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.
>>>>> _______________________________________________
>>>>> fot at autox.team.net
>>>>>
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>>>>>
>>>>
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