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Master Cylinder Query


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#1 peasoup39

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Posted 14 April 2022 - 12:20 PM

Bought a replacement dual master brake cylinder for my 1978 mini clubvman estate. Bought it  about a year ago and its a GMC227Z with yellow cap and M12 and M10 ports . Its now fitted and i have altered the operation from diagonal to front and rear split

However the brake pedle is now about 2" higher than the clutch. Can anyone thow some light on why this should be. Have i bought the wrong one?



#2 Ethel

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Posted 14 April 2022 - 01:10 PM

I'm not aware of there being a different version. Reserve pedal travel is the concern, but it should leave you more reserve  because of the larger bore. You could look at swapping the push rods over, but the retainer plate might be a different diameter too.



#3 ac427

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Posted 14 April 2022 - 01:12 PM

Bought a replacement dual master brake cylinder for my 1978 mini clubvman estate. Bought it  about a year ago and its a GMC227Z with yellow cap and M12 and M10 ports . Its now fitted and i have altered the operation from diagonal to front and rear split

However the brake pedle is now about 2" higher than the clutch. Can anyone thow some light on why this should be. Have i bought the wrong one?

 

Do you still have the old master cylinder to compare the new one with?



#4 peasoup39

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Posted 14 April 2022 - 03:05 PM

 yes i have the old one but it has a broken clevis hence the need to change. New unit is already fitted so it is a problem to compare. Strange thing is when fitting  the clevis pin it was perfectly in line with the brake pedla hole and the pushrod and also the fiting of the split pin was easy as the pin was in the same position as when i took it out.



#5 Ethel

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Posted 14 April 2022 - 04:41 PM

The brake pedal was higher on all the dual circuit Mins I've had, deliberately for the reserve pedal travel, but not by 2 inches. To sort it you'd either have to shorten the pushrod or raise the cylinder.



#6 peasoup39

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Posted 14 April 2022 - 06:05 PM

I have had a proper measure rather rhan an exagerated guessa made worse by the  angle i was looking at it. With clutch up to max height and brake pedal on full spring return the difference is now about 1/2 to 3/4". From what you are saying this is normal. I also checked the stroke and have full brake travel down to the floor so it seems i may be OL



#7 Spider

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Posted 14 April 2022 - 06:18 PM

Just check here that as fitted you, the pedal isn't contacting the inner of the bulkhead here;-

 

iycD4YU.jpg

 

Otherwise it'll be fine.

If you find the pedal sits too high to be comfortable to use, you can shim up the mounting base of the Master Cylinder to lower the pedal.

 



#8 peasoup39

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Posted 14 April 2022 - 06:52 PM

Next job is to bleed all the brakes. if i get good pedle and effective brakes i will leave as is unless as you say its not comfartable to get your foot up high to apply.

Thanks for all your assistance.

Job getting exciting now as i am starting to put everything back on. Engine in next week and then off to paint. Alrady starting to scratch my head at where some of the bits go as it was a totaal strip down over a year ago. However with the knowledge of the forum and everyone's willingness to help i will get there in the end






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