My own JK 'Big Brake' research:

Majik

Majik

Member
I hope that TF isn't put out by my research. They have provided a great product - in fact, one of the only on the market. I just want to see if its possible to get even more brake power using OEM parts, and incorporate rear brake upgrades too. 37+" tires in reality need even more power than the 13" TF rotors can provide. Its an appreciated upgrade, but for me, a dad driving his kids around in his rig daily, not a good enough upgrade. So my goal is to make a confidence inspiring brake system, not just a good enough one.
 
Majik

Majik

Member
Update:

I believe I found a 14" rotor that will literally drop onto our JK front hubs!! I'm so confident that I'm gonna just bite the bullet and buy one to test fit it! It is also thicker than stock. HUGE!! For those of us running a 5 on 5.5" hub, it can be easily drilled for that bolt pattern, and the hub bore can be enlarged. In fact, I already have secured a local machine shop equipped with a brand new CNC mill/lathe to do any mods I need to perform to rotors, caliper brackets, etc. Exciting stuff and one step closer!!
 
Prime8

Prime8

New member
Majik said:
Update:

I believe I found a 14" rotor that will literally drop onto our JK front hubs!! I'm so confident that I'm gonna just bite the bullet and buy one to test fit it! It is also thicker than stock. HUGE!! For those of us running a 5 on 5.5" hub, it can be easily drilled for that bolt pattern, and the hub bore can be enlarged. In fact, I already have secured a local machine shop equipped with a brand new CNC mill/lathe to do any mods I need to perform to rotors, caliper brackets, etc. Exciting stuff and one step closer!!
Click to expand...

Awesome! This is my new favorite thread, btw...
 
Majik

Majik

Member
jeeeep said:
awesome! can's wait to see it.
Click to expand...

I'll be sure to pull a wheel and test fit it tomorrow for ya! Snap a few pics and post. What I might do is mount the rotor, slide our stock caliper over it (without bolting it on, obviously, because on that big rotor it won't reach the knuckle), and put the wheel back on to see if my initial measurements are correct. The detailed numbers I measured last week showed that in theory, I should be able to fit a caliper on a 14" rotor and still squeeze it into even the factory 17" rims! We'll see!!

Oh, the suspense!! LOL!

Could you imagine what it would look like to have, say, a 14" rotor, and a huge dual piston caliper, something like that off a late model Ram 2500 diesel, tucked inside our wheels?? :shock: I also have as a possibility a 4-piston OEM caliper to investigate...

I work from noon until midnight tomorrow so the pics might be late in coming, but I'll try by best to get them up :)
 
jeeeep

jeeeep

Hooked
that's would be great! I upgraded my rotors to slotted, it helped a lot over stock...but would sure like more stopping power when towing.
 
Majik

Majik

Member
Picked up my brand new test rotor this morning - :shock:

That is a beefy, huge-ass beast! I'm gonna just have to test-fit it tonight... there's no way I will be able to wait until tomorrow.
For those of you with stock hubs, I think it's just gonna be a slide-on fit.


On a COMPLETELY separate note - I've looked at several of the custom built RockJock III axles out there and I keep wondering one thing - why the hell would they proudly advertise it as including stock JK calipers?? Seems to me that if you are paying that much for a custom, heavy duty axle, that re-using these tiny calipers is a joke...

Sorry...off-topic, I know :)

Pics of rotor tonight!!
 
Prime8

Prime8

New member
Majik said:
Picked up my brand new test rotor this morning - :shock:

That is a beefy, huge-ass beast! I'm gonna just have to test-fit it tonight... there's no way I will be able to wait until tomorrow.
For those of you with stock hubs, I think it's just gonna be a slide-on fit.


On a COMPLETELY separate note - I've looked at several of the custom built RockJock III axles out there and I keep wondering one thing - why the hell would they proudly advertise it as including stock JK calipers?? Seems to me that if you are paying that much for a custom, heavy duty axle, that re-using these tiny calipers is a joke...

Sorry...off-topic, I know :)

Pics of rotor tonight!!
Click to expand...

Completely anecdotal evidence ahead... I have read about a lot of failures with the rock jock, compared to the prorock.
 
P

popo344

New member
I have heard that the Jeep Commander is using 13 inch rotors up front and that the caliper bracket may bolt to the JKs. I havent had a chance to check this out myself yet. But I can try next week since my jk is up on jack stands at this time.
 
munstie

munstie

New member
popo344 said:
I have heard that the Jeep Commander is using 13 inch rotors up front and that the caliper bracket may bolt to the JKs. I havent had a chance to check this out myself yet. But I can try next week since my jk is up on jack stands at this time.
Click to expand...

That may be true but the Jeep Commander brakes suck.

2011 JKU 3.5 R.E. Longarm lift.
 
M

Md_rubi

New member
Majik said:
Picked up my brand new test rotor this morning - :shock:

That is a beefy, huge-ass beast! I'm gonna just have to test-fit it tonight... there's no way I will be able to wait until tomorrow.
For those of you with stock hubs, I think it's just gonna be a slide-on fit.


On a COMPLETELY separate note - I've looked at several of the custom built RockJock III axles out there and I keep wondering one thing - why the hell would they proudly advertise it as including stock JK calipers?? Seems to me that if you are paying that much for a custom, heavy duty axle, that re-using these tiny calipers is a joke...

Sorry...off-topic, I know :)

Pics of rotor tonight!!
Click to expand...

What type of axles do you have?
 
Majik

Majik

Member
popo344 said:
I have heard that the Jeep Commander is using 13 inch rotors up front and that the caliper bracket may bolt to the JKs. I havent had a chance to check this out myself yet. But I can try next week since my jk is up on jack stands at this time.
Click to expand...

The Jeep Commander uses a 12.87" rotor with the correct bolt pattern and same hub bore diameter as the stock JK hubs. The rotor is slightly thicker (which is good) at 30mm vs the JK's 28mm. The overall "height" of the rotor (which includes the hat offset plus the rotor thickness) is 53mm, which is very close to the JK's stock 55mm. 'Height' is the industry standard term for this measurement. The floating calipers used in an OEM application will allow for a 2mm height difference. So the rotor you mentioned is a good choice, HOWEVER...

I still think that if we are going to go through all of this trouble, we should try to get an upgrade that will produce a noticeable improvement. The caliper for the Commander has 2 very small 48mm pistons. The surface area of our stock JK single 66mm piston is 3420 sq mm. The surface area of the TWO pistons combined in that Commander caliper is 3620 sq mm. This is only about a 6% improvement. Each caliper costs about $135 for only a 6% piston area increase. For contrast, a Dodge Ram 2500 caliper costs about $80 including eating a core charge and has a piston area of 4926 sq mm, which is almost a 50% increase! vs stock JK. I mention this because I'm trying to get us all the most bang for our hard-earned bucks! :)

Another problem is that for some odd reason, that caliper uses a non-metric brake line bolt thread. So you can't bolt your factory brake lines to that caliper. I know....what a PITA. It's these little details I'm trying to incorporate...

Please keep any and all suggestions coming and I will research every one!!
 
Majik

Majik

Member
14.2" rotor mock up!!

How about a few sexy pics of a factory 14.2" (yes - you heard me right - not a 13"... a 14") rotor sitting behind a stock JK rim??? Here ya go!!


First, the OEM setup:

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Now the two discs, stock and upgrade, side by side:

IMG_1329.jpg

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14" rotor on hub:

IMG_1334.jpg

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14" rotor behind wheel

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14" rotor behind wheel, with stock caliper

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The discussion:

So the rotor fits beautifully!! The only catch I found is that the outermost edge (facing the back of the wheel spokes) of the stock JK caliper contacts the rim. This is solely an issue with the stock JK rim, due to an approx 1" raised lip imediately behind the spokes that effectively narrows the inner diameter of the rim by nearly an inch. This is only an issue on factory rims. If you are running at least a 1" spacer behind your wheels, or any wheel with at least 1" LESS backspacing that stock (approx 5.25" or less, which is MOST JK aftermarket rims), then this isn't an issue.
It is so close that I still was able to lightly place the rim on the wheel studs long enough to take a few pics.

Given the simple physics behind braking, I feel that pushing the envelope for the largest 'fittable' rotor as possible is the easiest way to the most noticeable braking improvement. The gross brake torque increase in this case, if you were able to simply reuse your factory caliper, is 19.3%!!! Again, that is without change in master cylinder, and no change in caliper. Nearly 20% better!!! YAY!! :rock:

So....

Isn't that a big-ass, sexy rotor??! Look at the side by sides of the two rotors on the floor next to each other!! DAMN...! :eek: We are one step closer!!

Up next: calculations comparing master cylinder bores to the caliper piston area sizes. This is something that, to maintain a stock-feeling (or better) brake pedal, must be kept in mind!

After that, finding a suitable, big-ass (but low-profile) caliper! Stay tuned!!
 
Majik

Majik

Member
jeeeep said:
wow! what about wheel studs, I imagine they may need to be upgrades and a longer?
Click to expand...

No. Rotor mounting flange thickness is same so no stud length changes are needed. No upgrades to those are needed. Now, if I was professionally wheeling/racing, and running 42" wheels, maybe I'd go to a 9/16" stud, but if I was doing that type of activity, I'd be running 8 lug hubs anyways. So... nope. No stud changes needed.
 
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