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Brembo M4 vs Brembo OEMs ?

Discussion in 'Tech' started by KneeDragger_c69, Mar 7, 2019.

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badmoon692008 Well-Known Member

nlzmo400r said: ↑
The larger rotor also has different thermal capacity and dissipation properties as you’ve mentioned. But for the sake of stopping power, the larger rotor has a longer lever on the wheel and therefore applies more torque to the wheel with a given brake pressure. Imagine a changing your discs to 80mm diameter discs. It would require 4x the braking force onto the rotors to stop the wheel than if you had 320mm rotors. Torque = Force x Distance. Sent from my iPhone using TapatalkClick to expand...
Hmmm... I didn't even think of that.. I wonder where the point of diminishing returns is for that? If bigger rotor = better then you'd think everyone would be running the buell brake set up.. Definitely something to think about though.
badmoon692008, Mar 13, 2019 #21
nlzmo400r Well-Known Member

badmoon692008 said: ↑
Hmmm... I didn't even think of that.. I wonder where the point of diminishing returns is for that? If bigger rotor = better then you'd think everyone would be running the buell brake set up.. Definitely something to think about though.Click to expand...
There's always a compromise. Larger rotors are going to be heavier. And you only need as much torque is required to lock the front wheel, the rest is for heat dissipation. This is exactly why the Buell was a single front rotor, there wasn't a need for 2 of that diameter. I remember a few years ago when MotoGP allowed the riders to use 350mm carbon discs, some teams switched and some didn't. Cal was riding the Ducati then (who switched to 350mm) and said the braking was violent and very physically difficult compared to the 340mm he was using prior.
nlzmo400r, Mar 13, 2019 #22
nlzmo400r Well-Known Member

KneeDragger_c69 said: ↑
Try looking for the piston size on Google and not finding anything. Will check it when I get in the garage. I think I'll stick with the RCS19 and leave things as is.... and see later on for, maybe, rotors 320mm.Click to expand...
I'd be surprised if you couldn't get what you wanted without just choosing the proper fulcrum with the RCS and the correct brake pad. Here's a very quick chart of hyraulic ratios I just made. Most stock 4 piston calipers come with either 32 or 34mm pistons. Typically the pistons of the caliper are equal in size. Most m/c piston diameters range from 15mm to 19mm. The table below is quick math on what the resulting hydraulic ratio would be with each of those setups. The higher the ratio, the more braking power you'll have for the same force applied by your hand on the lever. I did not take into account mechanical advantage of a different fulcrum of the RCS type m/c. Just remember if you choose shorter the fulcrum, more force will be applied to the brakes with equal force from your hand. You can see by the results, this is exactly why Brembo recommends the RCS17 (not the 19) for M50 equipped bikes (panigales etc). The m50 only has 30mm pistons, not the typical 34mm.
Last edited: Mar 13, 2019 nlzmo400r, Mar 13, 2019 #23
pittmeister Well-Known Member

nlzmo400r said: ↑
I'd be surprised if you couldn't get what you wanted without just choosing the proper fulcrum with the RCS and the correct brake pad. Here's a very quick chart of hyraulic ratios I just made. Most stock 4 piston calipers come with either 32 or 34mm pistons. Typically the pistons of the caliper are equal in size. Most m/c piston diameters range from 15mm to 19mm. The table below is quick math on what the resulting hydraulic ratio would be with each of those setups. The higher the ratio, the more braking power you'll have for the same force applied by your hand on the lever. I did not take into account mechanical advantage of a different fulcrum of the RCS type m/c. Just remember if you choose shorter the fulcrum, more force will be applied to the brakes with equal force from your hand. You can see by the results, this is exactly why Brembo recommends the RCS17 (not the 19) for M50 equipped bikes (panigales etc). The m50 only has 30mm pistons, not the typical 34mm. View attachment 152623 Click to expand...
Glad someone brought up this chart. It should also be noted that a master to slave ratio of in the range of 23-27 is the ideal compromise between feel/progression and power. You can see how the RCS17 with M50's and RCS19 with M4's would sit right in the middle of this range. nlzmo400r said: ↑
Whoops. Good catch! You’re right. I meant switch from 20mm to 18mm!! Weird that OPP also has it incorrect. The 18mm or 20mm distance is the distance from the lever pin to the fulcrum (plunger). So the closer to that fulcrum the pin is (18mm) the less force is required. The 20mm distance will require harder pull from the hand to net the same force on the plunger because of reduced mechanical advantage. Sent from my iPhone using TapatalkClick to expand...
Just to be pedantic, brake masters are a class 2 lever. The lever pin is the fulcrum and the plunger is resistance.
pittmeister, Mar 13, 2019 #24
nlzmo400r Well-Known Member

D’oh! I don’t mind pedantic if it’s going to make the statement correct! Thanks for your input. Sent from my iPhone using Tapatalk
nlzmo400r, Mar 13, 2019 #25
KneeDragger_c69 Well-Known Member

So if I read this correctly, a M/C 16 or 17 would be a good update... gather that my OEM Nissin pistons are 34mm. Wonder then why so many racers buy the 18 or 20 m/c ?
KneeDragger_c69, Mar 13, 2019 #26
nlzmo400r Well-Known Member

KneeDragger_c69 said: ↑
So if I read this correctly, a M/C 16 or 17 would be a good update... gather that my OEM Nissin pistons are 34mm. Wonder then why so many racers buy the 18 or 20 m/c ?Click to expand...
It would achieve what it seems you're searching for. It's uncommon because you're going quite far beyond the norm for m/c to caliper sizing. Again, I can't stress enough, make sure your pads are in good shape (not glazed), that your rotors are in good shape, that the pads are actual race type brake pads that have higher than 'street version' friction coefficients. And lastly, since you already have an RCS19, make sure the adjustable pivot is in the 18mm position. If all this is correct and you still feel the need to go to the 17 master cylinder - you'll have a more sudden brake bite that will require more travel at the lever, but the same effort from your finger. It will be less 'progressive.' I would even emphasize that if you decide on a RCS17, start with the pivot adjusted to the 20mm position first. For reference I have a daytona 675 which has 4 piston calipers. 2 pistons are 34mm and 2 are 30mm. So the effective surface area is 6455mm (basically the same as having 4 32mm pistons per caliper). I use an RCS19 on the 18mm fulcrum position and have what I feel is PLENTY of stopping power with CL59 pads on stock 308mm discs.
Last edited: Mar 13, 2019 nlzmo400r, Mar 13, 2019 #27
JCW Well-Known Member

KneeDragger_c69 said: ↑
So if I read this correctly, a M/C 16 or 17 would be a good update... gather that my OEM Nissin pistons are 34mm. Wonder then why so many racers buy the 18 or 20 m/c ?Click to expand...
Just for comparison, M4 calipers are 34mm. OEM gsxr600/750 MC are about 17mm. The lever travel was too long for my taste. I would stick with a 19mm bore and 18mm fulcrum distance. I don't know a lot of people who like the 20mm You have an RCS now, correct? and don't like what about the braking? I think it might be best to identify your problem first.
JCW, Mar 13, 2019 #28
JCW Well-Known Member

KneeDragger_c69 said: ↑
Thnx for the input... but I have already changed pretty much everything concerning braking, except for calipers and rotors. M/C is a RCS19, SS brake lines with splitter and SBS DC brake pads. Want more braking power, with out forcing with my hand (I get arm pump)Click to expand...
Try different brake pads first. Here http://www.vesrah.tokyo/racing-products/
JCW, Mar 13, 2019 #29
KneeDragger_c69 Well-Known Member

nlzmo400r said: ↑
It would achieve what it seems you're searching for. It's uncommon because you're going quite far beyond the norm for m/c to caliper sizing. Again, I can't stress enough, make sure your pads are in good shape (not glazed), that your rotors are in good shape, that the pads are actual race type brake pads that have higher than 'street version' friction coefficients. And lastly, since you already have an RCS19, make sure the adjustable pivot is in the 18mm position. If all this is correct and you still feel the need to go to the 17 master cylinder - you'll have a more sudden brake bite that will require more travel at the lever, but the same effort from your finger. It will be less 'progressive.' I would even emphasize that if you decide on a RCS17, start with the pivot adjusted to the 20mm position first. For reference I have a daytona 675 which has 4 piston calipers. 2 pistons are 34mm and 2 are 30mm. So the effective surface area is 6455mm (basically the same as having 4 32mm pistons per caliper). I use an RCS19 on the 18mm fulcrum position and have what I feel is PLENTY of stopping power with CL59 pads on stock 308mm discs.Click to expand...
Yup... pads are race, SBS DC (dual carbon) All good on that end on the finish of the pads and rotors. Did try DP Pads (RDP127) this summer... and prefered the bite of the SBS DC. I'll look into the RCS17... Thnx JCW said: ↑
Try different brake pads first. Here http://www.vesrah.tokyo/racing-products/Click to expand...
Never tried them... might give them a try this summer. Thnx edit: just my luck... was looking at the ZZ in the Vesrah and they don't make it for my bike.
KneeDragger_c69, Mar 13, 2019 #30
JCW Well-Known Member

Is this a track only or street bike? Sounds like the pads you use being carbon based require a lot of heat to function optimally. If you are not braking hard enough even on track (certainly on the streets), you would likely be better served with a sintered metal pad. This sounds like it might be your issue...
JCW, Mar 13, 2019 #31
gapman789 Well-Known Member

OP, EBC GPFAX pads. FTW IMO.
gapman789, Mar 13, 2019 #32
TWF2 2 heads are better than 1

nlzmo400r said: ↑
I'd be surprised if you couldn't get what you wanted without just choosing the proper fulcrum with the RCS and the correct brake pad. Here's a very quick chart of hyraulic ratios I just made. Most stock 4 piston calipers come with either 32 or 34mm pistons. Typically the pistons of the caliper are equal in size. Most m/c piston diameters range from 15mm to 19mm. The table below is quick math on what the resulting hydraulic ratio would be with each of those setups. The higher the ratio, the more braking power you'll have for the same force applied by your hand on the lever. I did not take into account mechanical advantage of a different fulcrum of the RCS type m/c. Just remember if you choose shorter the fulcrum, more force will be applied to the brakes with equal force from your hand. You can see by the results, this is exactly why Brembo recommends the RCS17 (not the 19) for M50 equipped bikes (panigales etc). The m50 only has 30mm pistons, not the typical 34mm. View attachment 152623 Click to expand...
Only one side of caliper is used for area. Here is another chart

Attached Files:
- mastercylinder copy.gif
  File size: 25.3 KB Views: 40
TWF2, Mar 14, 2019 #33
stangmx13 Well-Known Member

JCW said: ↑
Try different brake pads first. Here http://www.vesrah.tokyo/racing-products/Click to expand...
this. I switched off of the SBS DCs. they lack power, especially when they start to wear, and are terrible in colder conditions. If u want another low-bite pad like the SBS DC, u could try the Vesrah XX. that's what im using now. comparable bite, much more power. the SBS DCs are way cheaper. but ive found that they wear much faster than Vesrah XX. so total cost is about the same over an entire season.
stangmx13, Mar 14, 2019 #34 Bruce likes this.
nlzmo400r Well-Known Member

TWF2 said: ↑
Only one side of caliper is used for area. Here is another chartClick to expand...
Why is only one side of the caliper used for area if the fluid must move all of the pistons? Sent from my iPhone using Tapatalk
nlzmo400r, Mar 14, 2019 #35
nlzmo400r Well-Known Member

Now that I think about this more, you’re right. With opposed pistons, you'd only count half the surface area of the pistons because the forces are opposing each other. @KneeDragger_c69 just to clarify, this doesn’t change the fact that smaller m/c bore result in higher hydraulic ratio. But it does change the resulting ratio numerically. @pittmeister Where did you get the info of master to slave ratio in the 23-27 range being the ‘norm’? Is this an industry standard or something you’ve deduced from seeing what OEMs choose size wise? Here is the updated version of the chart I made with the corrected calculations of using half of the total surface area of the pistons for opposed 4 piston calipers Sent from my iPhone using Tapatalk
nlzmo400r, Mar 14, 2019 #36
KneeDragger_c69 Well-Known Member

JCW said: ↑
Is this a track only or street bike? Sounds like the pads you use being carbon based require a lot of heat to function optimally. If you are not braking hard enough even on track (certainly on the streets), you would likely be better served with a sintered metal pad. This sounds like it might be your issue...Click to expand...
Race bike.. I compete up here in Canada in the National series (www.CSBK.ca) stangmx13 said: ↑
this. I switched off of the SBS DCs. they lack power, especially when they start to wear, and are terrible in colder conditions. If u want another low-bite pad like the SBS DC, u could try the Vesrah XX. that's what im using now. comparable bite, much more power. the SBS DCs are way cheaper. but ive found that they wear much faster than Vesrah XX. so total cost is about the same over an entire season.Click to expand...
I've enjoyed them for some years and never got into Vesrah's cause they never had the model I wanted back when I was riding the ZX6R '07. And now would go for the ZZ and again, not available for my bike ZX6R '13. Might go for the XX Really happy I made this thread, as I've learned so much. Can't thank enough @nlzmo400r for all your expertise and everyone that pitched in. Always nice to see a community come together.
KneeDragger_c69, Mar 14, 2019 #37 JCW and nlzmo400r like this.
pittmeister Well-Known Member

TWF2 said: ↑
Only one side of caliper is used for area. Here is another chartClick to expand...
Did you get a chance to read that article that chart was attached to? It also states at the top that surface area is based on the number of pistons. https://www.vintagebrake.com/mastercylinder.htm nlzmo400r said: ↑
Now that I think about this more, you’re right. With opposed pistons, you'd only count half the surface area of the pistons because the forces are opposing each other.Click to expand...
You are going to have to clarify your logic a bit more for this statement.
pittmeister, Mar 14, 2019 #38
nlzmo400r Well-Known Member

pittmeister said: ↑
Did you get a chance to read that article that chart was attached to? It also states at the top that surface area is based on the number of pistons. https://www.vintagebrake.com/mastercylinder.htm You are going to have to clarify your logic a bit more for this statement.Click to expand...
I had the relation right, but the math is backwards. My ORIGINAL spreadsheet was correct. I'll reattach it here. For 4 piston opposed calipers, you take into account the area of all 4 pistons, or 8 pistons if a dual caliper setup is being used. For SLIDING calipers, you double the area of the pistons because they are required to travel twice as far take make pad/rotor contact and therefore require the same fluid displacement as opposed piston calipers with double the number of pistons. E.G - 2 piston sliding caliper requires same fluid displacement as 4 piston opposed caliper. That being said, we probably need to agree on some definitions as well. He continues to call lower ratio (caliper area to m/c area) setups 'wooden' compared to higher ratios. I disagree. I would call a very high ratio wooden (that implies you're piling on force with your hand, but feel as if you're trying to compress a block of wood). I would call a lower ratio sensitive or less progressive, where the travel of the lever would be farther without much braking force, then suddenly much more force being applied at the disc because of the higher pressure produced by a smaller bore master cylinder. I know with all this back and forth it seems confusing to people who are just looking for answers, but keep in mind that none of this changes the principle. Smaller hydraulic ratios of slave (caliper) to master (m/c) will result in shorter lever travel requiring more hand force. Higher ratios, the opposite.
nlzmo400r, Mar 14, 2019 #39
TWF2 2 heads are better than 1

nlzmo400r said: ↑
I had the relation right, but the math is backwards. My ORIGINAL spreadsheet was correct. I'll reattach it here. For 4 piston opposed calipers, you take into account the area of all 4 pistons, or 8 pistons if a dual caliper setup is being used. For SLIDING calipers, you double the area of the pistons because they are required to travel twice as far take make pad/rotor contact and therefore require the same fluid displacement as opposed piston calipers with double the number of pistons. E.G - 2 piston sliding caliper requires same fluid displacement as 4 piston opposed caliper.Click to expand...
Is pressure different between sliding and opposed caliper with everything else been equal?
TWF2, Mar 14, 2019 #40