the brakes off, and that the brakes definately are gripping when applied. But they're going to be VERY touchy.
When I look at the pads, they appear to be almost touching the brake disc (rotor?) when open... i can barely see any gap. I can't really visually see the pads move when I pump the brakes.
1) Does this all sound like a normal and healthy system?
2) How much fluid should I leave in the reservoir?

Click to expand...

Phil, sounds like you have a good brake system--all is normal.

The brakes won't be touchy because the pads and rotors are so small. You only need enough fluid to be sure the master cylinders don't go dry.

cylinder spring

I agree with Sam, sounds like you have completed the brake installation successfully.

However, the cylinders that come with the kit have a reputation for not fully opening when you let off the brake pedal. That might be the reason you're not seeing any light between the pads and the wheel. Some folks use a spring over the piston that applies constant pressure so the piston stays in the out position when the brakes are not engaged. There are some pics on one of the forums. I use them and it helps extend brake pad life. You can probably hear it if you have the problem. You can usually hear the friction when you move the plane with brakes off. It's fairly common but doesn't seem to affect everyone. Just a heads up.

I actually have installed a 3" compression spring over the shaft of each master cylinder, with a couple of large washers at the bottom. I did this simply as a safety precaution because I'd heard about the troubles with them sticking. The springs are only in very slight compression when the brakes are open, but this seems to be enough so that they are always pulling open on their own after I apply the brakes.

I really did reef hard on that fitting to stop the leak in that pipe thread. Although the leak appears to have stopped, this is nagging on me. I worry that I have over-stresseed the fitting and created a time-bomb, and that the threads will fail under the stress at some point. Is this worth worrying about?

Parts list

There is a wonderful article on VAF that describes a fix that I can't find... We had this problem.
Fix involves installing a plastic bushing, sprint and collar on each master cylinder.

http://websites.expercraft.com/PHVII/index.php?q=log_entry&log_id=19304

I used the following from McMaster Carr
www.mcmaster.com/

(1) Pkg 6389K625
Nylon Bearing Flanged, for 3/8" Shaft Dia, 1/2" Od,
3/8" Length, Packs of 5 $2.26 Pkg

(1) Pkg 9657K115
Steel Compression Spring Zinc-Plated Spring-Tempered, 3"
L, 1/2" Od, .047" Dia, Packs of 12 $6.00 Pkg

(4) Ea. 9946K13
Aluminum Set Screw Shaft Collar 3/8" Bore, 3/4"
Outside Diameter, 3/8" Width $1.91 EA.

MauiLvrs said:

There is a wonderful article on VAF that describes a fix that I can't find... We had this problem.
Fix involves installing a plastic bushing, sprint and collar on each master cylinder.

http://websites.expercraft.com/PHVII/index.php?q=log_entry&log_id=19304

I used the following from McMaster Carr
www.mcmaster.com/

(1) Pkg 6389K625
Nylon Bearing Flanged, for 3/8" Shaft Dia, 1/2" Od,
3/8" Length, Packs of 5 $2.26 Pkg

(1) Pkg 9657K115
Steel Compression Spring Zinc-Plated Spring-Tempered, 3"
L, 1/2" Od, .047" Dia, Packs of 12 $6.00 Pkg

(4) Ea. 9946K13
Aluminum Set Screw Shaft Collar 3/8" Bore, 3/4"
Outside Diameter, 3/8" Width $1.91 EA.

Click to expand...

The set screw used on the collar will scratch the shaft of the master cyl. Be sure to polish it out before rebuilding the unit. You don't really need the collar to lock on the shaft. The mounting bolt will hold it in place, you just shim it up with washers till it has the rebound that you want then install the mounting bolt.