Brembo RCS 19 and Fren Tubo Brake Line Upgrades

JHTmcrider · Apr 1, 2022

Getting ready to swap out the OEM Brembo master cylinder with the Brembo RCS 19 unit from Motomillion. Also on the schedule are the carbon lines with ABS from Fren Tubo.

Any advice on the bleeding procedures? I picked up a Stahlbus bleeder to help, but was wondering if I'll have any issues? Saw some vid on YouTube about leaving the bike in the "on" position?

Thanks in advance.

RickD996 · Apr 1, 2022

Have you bled brakes before? If you have, it's the same procedure, fairly straightforward.

JHTmcrider · Apr 1, 2022

^ Yea, I haven't bled the V4's brakes but my 1199 brakes years ago. I plan on using the Motul fluid:

JHTmcrider · Apr 1, 2022

Mattysals · Apr 1, 2022

You’re aware the 19 is not the “ideal” size correct?

Mattysals · Apr 1, 2022

For new lines, it makes it a bit easier to reverse bleed.

TomFoolery · Apr 2, 2022

Mattysals said:
You’re aware the 19 is not the “ideal” size correct?

Say more....

Shazaam! · Apr 2, 2022

TomFoolery said:
Say more....

When you change the brake master piston diameter from the stock 16 mm to 19 mm you change the ratio of the areas of the master cylinder to the caliper pistons. This changes the lever feel modulation characteristics from Ducati's normally soft to a poor wooden feel. The Brembo RCS17 pump gives a better feel when used with the M4 30 calipers.

BP PanigaleV4S · Apr 2, 2022

Back when I was toying with the idea of getting a RCS master and more race inspired buttons I read up on the different sizes. I came across a useful post on ducati.ms a while back.

https://www.ducati.ms/threads/brembo-stylema-17rcs-or-19rcs.738140/post-7165157

When you design a hydraulic system it's important to have good feedback from the lever as to how much lever force to apply to achieve a desired braking rate. Having good feel, sensitivity and control is the major factor influencing braking quality.

The main factor in designing good braking modulation characteristics is the ratio of the total area of the caliper pistons to the area of the master cylinder.

The Streetfighter V4S calipers have a total piston area of 5,655 sq. mm, and has a 16 mm master cylinder area of 201 sq. mm. This gives a hydraulic ratio of 5,655/201 = 28.1.

The Brembo 17RCS brake master cylinder has an area of 227 sq. mm. Used with the Stylema M4.30b calipers, you get an hydraulic ratio of 5,655/227 = 24.91.

The general design rule-of-thumb for TWIN rotor brake systems is as follows:

30:1 - soft feel
27:1 - sweet spot for design
23:1 - firm feel
20:1 - wooden feel (poor modulation)

Compare with the alternative: the Brembo 19RCS brake master cylinder has an area of 283.5 sq. mm. Used with the Stylema M4.30b calipers you get an hydraulic ratio of 5,655/283.5 = 19.9.

Jolly Roger V4 · Apr 2, 2022

The OEM is fine anyway for track days with proper pads. And yes I have heard the 19 isn't the one to go with. 17 is the winner.

Steven31371 · Apr 2, 2022

bp_SFV4 said:
Back when I was toying with the idea of getting a RCS master and more race inspired buttons I read up on the different sizes. I came across a useful post on ducati.ms a while back.

https://www.ducati.ms/threads/brembo-stylema-17rcs-or-19rcs.738140/post-7165157

that’s good ...., thanks for posting it.

Jolly Roger V4 · Apr 2, 2022

Ding dongs working from Motorsports Exotica at a Fast track riders event tried to sell me the RCS19. They said oh, are you having brake fade on hard braking? If so
the RCS19 will solve that. I said oh, isn't fade either from fluid boiling in the lines, or pad fade from high temps on the pad above the pads usable working range?
Jaws dropped and complete idiotic silence. Anything for a dollar I guess.

Steven31371 · Apr 2, 2022

I have the RCS 17 Corsa Corta using the stock Stylema calipers…feels great with that setup, I like a bit firmer brake lever feel though.

I’m putting the Brembro GP4-MS calipers on though, we’ll see how the 17RCS feels with those.

Mattysals · Apr 2, 2022

TomFoolery said:
Say more....

The stylema has 30mm pistons inside the calipers. A 19mm master cylinder is going to push a lot of fluid and the lever is going to be very firm. It’s still usable, and some people prefer it. I’ve used a 19 as well but switched back to a 17 after. Lever was way to sensitive with the 19 for me.

Mattysals · Apr 2, 2022

Jolly Roger V4 said:
Ding dongs working from Motorsports Exotica at a Fast track riders event tried to sell me the RCS19. They said oh, are you having brake fade on hard braking? If so
the RCS19 will solve that. I said oh, isn't fade either from fluid boiling in the lines, or pad fade from high temps on the pad above the pads usable working range?
Jaws dropped and complete idiotic silence. Anything for a dollar I guess.

You can use a 19, it’s not “wrong”. It’s just preference.

RODOLFO · Apr 2, 2022

I think 19 V4 had different calipers than 21 bikes

or are they the same?

I have the 19 RCS, on my 19 V4S and feels great, not harsh or wooden

TomFoolery · Apr 2, 2022

Good info @Shazaam! @bp_SFV4

There's so much to lever feel though including rotors themselves and pad compound. The brake master is one of 3 big parts to lever feel.

I generally find the bigger masters are they are easier to bleed. One of my bikes runs a 15mm and it's a gigantic pita to get any pressure in the system especially when bleeding a new line or caliper (even reverse bleeding).

andyb · Apr 2, 2022

Steven31371 said:
I have the RCS 17 Corsa Corta using the stock Stylema calipers…feels great with that setup, I like a bit firmer brake lever feel though.

I’m putting the Brembro GP4-MS calipers on though, we’ll see how the 17RCS feels with those.

which will totally fubar the ABS!

BP PanigaleV4S · Apr 2, 2022

Jolly Roger V4 said:
The OEM is fine anyway for track days with proper pads. And yes I have heard the 19 isn't the one to go with. 17 is the winner.

What pads would you recommend with an otherwise OEM setup?

Steven31371 · Apr 2, 2022

andyb said:
which will totally fubar the ABS!

you think?

I wouldn’t think the GP4-MS would be THAT big of a difference to the ABS

Lots of guys running them

Brembo RCS 19 and Fren Tubo Brake Line Upgrades

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