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MG Midget and Sprite Technical - Clutch Master size - 1275cc engined cars

Is the clutch master cylinder size on the 1275cc engine cars 11/16" diameter?


Daniel Stapleton

3/4 iirc
Brake drum cars are 7/8
Onno K

Are you sure? CLUTCH Master - it is less than 3/4 so must be less than 7/8. If it isn't 11/16 might it be 0.700"?
Daniel Stapleton

It has always been accepted that
Drums 7/8
Discs 3/4

A member who owns his own machine shop looked in one of his reference books and said it should, as you say, be 0.7 so that is what I now use on my Sebring rep.

Alan Anstead

Thanks Alan. The reason I ask is that I'm going to replace the standard master with a non-standard master. However, while I've got used to the feel of the clutch with the Burton co-ax I have the option when I change the master to have a softer longer travel pedal, like it was originally, by varying from the orignal master size, but needed to be certain what that original size was.
Daniel Stapleton

"It has always been accepted that
Drums 7/8
Discs 3/4"

Clutch or brake?
Dave O'Neill 2

At the change to disk brakes the clutch slave also changed.
I think it was easier to bore both sides of the combined MC the same (no chance of FU's)
Onno K

Daniel - I found an old separate clutch master from a 1275. Couldn't get the piston out but the end of the bore measured to .698 repeatedly. So it seems that 0.7 is more correct than 11/16". Could it be the piston is 11/16 and the bore 0.7 to give running clearance which allows the seal to do its job? (bit like pistons, rings and bores).
David Smith

Definitely 0.7", 3/4 is the brake if discs, 7/8 for drums.
Paul Walbran

Looking back at Onno's post now that it's morning, the reason for the conflicting posts is clear:
1275 has 0.7 master and 1" slave
1098 has 3/4 master and 7/8 slave
Hardly suprising, they were different clutches after all!
Paul Walbran

I use a 3/4 master and a 1" slave on my 1275 frog. It used to have a 7/8" slave but the 1" slave makes for a more relaxing pedal. The difference from 0.7 to 0.75 is fairly small. It also meant the clutch movement was slightly less with therefore reduced risk of clutch overthrow.
Bob Beaumont

An afterthought (actually an after-question) what is the Clutch master and slave size for 1500xx engines#d cars? Is the master the same size but of slightly different internal design?
Daniel Stapleton

And, of course, you will need one of these (see pic)

Alan Anstead

One you prepared earlier ????
Nice to have met at the bolney stage on thursday

rgds tony boyle
a boyle

You'll have to pay Kent a visit on a nice day.
There are a few cars fitted with them now.
Alan Anstead

This thread was discussed between 16/05/2016 and 27/06/2016

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