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MG Midget and Sprite Technical - Are all clutch slave cylinders created equal?

Hi chaps
About to fit a new clutch slave and have noticed that it is labeled for a 1098, I have a 1275. Can I use it?
T Dafforn

Pretty sure they are different internal diameters. There was certainly a change, I am just not sure when exactly. The different diameter will give a different amount of travel to the pushrod when you press the pedal. The early versions were the larger ones I think, sof you fit to a later car then the clutch won't fully disengage.
Guy W

I think it's the other way round. The 1098 is a smaller diameter, so you get too much travel with a 1275.

I believe the inlet port thread is also a different diameter.
Dave O'Neill2

Quite right! Sorry I got that wrong. I really should have remembered because that is exactly what I did ! - I fitted an earlier slave to my 1275 Sprite and it ruined the clutch because it overthrew. It was actually what encouraged me to fit a Type 9 with a concentric slave.
Guy W

Thanks Chaps..
T Dafforn

Could you not just shorten the rod in the 1098

How does over throwing ruine the clutch...I mean that sincerely...what parts got damaged

Fingers on the diaphram perhaps ???

Intresting thought to play with

Prop and the Blackhole Midget

Shortening the pushrod won't alter how far the piston moves. It just shifts the start and finish positions of the slave piston a little way down the bore.

Overthrowing a clutch is when the release bearing moves too far towards the flywheel. It releases the clutch driven plate but then continues to flex the spring fingers and strains them so they don't return to the same position when the clutch pedal is released. After repeated times this takes the springiness out of the metal and ruins the clutch.
Guy W

Ah...I was thinking fingers...makes scence

I knew that on the not sure why that didnt click when I wrote the question...DOH

Prop and the Blackhole Midget

odd this as I have a 1275 engine with the earlier slave. Its been in there for a over 5 years and i have had no problems with the clutch. I am using the later 1098cc master cylinder which has a smaller bore than the frog one as I also run discs. the clutch pedal has a pin welded to it to stop the pedal moving too far (i think they all have as i have a couple spares which also have the pin. The adjustment on the pushrod is as per factory settings.
Bob Beaumont

I use the earlier slave cylinder on my 1275 to get the longer throw needed with a 7.5 inch clutch. I had a great deal of difficulty getting the clutch to disengage. Longer pushrods worked to some extent but even with these carefully adjusted it was very marginal (and went out of adjustment very quickly). The smaller bore gives a longer throw when mated to the original M/C. I had to obtain an adapter so I could connect the flexible hose as the thread sizes are different.
Chris H (1970 Midget 1275)

1275 clutch is an interesting beastie, if you over-stroke it not only does the diaphragm stress as usual in such cases, but the release ring makes contact with the plate causing it to drag. This leads to the counter-intuitive situation whereby you have to release the pedal a bit to get the clutch to disengage fully.
Paul Walbran

This thread was discussed between 11/06/2013 and 12/06/2013

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