It seems to be the season for brake work so I'll add another question on the
subject.
My '57 MGA has the stock drum brakes on the rear but the DPO installed early
MGB disc brakes on the front. The brakes work well but brake pedal travel is
excessive (pedal travels over half-way before it's solid). Pedal travel is
normal/short after one or more pumps of the pedal. The DPO says he just got
used to always giving the pedal a pump to bring it up.
Since there was over 10 years of very little use and one rear wheel cylinder
was leaking a little, I overhauled the rear wheel cylinders, brake master
cylinder, and clutch master cylinder. All appeared to be in good shape
except for deteriorating rubber. After getting everything back together and
bleeding the system the pedal travel is now just as excessive as before. I
have the rear drums adjusted correctly (one click shy of lock-up), the front
pads look good, I've bled the system over again, and there are no leaks or
loss of brake fluid, but pedal travel is still over half-way to the floor
before it's solid. After one or two pumps the pedal is solid with short
travel.
Is it possible that the stroke volume of the brake master cylinder is too
small for the volume of the cylinders on the MGB front discs? Is it possible
to bore out the cylinder and get oversized pistons, cups, etc.? I think
later MGA's with stock front disc brakes used the same master cylinder as
early all-drum models. Could there be that much volume difference with the B
brakes? Also, there is a non-return valve in the brake master cylinder which
is supposed to maintain some pressure in the system. If the system maintains
pressure, then volume of the master cylinder shouldn't really
matter...right??? Am I chasing the wrong zebra here?
Any help on this would be appreciated.
Keith Baer
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