My own JK 'Big Brake' research:

turbineguy said:
I wouldn't think that circumference matters as much as area does. The area difference is significantly different.

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Also (to add to the above about piston size and pressure vs force) the distance from the center has a pretty big effect. To picture it, try tightening a bolt to 40 ft lbs with a 4" wrench, then try it with a 24" wrench. Now look at it from the other side, using his 6000 pounds of force, going from an effective radius of 12" to 14" is a little over 15% increase in the lever arm. This is a pretty significant increase. This doesn't take into account the increased mass of the rotor giving you a better heat sink which will help reduce temperature induced brake fade (as will the larger calipers).

Look at the mono-bloc brake calipers used in Moto GP. They are one piece and built for the absolute minimum deflection to give maximum breaking without the "spongy" feel. This is also why motorcycles go from the OEM brake lines to braided SS on sport bikes soften in aftermarket, the swelling in the line (even as super slight as it is) detracts from the performance of the braking system.
 
Thanks, Majik.
Majik said:
...The force is distributed evenly across the pad even though the piston is hollow.
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That was kinda my point with a multi-piston set-up.

Assuming the pads for your chosen caliper have a larger rotor contact area than that of the single piston pads, (and a rephrase of my question,) will it require more or less pressure to achieve the same level of braking?

My thoughts process...
More friction surface tells me it would take less pressure to achieve the same braking level, but spreading that pressure over a larger area tells me it would take more pressure. I just don't know which one is correct.

<edit> Ah, nevermind. It won't matter anyway. Your MC will take care of it. I was just trying to get some insight to the "feel" at the pedal.
 
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Zstairlessone said:
Also (to add to the above about piston size and pressure vs force) the distance from the center has a pretty big effect. To picture it, try tightening a bolt to 40 ft lbs with a 4" wrench, then try it with a 24" wrench. Now look at it from the other side, using his 6000 pounds of force, going from an effective radius of 12" to 14" is a little over 15% increase in the lever arm. This is a pretty significant increase. This doesn't take into account the increased mass of the rotor giving you a better heat sink which will help reduce temperature induced brake fade (as will the larger calipers).

Look at the mono-bloc brake calipers used in Moto GP. They are one piece and built for the absolute minimum deflection to give maximum breaking without the "spongy" feel. This is also why motorcycles go from the OEM brake lines to braided SS on sport bikes soften in aftermarket, the swelling in the line (even as super slight as it is) detracts from the performance of the braking system.
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This is true, however, not as important as you think. That was one of the things I've learned with this whole project. Yes, you gain potentially 15% brake torque with the larger rotor. That is the absolute max that you could even think of picking up with a stock rim size. However, 15% increase in braking friction is a piece of cake with the right pads alone (as I discussed recently), and 15% with the right caliper is also a piece of cake. Sooooo... If I back down to something like 13 or 13.5" on the rotor, we gain alot of wheel-to-caliper clearance over my original 14" rotor, but only lose 4-8% brake torque. I am upgrading to a 32mm thick rotor still, so we still gain a much better heat sink. However, I have learned that the right caliper and pads makes a MUCH bigger difference in brake power increase than simply squeezing the biggest rotor to the last 0.01" in the package...
 
Can you share a recommended a set of brake pads for the standard calipers to hold us over until you get this project finished? Are the pads compatible between the stock and upgraded calipers?
 
Thanks for the time and effort so far shared with all. I'm a noob here, been on a number of forums for a few year since getting my 12 model JKU CRD and only found this site as I was researching viable decent big brake parts ( in Australia we get the big brakes standard) that would come in slotted and/or drilled as well as a 5 on 5.5 stud pattern for the spyntech hubs.

Came across this topic by chance and had to join up to say thanks for all the effort you have put in and all the work it has just saved me.

Regards

Martin
 
So excited to see an end result and parts list. Hoping my stock brakes hold out but they are wearing fast! Thanks for all of your time and money spent on this Majik!
 
ufgeek said:
Can you share a recommended a set of brake pads for the standard calipers to hold us over until you get this project finished? Are the pads compatible between the stock and upgraded calipers?
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Great question!

Yes, since you have been researchign all these things, what is the recommended type of brake pad for best stopping ability, and is there much difference in brands?

I will probably be needing new pads before this full "Big Brake option" is complete, and well, I'm only going to be on slightly larger then stock tires right now, but would like better braking.

thanks again.
 
This is not the point of this thread but I thought it would be a fun distraction while you're working hard on a solution for our 17" wheels.

Dakota_Customs_15inrotors_4piscalipers_20inwheels.jpg
 
Majik said:
Found a great resource that has helped me more quickly narrow down some parts to compare bolt patterns, rotor specs, master cylinder specs, etc. It is through Centric's website. They are an OEM brake component manufacturer that produces and supplies a large portion of the OE brake parts. Through their catalog and reference tools, I was able to obtain measurements and specs on a large number of parts.

I think I may have found the master cylinder that Teraflex is selling as part of their 'Big Brake Kit'.

Here is the stock JEEP JK 2007-current master cylinder:

View attachment 25394


... and here is the master cylinder for a 2010-2011 Dodge Nitro!

View attachment 25395


So what's the difference? Well, first, what is the same: brake line port thread sizes match; overall dimensions of master cylinder and reservoir. There is a subtle 0.06" difference in the plunger lengths, but there is a threaded adjuster in most vacuum boosters to allow some tweaking. 0.06" is not anything to worry about. Many of those adjusters can accommodate almost an inch of play!

What's the upgrade?? The bore size is 1/16" larger.

So now for some math:

The stroke volume of a master cylinder is determined by: pi*bore radius*bore radius*depth of compression of plunger

Stock JK MC: 3.14159 * 0.5" * 0.5" = 0.7854 sq in (cross sectional area of cylinder bore)

2010 Dodge Nitro MC: 3.14159 * 0.53125" * 0.53125" = 0.8866 sq in

So what does this mean? If you depress the plunger of the stock JK master cylinder 1", you move 0.7854 cubic inches of brake fluid. If you depress the plunger of the Nitro master cylinder 1", you move 0.8866 cubic inches of brake fluid.

If you calculate the increase in volume as a percentage, that comes out to a 13% increase in stroke volume! Why is this significant? Because, ironically, Teraflex advertises a "14% increase" in fluid flow with their upgraded master cylinder!! Strikingly similar numbers, huh?? :)

And here's the fun part: The MOPAR brand replacement master cylinder can be yours for the amazing low price of: $56.49
Compared with the average price for the Teraflex unit of $190.
I haven't verified yet whether or not this replacement includes the reservoir or not, however, most of these late model ones I've researched do. And it appears, anyways, that the reservoir for this 2011 Nitro is the same as that on our JKs, so you could reuse yours, worst-case scenario.

I'll keep it coming as interest persists... much more to figure out here :) I like the potential $130+ savings already, though!! Honestly, though, I would really like to find a master with a bit bigger bore. 1.125-1.25" would be ideal, I think. But at least this is a start!!

Even if you don't decide to do any rotor or caliper upgrades, this could be an easy $60 upgrade on its own to add some good, solid feel to your brake pedal!
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Have you ever checked out the difference of the 2009-2010 JK's master cylinder ?! They are larger then the others !!!
 
snopro said:
Have you ever checked out the difference of the 2009-2010 JK's master cylinder ?! They are larger then the others !!!
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yep...teraflex uses the 2009-2010 master cylinder for their kit (they did when it was 1st released and I inquired about it).
 
wow, can't believe I just read this entire thread start to finish, awaiting final results :pop2:...I think the time and effort you put into this "project" is just awesome ! thank you!
 
I haven't read the whole thread - damn my dyslexia... So, how do i get better, bigger brakes? :thumb:
 
jeeeep said:
yep...teraflex uses the 2009-2010 master cylinder for their kit (they did when it was 1st released and I inquired about it).
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Actually I own a 2010 and when I upgraded with the TF kit and master cylinder the one that came was different than the stock one?? Thinking
 
But Majik is saying that the master cylinder from a 2010-2011 Dodge Nitro (not a Jeep) might be what TF is using in their big brake kit.
 
snopro said:
Actually I own a 2010 and when I upgraded with the TF kit and master cylinder the one that came was different than the stock one?? Thinking
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might be the nitro? - when I spoke to them they recommended I use my master cylinder since it was the same used in the kit, but as I said this was when they 1st released the kit.

I didn't buy the kit, I switched my discs to .... hell I forget now, but they are drilled and slotted with ceramic pads and that made a big difference - especially when I'm towing a loaded trailer
 
jeeeep said:
might be the nitro? - when I spoke to them they recommended I use my master cylinder since it was the same used in the kit, but as I said this was when they 1st released the kit.

I didn't buy the kit, I switched my discs to .... hell I forget now, but they are drilled and slotted with ceramic pads and that made a big difference - especially when I'm towing a loaded trailer
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Ok whew I'd hate to call J Thompson and give him a hard time about selling me a part I already had on my jeep
 
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