My own JK 'Big Brake' research:

[mrblaine]

With prior vehicles that I've upgraded brake systems on, I've noticed the same. The bigger the rotor, the more obvious the braking improvement. Even if keeping every other component the same. Thus why I'm really pushing with trying to make this 14" (actually like 14.2") rotor work. I'm kinda at a tough point right now though, debating the caliper. In theory, that nice shiny red 4-piston caliper I'm experimenting with has less piston surface area equivalent than any of several more common 2 piston floating calipers I could choose from, but it MIGHT make up for alot of that piston area loss because of its more rigid design and better distribution of "squeeze".

The math if correct shows a fairly large disparity. Given the improvements we've seen with the iron caliper bridge designs over the past few years, I don't know if that disparity is surmountable.

It also should, in theory, have the benefit of better heat dissipation. Like I mentioned earlier, it's just hard to come to an answer of which is a stronger brake without springing cash for 4 4-piston calipers and matching rotors, and ANOTHER set of 4 2-piston calipers and matching rotors and then doing back to back comparisons.

I'm not sure of the heat dissipation mechanism? The only difference I can see at this point is the bridge on one is a bit more closed but given the smallish amount of blocked area, I'm not sure that will even be noticeable.

I was hoping maybe the pressure film might help me avoid that big expense and give me good, hard data that wasn't just a "oh, system A feels stronger than system B".

One of the things that keeps me pursuing these 4-piston calipers, though, is that because of the effective piston surface area being smaller than other possible caliper choices, it should enable the use of either the stock or an only slightly larger bore 1 1/16" master cylinder. (Honestly, stock is likely to work great with these.)

Don't forget that the other oft-ignored aspect of swapping on larger calipers is you are essentially overdriving the pressure into them with the smaller than normal master.

I know there are systems out there that can be purchased right off the shelf that offer jeepers better brakes, and I'm appreciative of those vendors' solutions! I guess I'm just having fun trying to be the regular joe seeing if he can build a WOW brake system on his own, and using off the shelf stuff!! :yup:

It's all off the shelf at some point, eh? Anyway, my offer still stands, you need help with anything, I'm up for it.

 

[Majik]

You are over complicating it. This is as simple as plumbing in a line pressure gauge and then applying pedal pressure until you reach the same pressure on the gauge for both calipers. If you want further data such as how far the pedal travels at what pressure, that can be done as well, but the test to see which caliper exerts the most clamping force in what areas across the pad shape is relatively easy.

You are right. I understand that. I meant that I figured it would be difficult to manually apply pressure to the pedal in a controlled enough fashion to reach the desired MC output psi. I guess I was figuring that the output psi would be bouncing around by a few hundred psi if I was applying force simply with my foot. And if I had a goal of, say, 1500psi, and my foot 'twitched' a touch, I could spike up to 1700psi and then ruin the results on that particular piece of pressure film.

Maybe I have more control with my foot than I give myself?? :idontknow: The plumbing part I understood completely, though

 

[Majik]

The math if correct shows a fairly large disparity. Given the improvements we've seen with the iron caliper bridge designs over the past few years, I don't know if that disparity is surmountable.



I'm not sure of the heat dissipation mechanism? The only difference I can see at this point is the bridge on one is a bit more closed but given the smallish amount of blocked area, I'm not sure that will even be noticeable.



Don't forget that the other oft-ignored aspect of swapping on larger calipers is you are essentially overdriving the pressure into them with the smaller than normal master.



It's all off the shelf at some point, eh? Anyway, my offer still stands, you need help with anything, I'm up for it.

1. I agree. That's why I'm trying to do my own research to see why OEM vehicles with 'performance' fixed-caliper designs vs the same vehicle in a 'base' model with often larger piston-area iron floating calipers do so much better in braking tests. Is it simply the bigger rotors with the performance packages, or does the caliper contribute much? If it was only the rotors, one would think the OEM would use the big rotor with a cheaper floating caliper instead of big rotor and more expensive fixed caliper (with actually smaller total piston surface area in alot of cases).

2. Supposedly, the increased surface area of the fixed caliper housing plus the increased surface area of the larger number of pistons allows for better heat dissipation. Again...this is from what I've read, not what I've tested (yet).

3. True about the larger calipers - to get the same squeeze as OEM setup, I'd have to either push the pedal farther down (not desirable if you like a firm pedal) or use a larger MC bore. Because of the larger caliper piston surface area.

4. Don't worry, I'll be in touch I need all the help I can get!! I was just trying to get as much out of my limited resources first...besides...it's fun!!


Love this kinda stuff...hope everyone else does, too!!

 

[mrblaine]

You are right. I understand that. I meant that I figured it would be difficult to manually apply pressure to the pedal in a controlled enough fashion to reach the desired MC output psi. I guess I was figuring that the output psi would be bouncing around by a few hundred psi if I was applying force simply with my foot. And if I had a goal of, say, 1500psi, and my foot 'twitched' a touch, I could spike up to 1700psi and then ruin the results on that particular piece of pressure film.

Maybe I have more control with my foot than I give myself?? :idontknow: The plumbing part I understood completely, though

Anyone that has ever driven a vehicle with hydraulic brakes on it has nearly infinite control. Think about the last time you stopped at a signal light or stop sign and you were able to modulate the pedal perfectly without thinking to bring the vehicle to a near perfect stop right at the limit line. Most do this without ever thinking about what's involved and how awesome the computer between our ears is.

Even better is that you may have been slightly distracted when you first applied the brake to stop and then as your brain told you that the limit line was closer or further away, the foot automatically adjusted pressure to speed up or slow the vehicle down faster. It won't be as hard as you think to nail a 1000 psi output from the master repeatedly with very small variance.

 

[Majik]

Anyone that has ever driven a vehicle with hydraulic brakes on it has nearly infinite control. Think about the last time you stopped at a signal light or stop sign and you were able to modulate the pedal perfectly without thinking to bring the vehicle to a near perfect stop right at the limit line. Most do this without ever thinking about what's involved and how awesome the computer between our ears is.

Even better is that you may have been slightly distracted when you first applied the brake to stop and then as your brain told you that the limit line was closer or further away, the foot automatically adjusted pressure to speed up or slow the vehicle down faster. It won't be as hard as you think to nail a 1000 psi output from the master repeatedly with very small variance.

Awesome! That simplifies things, then So now I just have to play with a few squeezes with that pressure film using the 4 piston caliper vs a 2 piston floating, same master, same MC output pressure, and see what we get!

 

[mrblaine]

Awesome! That simplifies things, then So now I just have to play with a few squeezes with that pressure film using the 4 piston caliper vs a 2 piston floating, same master, same MC output pressure, and see what we get!

If it helps you at all, I've got a line on a new pair or several of the SRT8 44mm 4 piston calipers for a reasonable price. I've given this some thought and I think the difference is going to be the ability to get a larger rotor in the same area as a 2 piston pad driven within reason.

What I have played with that may be of interest in seeing if the predictions come true is taking the same dual piston caliper and moving it outwards with a 1" larger diameter rotor and all other things were equal. The performance increase wasn't enough to justify it's existence.

 

[DunnyBunny]

Anyone that has ever driven a vehicle with hydraulic brakes on it has nearly infinite control. Think about the last time you stopped at a signal light or stop sign and you were able to modulate the pedal perfectly without thinking to bring the vehicle to a near perfect stop right at the limit line. Most do this without ever thinking about what's involved and how awesome the computer between our ears is.

Even better is that you may have been slightly distracted when you first applied the brake to stop and then as your brain told you that the limit line was closer or further away, the foot automatically adjusted pressure to speed up or slow the vehicle down faster. It won't be as hard as you think to nail a 1000 psi output from the master repeatedly with very small variance.

Ok that's true because it basically happens subconsciously since its become habit and we do it everyday for tye most part. However tye game changes when we consciously do something to get desired results and are actually focused on the task. Sometimes it's even easier when we do this but sometimes it makes it harder for us to do this. And in everyday driving we don't have a pressure gauge in front of us telling us what psi we are applying to the breaks. To better clarify what I mean is say everyday driving. You know how your driving habits are, how fast you typically drive, what you do while your driving etc. but when you go take a driving test or something like that your focused on passing that test or doing everything right so you watch your speed more so you may stay under the speed limit or fluctuate a lot or break too soon or too fast or not fast enough etc. Or you may drive perfectly normal or even better than you normally do.

 

[DunnyBunny]

I hope all of the above makes since. Lol. I'm driving into work so its hard to focus on both things.

 

[mrblaine]

Ok that's true because it basically happens subconsciously since its become habit and we do it everyday for tye most part. However tye game changes when we consciously do something to get desired results and are actually focused on the task. Sometimes it's even easier when we do this but sometimes it makes it harder for us to do this. And in everyday driving we don't have a pressure gauge in front of us telling us what psi we are applying to the breaks. To better clarify what I mean is say everyday driving. You know how your driving habits are, how fast you typically drive, what you do while your driving etc. but when you go take a driving test or something like that your focused on passing that test or doing everything right so you watch your speed more so you may stay under the speed limit or fluctuate a lot or break too soon or too fast or not fast enough etc. Or you may drive perfectly normal or even better than you normally do.

I'd rather not clutter this with a debate over conscious versus subconscious, so the easier thing is to let you know that I have a line pressure gauge and have used it many times. It is very easy to push on the brake pedal and watch the gauge rise and be able to stop it at a given pressure.

 

[DunnyBunny]

I'd rather not clutter this with a debate over conscious versus subconscious, so the easier thing is to let you know that I have a line pressure gauge and have used it many times. It is very easy to push on the brake pedal and watch the gauge rise and be able to stop it at a given pressure.

Not trying to debate anything just trying to help the thread. My apologies. Majik great work. I read earlier bout someone mentioning reusing the front calipers and such for the rear brakes. You might have talked bout it in more depth but have you given that more thought or research or still focused on just the front for time being. Sorry again long thread and hard to go through it all.

 

[Prime8]

Nice! Yeah...I did similar...just kinda forgot about it. What was your major? Mine was mech eng. Now I'm an ER doc. Go figure! :idontknow:

I got my degrees in Materials Engineering. I worked in the Biodesign Institute at ASU while in college and I was in charge of finding a cheap, easy to work with polymer that can survive 6000 psi of pressure at the sea floor near hydrothermal vents to monitor the environment without the worry of losing one to the extreme temps of the vents. They were little, grapefruit sized "robots" that could be released in a swarm on the sea floor to float freely and transmit data to a relay hub that would then transmit to the surface.

 

[Prime8]

Prime8 is a metal god!!!

Sorry prime8 had after all THE thread. Lol.


(I hope you know I'm just giving you a hard time.)

Hahahahaha, at that time I was a polymer god. Haha. And that thread will only live in memory, since I'm pretty sure the "discussion" was either deleted or highly modified.

 

[Prime8]

Majik, just wanted to chime in to send out a reminder to everyone following along. And this might not be true any longer, but when I was using that pressure film a few years ago it was true...
The paper only turns pink, in varying degrees, not the full colors of the rainbow. You can either buy software from the company, or send in (carefully) your used paper to the company and they will image it for you and give you those cute computer images (that's how they get you, as the software/service isn't cheap). For the use of this project though, eyeballing the relative intensity in each area will be sufficient. Just keep in mind that the paper only turns pink. They make it by filling tiny (really fuggin tiny) glass spheres with a chemical, then sandwiching a thin and uniform layer of these spheres between two sheets of chemically treated paper. When the spheres crush under pressure, and chemical reaction turns a very localized section of the paper pink. As more spheres break, the color intensifies signifying higher pressure. You have to handle the paper very gently to not accidentally develop the film before your testing!

Just wanted to clear that up so no one thinks its like some kind of magical problem solving film. It requires an informed user, so with Majiks background, I give him my vote of confidence, for whatever that's worth. Hahaha.

 

[mrblaine]

Not trying to debate anything just trying to help the thread. My apologies. Majik great work. I read earlier bout someone mentioning reusing the front calipers and such for the rear brakes. You might have talked bout it in more depth but have you given that more thought or research or still focused on just the front for time being. Sorry again long thread and hard to go through it all.

It is a very good general rule of thumb that front to rear bias should be built around the front calipers providing twice as much braking force as the rears. If you move fronts to the back, then new fronts need to be twice as good as what they replaced.

Put another way, if you look at most OEM systems, if you see a 54mm dual piston front caliper, odds are high that the rear caliper will be a single 54. Again, rule of thumb as a lot of trucks, pick-ups, and rear or mid engine cars have different weight transfer rates.

 

[Majik]

Majik, just wanted to chime in to send out a reminder to everyone following along. And this might not be true any longer, but when I was using that pressure film a few years ago it was true...
The paper only turns pink, in varying degrees, not the full colors of the rainbow. You can either buy software from the company, or send in (carefully) your used paper to the company and they will image it for you and give you those cute computer images (that's how they get you, as the software/service isn't cheap). For the use of this project though, eyeballing the relative intensity in each area will be sufficient. Just keep in mind that the paper only turns pink. They make it by filling tiny (really fuggin tiny) glass spheres with a chemical, then sandwiching a thin and uniform layer of these spheres between two sheets of chemically treated paper. When the spheres crush under pressure, and chemical reaction turns a very localized section of the paper pink. As more spheres break, the color intensifies signifying higher pressure. You have to handle the paper very gently to not accidentally develop the film before your testing!

Just wanted to clear that up so no one thinks its like some kind of magical problem solving film. It requires an informed user, so with Majiks background, I give him my vote of confidence, for whatever that's worth. Hahaha.

Thanks for the update!!

:thumb:

 

[Majik]

I got my degrees in Materials Engineering. I worked in the Biodesign Institute at ASU while in college and I was in charge of finding a cheap, easy to work with polymer that can survive 6000 psi of pressure at the sea floor near hydrothermal vents to monitor the environment without the worry of losing one to the extreme temps of the vents. They were little, grapefruit sized "robots" that could be released in a swarm on the sea floor to float freely and transmit data to a relay hub that would then transmit to the surface.

Dude...

I was in Mechanical Engineering. Listen to this similarity: !! I worked on a project with NASA that investigated using large numbers of small, essentially 'disposable' robots to explore the surface of Mars. Avoiding the technical issues of sending a single, complex, expensive robot that if failed, the whole project failed. Each of our robots was equipped with a single sensor, and essentially relayed info to an orbiting satellite, to transmit back to earth. Our project focused on the idea that if 10 or 20 of our 200 little robots drove off a cliff and died...who cared?? It was so simple... they (at NASA) loved it. Fun days...

Crazy how similar our projects were?????!!!! :clap2:

 

[Prime8]

Dude...

I was in Mechanical Engineering. Listen to this similarity: !! I worked on a project with NASA that investigated using large numbers of small, essentially 'disposable' robots to explore the surface of Mars. Avoiding the technical issues of sending a single, complex, expensive robot that if failed, the whole project failed. Each of our robots was equipped with a single sensor, and essentially relayed info to an orbiting satellite, to transmit back to earth. Our project focused on the idea that if 10 or 20 of our 200 little robots drove off a cliff and died...who cared?? It was so simple... they (at NASA) loved it. Fun days...

Crazy how similar our projects were?????!!!! :clap2:

Hahaha, that's awesome! Space and deep oceans are the last, vast, unexplored regions and we've got them covered! Haha.

 

[Majik]

I've been doing alot of digging lately, trying to reassure myself that my caliper selection is valid. I found a nice piece of info: Wilwood makes a 'big brake upgrade' for the JKs now. It's cheaper than the $4400 Brembo upgrade...but it still costs about $2000 just for the front caliper and rotor. Nothing else. Still 'ouch' in my opinion. But here's the reassuring part: they just so happened to select a 4 piston caliper, using 44mm pistons, and a 14" rotor!!! The caliper I'm working with uses the exact same piston sizes, and the rotor is the same size, too! They also advertise that their system, because of the caliper selection they use, does not require a master cylinder upgrade! (Which is the same thing my calculations indicated for a 4-piston, fixed caliper with 44mm pistons.) This is EXTREMELY reassuring info. Now the only thing to determine is whether or not their upgrade's braking improvement is strictly due to the larger rotor, or if the fixed 4-piston caliper design actually adds power vs our stock floating piston design. On paper, the effective piston surface area is not any larger with their fancy, fixed design. But, as I've discussed before, the question is whether the more rigid, efficient caliper, combined with the much more even application of pad force due to the multiple piston design actually adds braking power. My suspicion is that yes, it does, and that it may be more noticeable than a simple comparison of caliper piston sizes might show. If it didn't add performance, why would auto manufacturers use them on their 'performance' models, like the SRT8 packages from Mopar, or the GT500 package from Ford, when they are in the business of making money? If a cheap floating caliper with one or two pistons with EQUAL piston surface area to a 4-piston caliper fixed caliper provided the same performance, and give them the same 60 to 0 times to post, I highly doubt they would fork out 3-4 times the price for a fixed caliper.

Guess it's time we prove that idea The pressure film I mentioned last week is being shipped and should be here any day. Then maybe we will have some comparisons of stock vs new caliper pressure distributions to view! All in all, I am going to continue with the 4-piston fixed caliper build, after coming across applications like the one from Wilwood that I mentioned above. I think we are on solid ground.

 

[Lil Nasty]

Sounds solid to me. Just need to paint "Majik-wood" on the side now.

 

[jeeeep]

the suspense! now I need to get the 37's and wheels selected and ordered in anticipation of brakes!
thanks for the update :beer: