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Master cylinders... educate me

Discussion in 'Tech' started by crazymofo, Dec 5, 2010.

  1. crazymofo

    crazymofo Then i was like...Braaap!

    im looking to upgrade my matercylinder as my next purchase for my k6 gsxr 1000 race bike.

    im currently running the standard 19mm?? K6 GSXR 1000 master cylinder, with 06 R1 calipers, linked with a full 2 line kit HEL braided lines, and fitted with galfer race pads (has white ceramic backing), clamping standard gsxr disc's

    the stopping performance is great, but as always, wanting more.

    im finding that while im enjoying a firm lever feel, im having to use lots of force to get the brakes to work effectively, where as with the standard gixxer calipers im hate the spongey feeling at the lever, but enjoy the lesser effort at the lever to make it all happen.

    so my questions are, what master cylinder would you reccomend? 19x18, 19x20, 19??

    whats the differences in feel between the cast and billet? (obviously billet wont flex as much etc)

    should i stick with brembo? or can i run a different brand?

    what about an R1/R6 brembo master cylinder? would it be a better item then the OEM gsxr one?

    my intention is to run the standard gsxr calipers once more, to comply with local superstock rules.

    thanks for your inputs in advance.

    cheers.joe.
     
  2. auz_gsxr

    auz_gsxr Well-Known Member

    Brembo 19x18 for better feel and less force :)
     
  3. craigcoble2000

    craigcoble2000 Well-Known Member

    I put a R6 MC on my bike and have not had any issues. I also put speedbleeders on MC and brake calipers and that seemed to make it easier too.
     
  4. middleton1978

    middleton1978 Well-Known Member

    Are you selling the calipers and spacers>>??
     
  5. SV650R

    SV650R GSXR ASSASSIN

    With the R1/R6 4 piston Sumitomo calipers, my recomendation would be a R1/R6 Brembo 16mm master...

    If you plan on going with stock GSXR Tokico calipers, a Brembo RCS19... This way you can shift from 18-20 mm pivot to plunger distance...

    I have a used Brembo 19X20 I am considering selling to purchase a Brembo RCS19...

    Another thing... Have you try Vesrah RJL brake pads?

    Luis
     
    Last edited: Dec 10, 2010
  6. auz_gsxr

    auz_gsxr Well-Known Member

    Are the stock brembo MC's 16x18 or 19x16?
     
  7. SV650R

    SV650R GSXR ASSASSIN

    Yamaha Brembo's Master Cylinders are 16x18... That is 16mm bore and piston, 18mm pivot to plunger...

    19x18 and 19x20 are both 19mm bore and piston, and either 18mm or 20mm pivot to plunger...

    Luis
     
  8. auz_gsxr

    auz_gsxr Well-Known Member

    so why not use a 19x18 on the yamaha monoblocks?
     
  9. SV650R

    SV650R GSXR ASSASSIN

    You can... You can use which ever master you want to use... If you understand how each master cylinder will affect your braking...

    Bigger is not always better...

    Unfortunately for me, I did my homework on this, and now I want to experiment different possibilities...

    The R1/R6 Calipers seem to work best with a 16mm master cylinder...

    To figure out hydraulic multiplication, you need to get the area of each piston on 1 side of each caliper...

    For the Yamaha R1/R6 it is 4-27mm and 4-30mm pistons... Now, we only need one side per caliper... 2-27mm and 2-30mm...

    The area of 1-27mm piston is 572.5553 mm square
    The area of 1-30mm piston is 706.8583 mm square

    The area of 2-27mm pistons is 1145.1106 mm square
    The area of 2-30mm pistons is 1413.7166 mm square

    Ad them together 2558.8272 mm square

    A 16mm master cylinder is 201.0619 mm square
    A 19mm master cylinder is 283.5287 mm square

    2558.8272 / (16mm) 201.0619 = 12.7266 hydraulic multiplication force
    2558.8272 / (19mm) 283.5287 = 9.0249 hydraulic multiplication force

    This means for each 1 PSI the plunger is pressing on the 16mm piston, will multiply it by 12.7266... And for each 1 PSI the plunger is pressing on the 19mm piston, will multiply it by 9.0249...

    What is the trade off?

    16mm master cylinder = More lever movement to push the same amount of brake fluid... More braking force with samer hand pressure effort...

    19mm master cylinder = Less lever movement to push the same amount of brake fluid... Less braking force with same hand pressure effort...

    To me... a 16mm master cylinder offers more control...

    Then again you have to test every theory... :D Luis
     
    mike-guy likes this.
  10. Boman Forklift

    Boman Forklift Well-Known Member

    SV650R, Thanks for explaining that and showing the math. Even as I followed your example, I thought it was going to show the bigger piston exerted more force per pressure of hand movement. To me that seemed logical in my mind, so thanks again.
     
  11. auz_gsxr

    auz_gsxr Well-Known Member

    Agreed but then you need a lot of lever movement... another option is a 19x16 too :)
     
  12. KrooklynSV

    KrooklynSV Usual Suspect

    :stupid: That's a much better idea than trying to run a 16x18 with a set of Yamaha calipers.

    Also, although Yamaha's OEM Brembo might be 16x18, it's not a "true" radial m/c, so that comparison is not a good one.
     
    Last edited: Dec 12, 2010
  13. crazymofo

    crazymofo Then i was like...Braaap!


    unfortunatley no, im keeping them for my k4 gsxr 1000 roadbike



    sv650r....

    brilliant info thank you so much for explaining it all in such depth.

    im unsure of how you were able to determin the piston area, care to share?

    ive opted for a ducati 1198s brembo master (19x18 from what i understand) hope fully that will work well with the stock calipers gixxer calipers???.

    thanks very for your help :beer:

    cheers.joe.
     
    Last edited: Dec 12, 2010
  14. SV650R

    SV650R GSXR ASSASSIN

  15. crazymofo

    crazymofo Then i was like...Braaap!

    brilliant thanks very much luis.

    cheers.joe.
     
  16. 2001chromo

    2001chromo Well-Known Member

    I'm curious why you think this master cylinder is not a radial?
     
  17. KrooklynSV

    KrooklynSV Usual Suspect

    The OEM Brembos on a Yamaha (at least last I looked) are not perpendicular to the bar, they're at a ~60 degree angle. Close, but not a "true" radial.


    [​IMG]
     
  18. -M-

    -M- Member

    SV650R... I'm no expert, but doesn't your example fail to take into account the size of the oil gallery that channels the oil being compressed by the piston?

    Assuming the gallery is the same diameter (which I believe but cannot prove) on all Brembo master cylinders regardless of piston size, the bigger piston would create more pressure. I believe this to be true otherwise the master cylinder grading system would not be relative. It also makes sense to me because Brembo recommends (aftermarket) 19mm pistons for dual caliper systems and 16mm pistons for single caliper systems.

    Assuming this is true, the largest piston with the smallest pivot length would provide the greatest amount of potential pressure.

    Based on personal experience, I would suggest it is true. I use a 19x16 and the breaking ability is greater than my previous 19x18, which in turn was better than my 19x20.

    Although all 19mm masters obviously share the same piston size, the the closer the pivot is to the plunger, the more leverage you can exert on the piston. It's the same argument as comparing long and short levers... Racers generally prefer longer levers as it allows them more leverage.
     
  19. SV650R

    SV650R GSXR ASSASSIN


    Those are 100% radial... It is just a different design due to the possition of the pivot point...

    Luis





    The Bore and the Piston are almost the same size... YES, the piston needs to be able to slide in the bore... But, there is a seal that makes up the diference... Aftermarket master cylinders have tighter tolerances... That is wht you have better feel...

    Master cylinders are NOT match for power output... Master cylinders are match for the amount of fluid the calipers require to brake...

    16mm by 18mm pivot to plunger are usually the standar for single calipers, or 2 calipers with 2 pistons each (4 pistons total)...

    19mm by 18mm pivot to plunger are usually the standar for 2 calipers with 4 pistons each (8 pistons total)...

    19mm by 20mm pivot to plunger are usually the standar for 2 calipers with 6 pistons each (12 pistons total)...

    Yamaha R1/R6 4 piston calipers have smaller pistons than GSXR 4 piston Calipers... Because of this, they can use 16x18 master cylinders...


    Pivot to plunger dimension is another common misconception...

    You are right!!! The shorter the pivot to plunger dimension the more pressure you can attain due to simple mechanical leverage... However, it also will move less fluid, with the same stroke lenght of the lever...

    How much fluid do you calipers need?

    Luis
     
    Last edited: Dec 13, 2010
    MELK-MAN likes this.
  20. MELK-MAN

    MELK-MAN The Dude abides...

    It's not a billet piece if that is what you mean, but the stock r6 mc works pretty good imo (on an r6).



    I didn't know the definition of radial required it to be perpendicular to the bar?? The pivot of the lever is the same, and although the angle the plunger push is at is slightly different, that is some very fuzzy math that im not sure could make it better or worse. Im sure the engineers at Yamaha/Brembo have a reason for that angle as it appears it would not be difficult to alter the angle.. In fact, the angle of the R6 mc is at, is directly in line with the travel of the lever.. :)
     
    Last edited: Dec 13, 2010

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