Clutch master cylinder for rear brake

Discussion in 'Wheels' started by Haliotian, Jul 21, 2012.

  1. Haliotian

    Haliotian Member

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    Hello

    I was thinking of using a clutch master cylinder for the rear brake on my
    Road King. I require a rear hand brake due to the fact that I haven't any use of my legs. I have examined the kits for rebuilding both brake and clutch cylinders and these are very similar in both size and construction. The only noticeable difference is that there appears to be a difference in construction which looks like it would result in a different leverage rate. Any and all comments would be appreciated. Thanks
     
  2. Breeze3at

    Breeze3at Well-Known Member

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    Welcome to the forum. What little I know, is that H.D. hyd. clutch master cylinders are usually 11/16" piston, the same as dual disc front brakes. I don't know the usual rear brake piston size offhand, but you should find out if they are the same. Single disc front cylinders are usually 9/16" or 5/8". A larger piston moves more fluid for 2 calipers, and requires more lever pressure to generate the same psi in the line (I think I just confused myself on the pressure statement).
     
    Last edited: Jul 21, 2012
  3. Haliotian

    Haliotian Member

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    Thanks for the reply breeze. I have been thinking about the same issue that you mentioned. With the larger cylinder, theoretically, it should move more fluid with less effort and the reverse for the smaller cylinder(9/16). I have seen the clutch cylinders listed as 11/16 and some of the Sportsters at 9/16. I was thinking of using a 11/16 until I put a rotor on the sidecar wheel and that should balance things out as far a pressure is concerned due to having a second rotor.
     
  4. fin_676

    fin_676 Experienced Member Staff Member Moderator Contributor

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    Just a thought many years ago moto guzzi developed a system that linked front and back brakes together giving 70% to the front and 30% to the rear allowing good balance of braking with no rear wheel lockup although this system was operated by the foot pedal through a sort of valve block i am sure a similar system working from the hand leaver could produce a good result provided sufficient capacity of the master cylinder

    Brian
     
  5. Haliotian

    Haliotian Member

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    Thanks for the input Fin. I have also thought about the scenario you have mentioned. I live in Nova Scotia and our DMV requires that the braking systems on motorcycles be independent of each other. I have a Revloc auto clutch which leaves both of my hands free to use the levers.
     
  6. fin_676

    fin_676 Experienced Member Staff Member Moderator Contributor

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    It is the same here in the UK a motor vehicle must have 2 independent braking systems however some military vehicles are exempt
    The moto guzzi system worked 1 brake on the front and the rear brake and the hand leaver worked the other front brake

    Brian
     
  7. Breeze3at

    Breeze3at Well-Known Member

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    I'd not heard of the Revlock Auto Clutch before. I just read about it, and it sounds pretty efficient. Keep us us updated on your progress with the brakes and any other special mods you do. I like learning different ways things can be done.