REFLECTOR: Toe Brakes, Back Bleeding

Alex Balic velocity_pilot at verizon.net
Sun Jun 10 09:56:19 CDT 2007


Hey Ron- I am not sure how you will be able to remove all of the air from
your bleeder is not at the high point- if you have been able to do that,
then you are very lucky! - if it turns out that you still have some air in
there, you might want to remove the caliper from the wheel, turn it so that
the bleeder is up, bleed them that way, and then without of course
disconnecting them, put them back on the axle...

 

Alex

 

  _____  

From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Ron Brown
Sent: Sunday, June 10, 2007 8:03 AM
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: Toe Brakes, Back Bleeding

 

I had one brake that was soft and had to be pumped.  I thought it was a bad
master cylinder and got a new one - same problem.  

 

Some one had mentioned that air can get trapped in the calipers if they were
not turned such that the bleed port was down and the fluid connection at the
top.  In other words, take the caliper loose from the gear leg and orient it
vertically.  I back bled my brakes from the bottom to the top.  Problem
fixed.

 

I bought the oil can back bleeder from MATCO.  I have seen similar oilers in
the hardware stores.  

----- Original Message ----- 

From: Hiroo Umeno <mailto:humeno at microsoft.com>  

To: Velocity Aircraft <mailto:reflector at tvbf.org>  Owners and Builders list 

Sent: Sunday, June 10, 2007 12:21 AM

Subject: REFLECTOR: Toe Brakes, again...

 

The second installment of the ongoing brakes saga. 

 

My setup is a factory toe-brake kit with Matco brakes on FG SUV (std
fuselage, std wing).  My brake lines are a combination of the hard aluminum
line from forward bulkhead to gear bulkhead and the factory provided
nylaflow line, the rest of the way.

 

It was a rainy day today and I decided to bleed the brake system.  I drained
the system of fluid, then re-filled it.  I generally do this "bottom up"
where I start filling the fluid from the lowest point in the system (bleed
valve at the gear) and fill the fluid until the reservoir is full.  My
thinking is that going bottom up will ensure that there are no trapped
bubbles in the system.

 

The brake is way too "soft" for my liking, still.  There is quite a bit of
toe motion when pushing on the brakes.  It is a lot more than what I am used
to on Cessnas and Pipers.  On those, I get the "push back" almost as soon as
I get my toe on the brakes and there is very little room to Squeeze.  On my
plane, it feels like I am displacing a lot of fluid through the master
cylinder.  Shouldn't there be very little movement on the pedals?  The way I
understand the system work is that there should be very little fluid
movement and the brake should work by pressurizing the system and not
displacing.

 

Curiously, I found that the passenger side left brake feels "taught".  All
the rest felt rather mushy.

 

Aside from bleeding again to check for air bubbles, what else should I
check?  There are no leaks in the system along the way, either.

 

Hiroo

 


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