[Fot] Brake balance bar

McKearn McKearn mckearn2 at gmail.com
Sun May 28 13:56:23 MDT 2017 

Hi.
  I have not rebuilt the calipers I have just turned the rotors and put in
new pads. As I mentioned earlier I found that the balance bar is the source
of the problem. Specifically that it is flipping up and down as viewed from
the front of the car when pedal is depressed. It seems to be occasionally
catching or sticking in a cocked position (one side up, the other side
down).  I really don't think cylinder size has anything to do with this
problem as I have used this car  daily (summers) for ten years and have run
two track days at BFR with the same brake system and settings.  I suspect
the wear argument is probably the answer and I will check that out later
today.
                                                Thanks.  P.J.

On Sat, May 27, 2017 at 11:36 PM, Scott Janzen <sjanzen at me.com> wrote:

> I went one size larger on my gt6 for the front brakes' master for exactly
> the reasons you described.  You need to move a lot more fluid to displace a
> 1.5" caliper piston than you do to move a small rear wheel cylinder piston.
>
> The problem is, you lose mechanical advantage when you go to a larger
> master cylinder. With one size up on the master cylinder for the front
> brakes I really have to stand on the pedal at the end of the straight.
> An alternative might be to go to a bias valve for the rears to simply
> reduce fuel flow there.
> I'm puzzled, though, because your email indicates it used to work fine
> with the current set-up?
>  Have you rebuilt the front calipers, checked all the lines, etc?
> Sent from my iPhone
>
> On May 27, 2017, at 11:32 PM, McKearn McKearn via Fot <fot at autox.team.net>
> wrote:
>
> Thanks for the replies.
>  O.K. assuming a master cylinder is the wrong size. Which way to go? I
> already have two 5/8 diameter cylinders. As far as I know you can't go
> smaller so I'll need to have one larger. As it is I like a slightly softer
> pedal and the front seams to have plenty of travel and a good feel. So if I
> want more travel for the back I would need a smaller cylinder right???
>  By the way it was me who didn't bother to calculate the proper cylinder
> size but I did get some advice from one or more expert Triumph racers...
>                                                                   P.J.
>
> On Sat, May 27, 2017 at 1:05 PM, John Hasty via Fot <fot at autox.team.net>
> wrote:
>
>> We use a 1" Willwood dual MC with apportion valve for rear.  Works great.
>>
>> Sent from my iPhone
>>
>> On May 27, 2017, at 1:43 PM, "Duncan Charlton via Fot" <
>> fot at autox.team.net> wrote:
>>
>> On a related note, the Morgan Plus 4 I used to race seemed to have too
>> much braking force in the rear.  There was a hydraulic brake balance lever
>> but that had already been adjusted all the way toward greater front brake
>> bias when I bought the car.  I replaced the rear wheel cylinders with 3/4”
>> bore TR6 items (perfect fit to replace the 7/8” Morgan items).
>> Unfortunately it didn’t cure that particular problem, but it does show
>> another way to tune the force of your rear brakes.
>>
>> Duncan Charlton
>> 1121 Lower Elgin Rd
>> Elgin, Texas 78621
>> USA
>>
>>
>>
>> On May 27, 2017, at 7:46 AM, Paul Ricco via Fot <fot at autox.team.net>
>> wrote:
>>
>> PJ,
>>
>> Yes on a suggestion.  We have set up several of these over the years.
>> Assuming that everything else in the brake system is plumbed and working
>> correctly, what you have going on with the balance bar is an indication
>> that you do not have the right size master cylinder bores for the car.  One
>> of the many advantages of the system that your car has, includes being able
>> to select the right size master cylinders for the weight distribution of
>> the car, differences between the front/rear wheel cylinders and the type of
>> brake feel that you want.  Furthermore, the front and rear masters do not
>> have to be the same size (They seldom should be).  The balance bar is meant
>> to be for FINE adjustments.  It sounds to me like it is being used for a
>> much bigger imbalance in the system.  That will not work well.
>>
>> If it is a Tilton pedal assembly, they have a worksheet on their
>> website.  You can fill it out and submit it to their engineering department
>> via email.  In about 3 days, you will get an email back with their
>> recommendation for master cylinders.  They will want to know what type of
>> pedal feel that you want.  They do not charge for this service.  The larger
>> the bores, the more pedal pressure you will have.
>>
>> Pegasus Auto Racing Supply keeps all of the master cylinders in stock and
>> they are very easy to change (provided the pedal assembly is installed
>> correctly).  It is really a very easy problem to address.  I would guess
>> that when the assembly was installed, that someone skipped the step of
>> finding out what size masters are correct for the car.
>>
>> Good Luck,
>>
>> Paul Ricco
>>
>>
>> On May 26, 2017, at 10:28 PM, McKearn McKearn via Fot <fot at autox.team.net>
>> wrote:
>>
>> Hi all.
>>  Trying to get the GT6 back on the road after a long winter in
>> retirement. This car has a racecar style braking system with dual master
>> cylinders and a balance bar for tuning. Last fall I nearly crashed when
>> exiting an off ramp and had NO brakes...
>> After renewing rotors and pads and bleeding the brakes I have discovered
>> that the balance bar is sticking and flipping back and forth . Actually up
>> and down would be more accurate. It seams that the rear brakes require less
>> travel of the master cylinder so the front master cylinder moves much more.
>> This is causing the balance bar to achieve quite alot of angularity. As it
>> moves in and out it sometimes flips up or down and sometimes it actually
>> sticks and refuses to push the left (front) master cylinder in. This seams
>> strange to me as this has worked fine for several years.Any suggestions??
>>                 Thanks.  P.J.
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