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Brembo 19x18 brake MC not a good choice for the R6?

Discussion in 'Tech' started by duc995, Oct 22, 2018.

  1. duc995

    duc995 Yep…

    After a recommendation from Braketech due to Ferodo CPro pad cost/size availability I just did a caliper swap and now have modern R6 calipers, but i’m finding braking power somewhat inadequate now. I am being told ... a little bit after the fact ... that the R6 calipers use smaller than average diameter pistons and that the 19x18 Brembo was not a good choice in this application. What are the specs on the modern R6 OEM brake MC? What do racers replace their stock mastercylinders with?
     
  2. MELK-MAN

    MELK-MAN The Dude abides...

    I like the OEM brembo master cylinder.. i prefer it's feel. (on an R6 that is.. can't say on other bikes).
    Is your lever too close to your grip? if so, you won't get any leverage (less power). Love the oem master, with the GP Tech folding lever and their remote cable adjuster.
     
  3. duc995

    duc995 Yep…

    Lever is adjusted correctly. I have always used two fingers for braking; may need to use more if I don’t replace the Brembo 19x18 Mk2 now :(
     
    Last edited: Oct 22, 2018
  4. MELK-MAN

    MELK-MAN The Dude abides...

    "adjusted". sorry, shouda clarified a bit more.. . i don't mean distance from the grip (reach to the lever).. I mean if you move the perch to the left on the bar, toward the steering stem, a mathematical phenomenon occurs, giving you more power on the brake's hydraulics
     
  5. duc995

    duc995 Yep…

    Thanks. I understand your point completely. At present there is no room to move the perch to the left - but I get what you are suggesting.
     
  6. SPL170db

    SPL170db Trackday winner

    Well here's Gerloff on his old R6 with a very clearly OEM MC on his Supersport racebike. Pretty sure class rules allow them to swap those out for aftermarket.

    [​IMG]
     
    MELK-MAN likes this.
  7. duc995

    duc995 Yep…

    What spec aftermarket replacement do they use?

    Further searching on this site seems to indicate 16x20 for the stock R6 MC.
     
  8. duc995

    duc995 Yep…

    When I search for a Brembo aftermarket replacement the closest I find is a Brembo 16x18, but it says it is intended for single disc setups.
     
  9. moto316

    moto316 Well-Known Member

    RCS17 should be close enough to OEM. I have the same problem with the M50 calipers on my ZX10, piston size is smaller and suited for a 17mm mc. Running a 19mm almost put me on my head a couple times while trailbraking leant over, very little feel and modulation.
     
  10. Gumby647

    Gumby647 Señor Member

    I've put a few Galespeed 17mm VRC masters on R6's and everyone has liked them. They are available through Graves.
     
  11. stangmx13

    stangmx13 Well-Known Member

    anyone have an accurate measurement of the pivot distance for the stock R6 master? looks to be 19-21mm
     
  12. duc995

    duc995 Yep…

    So using a 19 mm piston mastercylinder gave you too much braking force? I am using a 19x18 and feel that I am lacking power, however, I have never tried the R6 master with the 16 mm piston to compare. I suppose the new-to-me pads could be an unknown quantity as well.
     
  13. SPL170db

    SPL170db Trackday winner

    I've used the R6 calipers on my 1000 before coupled to a 19x18 Brembo MC and Vesrah SRJL17 pads in them. Helluva bite and very strong braking, I wouldn't say that they were TOO much braking but I do tend to prefer my brakes to have good initial bite. I could see it being a little much to deal with in hard trail braking situations where you want a little more modulation I guess.
     
  14. humblepie

    humblepie Well-Known Member

    Both Gerloff and his teammate hated the feel of the aftermarket MC that their team retailed to customers. They both tested the standard OEM mastercylinder and were quite happy, using them for the remainder of their time on 600's.
     
  15. stangmx13

    stangmx13 Well-Known Member

    with a larger master bore, the main issue is not that there is too much braking force. u can just pull the lever softer and get the same amount of braking force. the real issue is that a small change in lever force produces a larger change in braking force. so the larger bore is harder to modulate and provides less "feel".

    if u have a lack of power... maybe less "feel" is taking away some of your confidence, so u don't want to pull the lever harder. but id rather bet that your pads are crappy.
     
    Ra.Ge. Raptor likes this.
  16. Derick

    Derick Well-Known Member

    I ran a 19x18 with SRJL pads and I could flip the bike over. Something isn’t right
     
    track wagon likes this.
  17. duc995

    duc995 Yep…

    Thank you for that info. I’m starting to think it is the pads now.
    Thanks everyone for your contributions.
     
    Last edited: Oct 24, 2018
  18. Derick

    Derick Well-Known Member

    Forgot the stainless steel lines, but figured that was a given
     
  19. Mran556

    Mran556 Well-Known Member

    Does anyone have a chart with master cylinder size vs piston size(pistons in caliper i mean) = what force? I dont know how to do the math but it would clear up alot i think. There has to be an equation for it. Obviously theres different sized pistons in the caliper.. example 2, 28mm. 2, 32mm.
     
  20. jd41

    jd41 Well-Known Member

    Waddup @duc995 !

    MCN had an article on it but I'm unable to find it in their new website. Here's a portion of it that I had saved.

    The basic theory of hydraulic leverage says that because liquids are not compressible, hydraulic brake fluid will transfer the pressure (force)created by the master cylinder directly to all parts of the hydraulic system. And as brake lines are designed to resist this pressure (and braided stainless steel lines are preferred as they are meant to be the most resistant), the force of this pressure can only move the caliper pistons. Plus, being able to use flexible hoses instead of mechanical linkage like cables makes suspension movement much easier to accommodate.

    The hydraulic leverage effect of a brake system results from the ratio of the sizes in the master and slave pistons. If we compare the area of the master cylinder piston’s face to the area of the caliper piston(s’) faces, we get a force ratio that represents this hydraulic leverage. For illustration, let’s say the ratio is 1:10, meaning ten times as much force will be applied to the caliper pistons as the force that’s created by our fingers at the master cylinder. Note also that the movement of the caliper pistons will be the inverse of this ratio, so the caliper piston(s) will move just 1/10th as far as the master cylinder piston moves.

    The formula for area is pi x radius squared

    Using the Brembo’s 15mm master cylinder piston (area: 176.72mm2) with the stock caliper pistons gives a 7.24:1 hydraulic ratio. To determine the overall leverage ratio, we must multiply the hydraulic and mechanical ratios together. We’ll use the stock ratio as a constant, giving the stock Nissin a 10.1:1 overall ratio.

    Comparing mechanical leverage, we find the Brembo’s 18mm pivot gives 50% more leverage than the stock 27mm pivot (27 divided by 18), and its 20mm pivot gives 35% more than the stocker. Multiplying these factors together with the Brembo’s hydraulic ratio of 7.24:1, we find its overall ratios are either 10.86:1 (18mm) or 9.77:1 (20mm) compared to the stock 10.1:1. Using its 18mm pivot, the Brembo will need a little less hand effort to achieve the same power at the calipers and will need slightly more travel to do it. With its 20mm pivot, you’ll need more effort but use less travel.


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    Also: Basic Hydraulic System Theory

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    And:

    Calculator for finding the proper size radial master cylinder.
     

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