[Mgs] MGB rear brake questions

[PaulHunt73]

The GT originally had the same wheel cylinders as the roadster, changing 
in May 68 for the larger item which can take more braking effort without 
locking up in the wet.  Incidentally the factory V8 used the smaller 
ones, presumably because with the harder springs there was more chance 
of locking up over bumps.  You are unlikely to notice the difference on 
dry tarmac.  Rather than describe them the two types can be seen here 
http://www.mgb-stuff.org.uk/brakecyl.htm#3

The purpose of Speedbleeders is to allow single-handed pedal bleeding of 
hydraulic systems, but they are pretty expensive for what they are and 
the number of times they are used.   They contain a spring-loaded valve 
which is normally bolted down tight, but when bleeding you slacken them 
off so that only the spring is keeping the valve closed.  Then when you 
press on the pedal fluid pressure opens the valve to let air/fluid out, 
and when releasing the pedal they close again to stop air going back 
in.  I've always used EeziBleed.

Regardless of which method you use to get air out I've always found that 
after low pressure bleeding they are spongy and it needs to be done with 
high pressure that does need two people. One presses down on the pedal 
as hard as they can while the other rapidly opens and closes each 
caliper nipple in turn, which always blasts a bit more air out, after 
that they are fine.  The front of the car needs to be a bit higher than 
the rear as well.

PaulH.

On 23/10/2021 18:44, wkilleffer at epbfi.com wrote:
> As far as the type of wheel cylinders, I don't recall that there was a 
> choice as to whether they were for a GT or a roadster. The only choice 
> was either Lockheed brand (maybe) for more $, or an aftermarket for 
> less $. As far as I know, the back plates are original, but I've only 
> owned the car for 20 years. Its engine is not original, so who knows 
> what else could have been swapped.
> Can you shed more light on the whole speed bleeder thing? And how do 
> do pedal pumping bleeding when you're by yourself?
> The fluid is making its way back to the wheel cylinder, so no lines 
> are crimped. But thanks to the poor fitment of the bleeder thing with 
> the tool, I can't tell if the air bubbles are coming through the brake 
> lines or are air being drawn into the bleeder because the fitment 
> isn't good.
> Yes, I did the clutch system a couple or three years ago. It was a bit 
> frustrating, but seems ok now.
>
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