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I just upgraded my brake system, changed to Brembo 19RCS Corsa Corta Master Cylinder, HEL braided lines, and Rizoma "Next" Fluid Tank CT127A. New brake pads are also replaced on the upgrade. Now it's only been 400km since my upgrade. However the fluid tank oil level already dropped to almost half (between the Max and Min line). I am thinking that the Rizoma fluid tank is not big enough, so that the oil level dropped significantly. Should I be worried about the situation? Or just add the oil when it reaches the minimum level?

I read about the Corsa Corta's user manual regarding the lever ratio adjustment and I am a little bit confused. It said as below,

"the lever ratio adjustment (Ratio Click System) that permits to fix the lever ratio on two

possible settings: 18mm for the maximum brake power control, 20mm for maximum

readiness of the brake system."

https://www.google.com/url?sa=t&rct...10c74010.pdf&usg=AOvVaw1JY2jAaT5XgZwUeM-pTtBN

May I know which setting 18mm or 20mm is better for street riding? I don't want the brakes to be too aggressive.

Thanks in advance.

Cheers.



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Did you bleed the brakes after upgrading? The oil level should not go down and in any case if it goes down it should be very little.
For road use you must set it to 20. This is the lever stroke, 18 becomes shorter and more aggressive.
 

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Discussion Starter · #3 ·
Did you bleed the brakes after upgrading? The oil level should not go down and in any case if it goes down it should be very little.
For road use you must set it to 20. This is the lever stroke, 18 becomes shorter and more aggressive.
Thanks for the reply.

The garage did the brake upgrade for me, so it should have no problem about bleeding the brakes, and it feels solid.

I just set it to 18 now. The brake force feels more gradual.

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The reservoir is not too small. All the fluid is in the lines, only a small amount of fluid in the reservoir is required. And once the system is bled properly and the lever action is hard (not spongy), the level should not drop. Fill it back to full, and it should stay there, as you say the brake action feels good.
 

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Did I read correctly that you put in new pads, too? If so, totally normal for your fluid level to drop a bit. New pads will bed in and will lose a bit of material in the process, forcing the caliper pistons to push out a bit farther to account for the wear, and that drops your fluid level. But once that initial bedding in happens, the fluid level should not drop further (or, to be more accurate, it will only change as further wear occurs, but that will happen much slower now.)
 

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The 18mm is smaller hole so it pushes the fluid through with more pressure giving you that initial hard bite at first lever pull and more power with less lever pull distance traveled. 20mm gives you a bit softer feel and more control through the pull.

I like the 18mm as I am tuned to Suzuki Brake fade issues when on track so I like the stiffest feel I can get so over the course of a race I don't pull the lever to the clip on and have no brakes as I get with stock Suzuki Master Cylinders. I bought a set of the quick connect brake lines for my race GSXR so I can swap between my Brembo and Stock depending on the class.

GSXS was the worst I have ever seen for Suzuki Master Cylinders with 1.5 inches of lever pull before pressure on the pads. On track I wouldn't trust it as my stock GSXR unit I can use 1 finger at start of race 2 laps in I have to use 3 fingers to make room as the lever is closer, bu laps 7-8 I have to use all fingers on the lever so I can still get pressure as the lever almost comes back to the bar. This is even with bleeding the brakes at lunch on race day.
 

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Are you guys using braided lines or stock?
I'm also using the Brembo 19 RCS. I don't do any racing but have done 2 track days with the gsxs, one really HOT one in Atlanta first weekend in August but I never had the kind of brake fade you're describing. Of course, I'm not at racing pace either but still hit the brakes pretty hard in hot temperatures. However, I do have HEL braided lines.
I recently replaced all the brake fluid after finding some "crusty" stuff in the bottom of my reservoir. After bleeding the brakes, it seems just fine, just like it was before I replaced it.
 

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I have always been on braided lines with my race bikes since 2001 and every one has had this issue. My 03 GSXR 600, K1 GSXR 1000, K6 GSXR 1k, and my current K9 GSXR 1000. Now when I have my brembo MC on my K9 no issues. Soon as I move to the Stock MC issue as above. My K9 Stock MC (yes it was replaced under the Recall) has about 1/2" of lever travel before pressure at the pads. End up staying on the Stock on race day since no time between races to swap whole brake system.

My GSXS had 1.5" of travel at the lever before pressure that is why I just went straight to Brembo MC and Stainless lines (I had Spiegler build a set from my stock ones). Now on the street I don't use the brakes often enough to heat them up and get fade.

If you had the Brembo MC on during your track day that is why you didn't get any fade. The issue is the internals of the Stock MC. I think they use Nissin MC. I kept researching to find a way to take out the slack in the stock MC by preloading the MC Plunger but no luck. Why I had Speigler make a special set of the Quick connects so I can swap just the MC's without having to -rebleed the lines.
 

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The 18mm is smaller hole so it pushes the fluid through with more pressure giving you that initial hard bite at first lever pull and more power with less lever pull distance traveled. 20mm gives you a bit softer feel and more control through the pull.

I like the 18mm as I am tuned to Suzuki Brake fade issues when on track so I like the stiffest feel I can get so over the course of a race I don't pull the lever to the clip on and have no brakes as I get with stock Suzuki Master Cylinders. I bought a set of the quick connect brake lines for my race GSXR so I can swap between my Brembo and Stock depending on the class.

GSXS was the worst I have ever seen for Suzuki Master Cylinders with 1.5 inches of lever pull before pressure on the pads. On track I wouldn't trust it as my stock GSXR unit I can use 1 finger at start of race 2 laps in I have to use 3 fingers to make room as the lever is closer, bu laps 7-8 I have to use all fingers on the lever so I can still get pressure as the lever almost comes back to the bar. This is even with bleeding the brakes at lunch on race day.
Huh? The adjuster has no effect on any hole. The 18mm setting is a shorter fulcrum setting than the 20mm option (for the lever), increasing mechanical leverage on the piston (at the cost of grater lever travel).
 

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Ok so I misunderstood how the ratios were obtained by reading Brembo's descriptions. The way I understood was the difference were achieved by fluid dynamics no leverage, but seems that is not the case.

Found on Ducati forum said:
The first thing to consider is that moving from a 18mm to a 19mm master cylinder will change the hydraulic ratio (caliper piston area/master cylinder area) from 25.4 to 22.8. A ratio of 27 is considered desirable, 23 is considered to be a firm lever, and a ratio of 20 is considered to be a wooden lever with little feel and hard to modulate.

Second, the piston fulcrum distance modifies the above change. For a given applied force, the longer the fulcrum, the better the modulation but the lower the force on the caliper pistons. The shorter the fulcrum, the greater the force applied to the caliper pistons but with worse modulation characteristics.

So you need to pull the 20mm lever with 11% more force to stop at the same rate as the 18mm lever.

The 18mm lever needs a longer lever pull than the 20mm, but 11% less lever force is needed to stop at the same rate as the 20mm. The 19x18 lever provides a little more feel, and a lighter pull on the lever is required.

Consequently the 18mm has better modulation characteristics, i. e. more feel; Brembo says this is better for the track.
The 20mm provides a quicker braking response; Brembo says this is better for the street. The 19x20 model gives the stiffest brake lever.

So when a rider says he can feel the difference this is what they are sensing
 
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