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Rear Brake slave size?


SpitFire6
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Hi,

 I believe there are 3 choices for a slave cylinder on a GT6.

5/8", 5.5/8" & 6/8"?

If I measure the diameter of the exposed piston end, should this be the same as the internal diameter of the piston? The end diameter is way smaller than even the 5/8".

The cylinder is seized solid & will not come out. Suspect it's been seized for many years while on the car.

No info on the body.

Cheers,

Iain.

Slave.JPG

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Hi,

 so 5/8", 5.5/8", 6/8" & 7/8". 
 

I am curious about what I had in the back. Both have been replaced with new. Can't remember. LOL.

I just drilled the plate out on the backside and through to the inside.
Now the wife has gone to work I am heating it in the oven @ 230c. Will drop it in some tap water and bang the cylinder out. If it doesn't come out I will give up on it.

Cheers,

Iain.

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12 minutes ago, Pete Lewis said:

or fit a grease nipple and get the wanner to pump it out 

Pete

Wanner? unnaturally pale, esp from sickness, grief, etc?

I can't hydraulically remove it as It has a 10mm hole in the backside now.

Just dunked it. No joy.

will give it 60 mins in the oven and then going to dunk it in phosphoric acid while holding breath. Leave it for 24 hours.

Will see if it dissolves more of the alloy.

Cheers,

Iain.

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Hi Doug,

The only GT6 part of the car is the Logbook. Its a "Triggers Brush".

It has the skinny manual rear shoes. It was a single system but now tandem after the rear flexible leaked & I lost brakes. That's when I found that the cylinder was seized despite it going through many MOT's. Seems that the Quaife for one reason or another caused a pass every time.
 

The car is in lockdown at the moment hundreds of miles away so I can't check its partner. Nothing else better to do I thought I would check this one.

It's sitting in acid at the moment fizzing away. Hopefully, something is left to measure tomorrow!

Thanks,

Iain.

 

 

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44 minutes ago, thescrapman said:

The bigger the rear cylinder the more pressure is available to move the shoes for the same pedal pressure, but the longer the pedal travel.

so I think th article has it back to front.

Is it not more force not pressure or in this case same same?

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41 minutes ago, SpitFire6 said:

Is it not more force not pressure or in this case same same?

force=pressure x area. 

So for a given pedal pressure, a larger piston will apply a larger force on the shoes.

too much rear braking is best avoided.....

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Hi,

 including a spitfire one, there is now four available as the fifth is not available.

 so 5/8", 5.5/8", 5.6/8", 6/8" & 7/8".

I had half the smallest & now probably the smallest available. No wonder the disks & tyres do not last long. LOL.

Bigger might give more feel. My front are a knats less area than OEM GT6.

Cheers,

Iain.

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  • 1 year later...

I've just replaced the daughters Mk2 Spit rear slaves after checking the manuals etc with the correct 0.75in NOS Girlock originals, the seized ones I had fitted 20years ago were Vitesse 0.7in units as I had them as spares, If I remember correctly my research showed Mk1/2 were o.75, later Mk3 & 4 went smaller at 0.625 and 1500's back to bigger to 0.7in.

So now i've rebuilt the Girlock 0.7's as there was no bore damage cleaned with meths and a dremmel round softish scour sponge type bush a couple of times up the bore, bores perfect, piston no rust then new seals and boots. Prefer tp keep the Girlock's rather than unknown aftermarket?

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