Different brake systems on the Mazda6? - Page 2 - Mazda 6 Forums : Mazda 6 Forum / Mazda Atenza Forum
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post #11 of 18 (permalink) Old 05-17-2019, 05:20 PM
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C'mon now I wasn't trying to be snarky. I'm serious. It takes the same pressure to push more volume. You cannot make up for less volume with more pressure and vice versa. They are separate forces. All brake systems run at nearly the same pressure. They do not all deal with the same volume, that is why we have so many different sized master cylinders.


If you switch a car with drum brakes to discs you cannot use the same master cylinder because disk brakes require more volume of fluid to work.



It's the same by putting large brakes/calipers on any vehicle. You have to ensure it has the right volume or they do not work optimally.



If you had the right master on your car your brakes would not only have noticeably better initial bite, they would fade less as well as clamp harder under extreme braking. Every bit of your braking experience would improve with a proper master.

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post #12 of 18 (permalink) Old 05-17-2019, 11:42 PM
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Quote:
Originally Posted by b1lk1 View Post
Doesn't matter if you post it twice,
You are right... I was thinking the same thing actually. Mine was a mistake however.

Quote:
Originally Posted by b1lk1 View Post
It is simple science, Google is your friend if it still doesn't add up.
Thanks for the suggestion.

I found this on a web site that does custom drag racing brakes, but maybe those are different and don't work the same.

"One of the most common misconceptions is that a larger master cylinder will create more pressure"
- Mark Williams Enterprises

I will add one more thing that I think will help and then resign, as this should really be in its own thread.

The only time the piston is moving (requiring volumetric change) is when the pad is moving from its resting position to making contact with the rotor. Once this slack is taken up the pad is in contact with the rotor (from both sides) and only compresses microscopically. Does the rotor really get narrower as you apply more brake force? Therefor, once the brake pads have made contact with the rotor there is no need to move any addition fluid volume as the pistons are not moving. All additional pedal force does is increase pressure. The pedal will move with increased force (from foot) as lines expand, mounting brackets flex, pedal arms flex, air is compressed, etc... The whole reason that we use liquid is to minimize that compression and movement to only the pads via the piston{s}.
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post #13 of 18 (permalink) Old 05-17-2019, 11:43 PM
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Quote:
Originally Posted by b1lk1 View Post
Doesn't matter if you post it twice, it does not make it right. Volume is just as important if not more important, especially for rear brakes. It was more obvious on 80's/90's trucks with 1/4 " rear lines to feed the massive 13"+ drum brake systems. They simply required more volume.


As for Speed6 brakes with a stock 6 master, you are not pushing the same amount of fluid with the stock master. You get the SAME pressure with MORE volume with the Speed master. If you cannot grasp that you are trying to fill up bigger calipers with an undersized pump (master) then it should make more sense. The Speed6 master is identical in every way except for bore. This in no way effects pressure. It only effects volume.


It is simple science, Google is your friend if it still doesn't add up.
The rear caliper is actually the same between the models, the rear only has a larger diameter rotor. At least 06-08 cars. So there is no change in hydraulics there....just a difference in brake torque.

The bore diameter of the speed6 is 13/16....and so is the master on my car....and no I didn't change it. Is the earlier car different? I'm not sure. Is there something different with the speed6 one....yes...but what I'm not sure...but it has different part numbers. The only thing it really changed in this application is pedal feel... like @DrFeelGood says....it has gotten noticeably firmer since I swapped mine. The brakes are confidence inspiring.

The other argument I'd throw out there is Corksport for example offers multi-piston brake kit upgrades for the Speed6 and the regular 6...but neither contain a master cylinder as part of the package or a "fine print" caution that you should have an larger one. Nissan offered Brembo brakes as an option on the 03~04+ Spec V cars...both vehicles w/ or w/o had the same master cylinder as well.

You have to remember that that volume you talked about is filled up after the 1st brake pump up after the brakes are assembled. There is no air in the system in theory so there is nothing to compress other than the caliper piston on the pads. The volume of liquid doesn't really matter because its treated as a solid since it doesn't compress...Also the 80/90s trucks with the drum brakes are moving the wheel cylinders more than a normal disc brake caliper car. So perhaps in that app volume is more important.

I might not be explaining this stuff 100% but hopefully you get the gist of it.

Anyway here is the math
https://www.joesracing.com/master-cylinder-math/
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post #14 of 18 (permalink) Old 05-19-2019, 09:51 AM
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This sis my last attempt to explain it to you guys. I won't respond after this, not out of pettiness, it just won't make sense if I do.


So you are both telling me that a 1 1/18" pipe can flow the same volume of water at the same rate as a 7/8" pipe? Both pipes handle the same pressure as it is a different force. It should be painfully obvious now that the larger pipe will push MORE fluid at the SAME pressure.


Does not matter if the system is sealed. Again, I have never once discussed pressure as this has nothing to do with pressure. You need MORE volume to push on the larger surface area of the piston. It will take nearly the exact amount of pressure and force to push the larger piston.


IF that analogy does not make sense then think about cubic inches in engines. Take a 4.8L LSx and compare it to the 5.3L LSx engine. They use the identical block and cranckshaft. The only differnce is piston size and stroke. Piston size and stroke determine the VOLUME of the combustion chamber. The 4.8L and 5.3L have the same compression ratio so the PRESSURE is static. The only difference is VOLUME in the combustion chambers as the 5.3L has more VOLUME than the 4.8L which allows it to let more air/fuel in to make more power.


Anyhow, the one thing that stares out at me is that you were willing to spend at least twice as much on brakes for "performance" but changing the master is out of the question.


As for Corksport, they won't tell you to upgrade the master with their kit because it is not needed for safety reasons. Speed6 guys already have the proper master cylinder and regular 6 guys are likely to not care as they will feel a difference, but it will not be optimal. Besides that, the aftermarket for 1st/2nd gen 6's is DEAD. I' shocked when I see places still trying to price expensive simple mods for our cars, the 6 was never properly supported by Mazda as well as the aftermarket.


Anyhow, you can think any way you want, this is high school science.

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post #15 of 18 (permalink) Old 05-19-2019, 06:50 PM
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I suppose I lied. I got sucked in by the Seiya effect.

Quote:
Originally Posted by b1lk1 View Post
So you are both telling me that a 1 1/18" pipe can flow the same volume of water at the same rate as a 7/8" pipe?
No, not at all. If they handle the same volume of water it would have to be at different rates.


Quote:
Originally Posted by b1lk1 View Post
Both pipes handle the same pressure as it is a different force. It should be painfully obvious now that the larger pipe will push MORE fluid at the SAME pressure.
Correct. P = F / A
Fluids are treated as a solid because they do not compress (much).

Quote:
Originally Posted by b1lk1 View Post
Does not matter if the system is sealed
Incorrect. If the system were not sealed you would never be able to generate the force (pressure in PSI) to move the caliper piston. Try opening your bleeder (any one of them) and see how you stop.

Quote:
Originally Posted by b1lk1 View Post
Again, I have never once discussed pressure as this has nothing to do with pressure.
Incorrect. Braking systems are all about pressure. If you cannot generate pressure against the caliper piston it will not move and squeeze the disk rotor to stop its rotation.

Quote:
Originally Posted by b1lk1 View Post
You need MORE volume to push on the larger surface area of the piston. It will take nearly the exact amount of pressure and force to push the larger piston.
Incorrect and correct. A contradiction to be accurate. Once the line is full of liquid it is essentially treated as a continuous solid.

Any force placed anywhere on the fluid column will be transmitted and shared throughout that column. The force placed at the head of the master cylinder plunger is the same as the force being placed outward on the brake lines which is the same as the force being placed against the entire surface of the caliper piston.



Notice in this diagram above how the volume is the same even though the diameter is different? Remember that the pressure throughout this will also be identical.
If the column to the right (the smaller one) were to increase in diameter (Speed6 master cylinder) it would mean that the distance the cylinder plunger (from the brake pedal) has to move would be reduced (to move the caliper piston the same distance). Pressure still does not change, only how far you have to push the pedal to do the same work [W = F D cos(Θ)].

Now, the moment the column on the left stops moving (pads make contact with the rotor) there is no need to move the column. The ability to move a volume of liquid is unnecessary because there is nothing left to move.

The only thing that will happen if you continue to press the brake (attempt to move the fluid column) is the pressure will increase. Remember P=F/A?
P= pressure
F= force
A= area.
The area cannot change because it is a fluid column (like a solid) and contained within steel (and some reinforced rubber brake lines)
That means as the force increases (from your brake foot through the master cylinder the pressure will also increase.

The pressure increase is the whole purpose of the system. More pressure against the caliper piston will force it against the pad and rotor harder. This will increase friction and you will stop the car.


Quote:
Originally Posted by b1lk1 View Post
IF that analogy does not make sense then think about cubic inches in engines. Take a 4.8L LSx and compare it to the 5.3L LSx engine. They use the identical block and cranckshaft. The only differnce is piston size and stroke. Piston size and stroke determine the VOLUME of the combustion chamber. The 4.8L and 5.3L have the same compression ratio so the PRESSURE is static. The only difference is VOLUME in the combustion chambers as the 5.3L has more VOLUME than the 4.8L which allows it to let more air/fuel in to make more power.
Unfortunately this analogy does not work. Excellent attempt as I really do appreciate analogies. Fuel is combustible and the rate of expansion within the combustion chamber is not linear for a number of reasons. This would be at the college level, not high school.


Quote:
Originally Posted by b1lk1 View Post
Anyhow, the one thing that stares out at me is that you were willing to spend at least twice as much on brakes for "performance" but changing the master is out of the question.
Not out of the question just unnecessary, and in my case diametrically opposed to what I want to accomplish, which is more braking force exerted on the wheels for the same amount of pedal effort.

Quote:
Originally Posted by b1lk1 View Post
As for Corksport, they won't tell you to upgrade the master with their kit because it is not needed for safety reasons. Speed6 guys already have the proper master cylinder and regular 6 guys are likely to not care as they will feel a difference, but it will not be optimal. Besides that, the aftermarket for 1st/2nd gen 6's is DEAD. I' shocked when I see places still trying to price expensive simple mods for our cars, the 6 was never properly supported by Mazda as well as the aftermarket.
Quote:
Originally Posted by b1lk1 View Post
Anyhow, you can think any way you want, this is high school science.
I think you will approve as I give credit to the Khan Academy where all the diagrams were taken from. It is a site for helping teacher explain concepts to students. Yes, it goes all the way to high school as well.


If it helps I can give examples of fluid dynamics as blood in cardiology, which is my training. It uses a multi-valve, 4 pump system but it is exactly the same principal and I have video and motion jpegs for those. It may be useful as it also shows how changes in artery elasticity affect pressure (think stainless steel brake lines here).
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post #16 of 18 (permalink) Old 05-19-2019, 10:06 PM
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Quote:
Originally Posted by b1lk1 View Post
IF that analogy does not make sense then think about cubic inches in engines. Take a 4.8L LSx and compare it to the 5.3L LSx engine. They use the identical block and cranckshaft. The only differnce is piston size and stroke. Piston size and stroke determine the VOLUME of the combustion chamber. The 4.8L and 5.3L have the same compression ratio so the PRESSURE is static. The only difference is VOLUME in the combustion chambers as the 5.3L has more VOLUME than the 4.8L which allows it to let more air/fuel in to make more power.
The 4.8L and 5.3L use different crankshafts (this is how stroke & volume is changed) & rods but the same bore. Better comparison, would have been to compare the 5.3L to 6.0L or 6.2L displacement versions as the bores are larger in those.

The reason why the static compression ratio *might* not change in the 4.8L/5.3L scenario (but it does), if you dig deeper, you will find that different flat top pistons in the LY2/L20 4.8L (~9.0 compression) and dish pistons in the LC9/LM7 5.3L (~9.5 compression) to increase combustion chamber size and reduce/offset the compression increase from the volume increase.

The actual combustion chambers of an engine does not have a whole lot to do with its stroke, but the bore does have some impact. It consists of the cylinder head volume + volume of the head gasket (bore matters here to determine volume) + volume of the piston top to keep it simple (there are a couple other variables, these are the major ones). To calculate the true combustion chamber of the engine is with the engine is at TDC...so stroke doesn't apply here. To calculate compression ratio, both bore and stroke are involved....it is the ratio of the cylinder volume w/ combustion chamber at BDC all smashed into TDC. So yes the pressure is changing.

A fun fact...you will find that using the 4.8L pistons in the 5.3L configuration will put the compression at about 10:1 vs its original 9.5:1. GM has a few versions of the 5.3L and the HO version was used here.

You are right here though the extra volume/displacement has a huge impact on power.

I've gone off topic. Its quite clear that @DrFeelsGood knowledge on the subject is well above my basic knowledge of fluid dynamics and he knows his stuff! So I now know what the Dr part of your name pertains too!
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post #17 of 18 (permalink) Old 05-20-2019, 11:51 AM
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Great discussion you have there. If there's any chance, I'd like to be a student of yours.

One thing I like in this forum, all responses, or most of all, are done in a professional manner and no personal attack is done to the person.

If a person makes a mistake, he readily admits it and moves on. If there's a disagreement on opinion, respect is given. If something is needed to be corrected, it is done in a polite manner.

I am thankful that I am part of this forum.
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post #18 of 18 (permalink) Old 05-23-2019, 07:26 PM
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Quote:
Originally Posted by b1lk1 View Post
If you used all speed brake calipers I hope you switched the master cylinder too as it has a larger bore to deal with the need for more pressure and volume for the bigger calipers.
Is it confirmed that the master is larger? I haven't had both in my hands but the all the info I've found for replacements have the master diameter as the same, so I've never strongly pursued changing it.

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