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Discussion Starter · #1 · (Edited)
Have heard good things from various friends about upgrading the stock brake lever/master cylinder to a 19mm unit

Wanted to understand if its worth putting down approx $300 on a Brembo RCS 19 and how drastic is the performance upgrade with this. Anyone who has done this switch?

I use my bike mainly at the track and for quick weekend rides.

Thanks a ton. :biggrin:
 

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2016 Kawasaki ZX-10R KRT ABS Edition
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It's all about preference. IMO: you're only going to get faster on your bike, not slower... and the faster you're going the more braking you're going to need to apply without sacrificing or re-figuring your braking markers. In comparison to the OEM MS, you'd be getting approx 12% more braking power.
 

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If I know correctly, then OEM master has 16mm piston. 19mm piston has 41% bigger hydraulic area, meaning you need to sqeeze lever much harder to get same braking deceleration. No good upgrade unless you feel OEM is way too sensitive.
Brembo recommends RSC17 for small piston calipers (OEM). And I doubt you get meaningful improvement from MC upgrade, unless you are fast racer and they upgrade pads, calipers, disks first on gen5. Get best pads and see from there.
 

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Have heard good things from various friends about upgrading the stock brake lever/master cylinder to a 19mm unit

Wanted to understand if its worth putting down approx $300 on a Brembo RCS 19 and how drastic is the performance upgrade with this. Anyone who has done this switch?

I use my bike mainly at the track and for quick weekend rides.

Thanks a ton. :biggrin:


I fitted the RCS 19 CC couple weeks ago! Only ridden a couple times since but im loving the feel from them!

Some people dont like it but IMO its worth doing!
 

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2021 ZX10R Street & 2016 ZX10R KRT Race build
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I had high hopes for the Gen 5 Brembo, but I did not like it at all. I rode/tested 3 other Gen 5 and after bleeding...still felt weaker.
I will say that on my race bikes since 2005 I've always used some sort of Brembo MC, and swapped out most of my MC with a Brembo also.

My current Gen 5 I swapped out to a RCS 19 with in 5 months of getting the bike. That along with Vesrah Pads...night and day difference. Its the combination that give me the "feel" I am looking for.
 
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If I know correctly, then OEM master has 16mm piston. 19mm piston has 41% bigger hydraulic area, meaning you need to sqeeze lever much harder to get same braking deceleration. No good upgrade unless you feel OEM is way too sensitive.
Brembo recommends RSC17 for small piston calipers (OEM). And I doubt you get meaningful improvement from MC upgrade, unless you are fast racer and they upgrade pads, calipers, disks first on gen5. Get best pads and see from there.

braking and lever "feel" is a very personal style preference... so just because the factory system might be able to achieve adequate maximum braking doesnt mean that if "feels" great to all riders during normal and moderate usage.

a rider will perform better and be safer with a braking system that feels comfortable to them, so there is no harm in changing ratios to achieve that, as long as they arent losing any braking ability compared to the factory setup, which they arent.
 

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If I know correctly, then OEM master has 16mm piston. 19mm piston has 41% bigger hydraulic area, meaning you need to sqeeze lever much harder to get same braking deceleration. No good upgrade unless you feel OEM is way too sensitive.
Brembo recommends RSC17 for small piston calipers (OEM). And I doubt you get meaningful improvement from MC upgrade, unless you are fast racer and they upgrade pads, calipers, disks first on gen5. Get best pads and see from there.
I think you have it backwards. With 19mm, you have to squeeze the lever less to get same power as 16mm piston. Issue is, 19mm is just too powerful for the Gen5's M50 calipers. I tried it and it's not good. It might feel like you have a lot of brake power but you don't that much modulation anymore. I could settle for RCS17, which I thought was a good compromise but that's it.

I've said it before and I'll say it again. OEM Brembo master is excellent. Andrew Lee won his Stock1000 Moto America championship last year with a Stock master AND even stock lever without a remote adjuster. He's doing the same this year again. I run it on my race bike as well, although with a zeta lever and zeta remote adjuster. It's great and I have no reason to change.

That said, it does feel like you have more travel (modulation) but it's by design. RCS19 (or 19x18) naturally has less travel and more firm feel to it but it doesn't mean you have to chase this feeling on the gen5. There is a reason why they paired the master and calipers this way. It works, very well. If you want to blow some money on aftermarket bling, get RCS17.
 

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I think you have it backwards. With 19mm, you have to squeeze the lever less to get same power as 16mm piston. Issue is, 19mm is just too powerful for the Gen5's M50 calipers. I tried it and it's not good. It might feel like you have a lot of brake power but you don't that much modulation anymore. I could settle for RCS17, which I thought was a good compromise but that's it.

I've said it before and I'll say it again. OEM Brembo master is excellent. Andrew Lee won his Stock1000 Moto America championship last year with a Stock master AND even stock lever without a remote adjuster. He's doing the same this year again. I run it on my race bike as well, although with a zeta lever and zeta remote adjuster. It's great and I have no reason to change.

That said, it does feel like you have more travel (modulation) but it's by design. RCS19 (or 19x18) naturally has less travel and more firm feel to it but it doesn't mean you have to chase this feeling on the gen5. There is a reason why they paired the master and calipers this way. It works, very well. If you want to blow some money on aftermarket bling, get RCS17.


Most non manufacturer parts that go on a motorcycle are chosen because of cost or to cater for a wider range of users. Not because they are a perfect match! Otherwise out GEN 5's would come with RCS17's as OE!
 

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I think you have it backwards. With 19mm, you have to squeeze the lever less to get same power as 16mm piston. Issue is, 19mm is just too powerful for the Gen5's M50 calipers. I tried it and it's not good. It might feel like you have a lot of brake power but you don't that much modulation anymore. I could settle for RCS17, which I thought was a good compromise but that's it.

I've said it before and I'll say it again. OEM Brembo master is excellent. Andrew Lee won his Stock1000 Moto America championship last year with a Stock master AND even stock lever without a remote adjuster. He's doing the same this year again. I run it on my race bike as well, although with a zeta lever and zeta remote adjuster. It's great and I have no reason to change.

That said, it does feel like you have more travel (modulation) but it's by design. RCS19 (or 19x18) naturally has less travel and more firm feel to it but it doesn't mean you have to chase this feeling on the gen5. There is a reason why they paired the master and calipers this way. It works, very well. If you want to blow some money on aftermarket bling, get RCS17.
I agree with most what you are saying, losing modulation with RCS19 etc. And with other members saying that most depends on personal preference and feel is personal matter.

However I think it is important to understand simple physics behind it.
If you get it backwards, then for example you may not be able to brake with one finger where you did before with OEM, just an example.

Is RCS19 more powerful?
I think "powerful" not good word. Better say bike deceleration, fluid pressure, lever travel and finger force applied to lever.
Comparing OEM or RSC17 with RCS19: Clearly with RCS19 to get same fluid pressure (same deceleration) there is less lever travel needed, but MORE finger force needed!
Using bigger piston 19mm master instead OEM 16mm or 17mm may feel better to many people at first part of braking when building up brake pressure.
Just more confidence inspiring feeling when "pulling relatively hard" creates that hard braking.
Secong part easying off, trail braking is different story, much easier to go down 60, 40, 20% on brake force with RCS17. Tried both on same day on gen4 where caliper piston is same.
Why can I modulate better with RCS17? Possibly because my fingers are more sensitive with lesser force range to lever. Or in other words with RCS19 leak of sensitivity with too tense fingers during trail brake zone.
Of cource its just my feel and opinion.
You have 36mm race calipers, then RSC19 is recommeneded size.
 

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I one finger brake and so hate the 19's. I'm not trying to be an internet Rossi but I one finger braked all day at Road America on Monday with the OEM master and it performed great. A little fade yes but that's to be expected.

My recommendation is to save your $300 because it isn't going to make you the slightest bit faster and might actually make you slower. If you have ABS I would rip that shit out and have someone really good at bleeding brakes do the that job(if like me you are not). You are going to get way more feel and braking power.
 

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I will add that I just put the RCS19x20 Brembo on my ZX-10R. I did it because I had it laying around from when I was trying to correct brake issues on my CBR (which the master didn't fix). I was evacuating the entire system so I figured I may as well do the swap now. The problem I was having is that I was boiling the brake fluid. I did a flush with Castrol RBF but I believe I didn't get all of the stock fluid out. I took everything apart to its individual components, all of the lines, caliper pistons, etc.

Everything was flushed, blown, dried and reassembled and new AP R4 brake fluid put in (along with the RCS). The problem I was having, as mentioned was the fluid boiling and after a few laps my lever would get spongy and I'd have air in the calipers. The work I did fixed the problem but the lever feel isn't much different, though the pull is shorter and the I can/must squeeze a bit harder.


Personally, having run both, I'd stay with the stock setup and just put in the best fluid you can find, flush it often, and run high end pads.
 

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Discussion Starter · #12 ·
Thanks chaps. Basis the varying feedbacks I have read on the post, I will put this off for a while. Will first invest in better brake fluid and pads to see if the feedback improves. I already have a habit of bleeding the brakes every year and putting in fresh fluid.
 
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