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Thread: Clutch Master Cylinder

  1. #1
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    Clutch Master Cylinder

    What size are people using who have converted to hydraulics.
    I have a .625 but seem to have too much travel at the pedal end to get a clutch. The only way I can get one is by having the pedal over centre.
    It's all bled through and adjusted so would a .75 sort it out?

    One step forward and 2 back it seems at the mo 😡

  2. #2
    ***Euro-Nova Supporter*** Spacenut's Avatar
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    0.625" is about the smallest bore size you can get. And if your slave cylinder bore is significantly larger then yes, I would say that is a possible reason for the clutch not disengaging. If you can get a smaller bore slave cylinder or a larger bore master then I would agree this would change the pedal ratio and increase the clutch lever movement.

    Don't worry, it's all part of the learning process - it's taken me 20 years (6 of which were on the road) to figure out that my handbrake leverage ratio was too small, so I couldn't get the handbrake to work efficiently - 11 clicks and it would only just hold, reduce the pad clearance and it would bind all over the place. That's the fun of mixing and (mis)matching parts!

    Lauren
    only Pythagoras can save me now!

  3. #3
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    Thanks Lauren
    I think increasing the master cylinder bore may make the clutch slightly heavier to push but that is a small price to pay .

  4. #4
    ***Euro-Nova Supporter*** Spacenut's Avatar
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    Agreed. And for reference I am using twin 0.625" master cylinders for my front and rear brake circuits, so I have to push both in parallel - it's not that bad.
    only Pythagoras can save me now!

  5. #5
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    Hi Mark,

    Not sure which pedals you got, but mine came with two .7 cylinders and one .625 and my understanding is that the .625 is for the front brakes and the two .7 are for rear and clutch?

    Dirk

  6. #6
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    Quote Originally Posted by Dirk View Post
    Hi Mark,

    Not sure which pedals you got, but mine came with two .7 cylinders and one .625 and my understanding is that the .625 is for the front brakes and the two .7 are for rear and clutch?

    Dirk
    Bought the compubrake kit which is probably the same.
    That does make me think, however its a universal kit and they do not know which slave you would actually be using so it is all down to the master/ slave ratio.

  7. #7
    This is the response from Compubrake I had when I queried the set-up on my scooby nova last year

    "Good day DavidRight what we recommend is the following
    0.625 front
    0.7 rear
    0.7 clutch my friend

    Also please find set up guide enclosed

    Kind regards,

    Klint
    "








  8. #8
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    Think me needs to examine the cylinders again then.
    And I had just got a great brake pedal !!

  9. #9
    ***Euro-Nova Supporter*** Spacenut's Avatar
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    Interesting - so the brake bias is due to the different master cylinder bores... so for an equal pedal force applied to each one, the 0.625" will apply more brake pressure than the 0.7", effectively biasing the braking effort to the front wheels. Very clever.

    I assume that this approach is used because brake balance bars are not permitted for BIVA?
    only Pythagoras can save me now!

  10. #10
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    Quote Originally Posted by Spacenut View Post
    Interesting - so the brake bias is due to the different master cylinder bores... so for an equal pedal force applied to each one, the 0.625" will apply more brake pressure than the 0.7", effectively biasing the braking effort to the front wheels. Very clever.

    I assume that this approach is used because brake balance bars are not permitted for BIVA?
    They still come with a balance bar, and I'm not sure that they are not permitted just not happy with them being left adjustable i.e whilst you are driving. I think in the latest's CBS catalogue they say you have to stop them being adjustable once set and have some sticker on them, Ill see if I can dig it out and scan it tomorrow.

    Dirk

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