Spy photos of custom disk brakes on TJ knuckles.

[mrblaine]

Coming soon. Hopefully before the edit time runs out.

I designed and had Jack machine some custom brackets to bolt Wilwood 4 piston calipers on Kat's TJ. The stock knuckle was modified by removing the original pad ears and then machined flat, drilled and tapped to accept the bracket. The calipers develop 4800 lbs of clamping pressure at 1000 psi of line pressure. They are fixed calipers with floating pistons.

Larger diameter rotors give a slight mechanical advantage over the stock ones. These rotors are separate from the hat, and bolt up with 5/16-24 alloy socket screws. This saves machine work to the rotor if the need for replacement ever comes up. (you have to have machine work done to the hat section to do the hub conversion)

I am hoping that this will solve the TJ's poor braking with 35" and larger tires. I have a WJ master cylinder ready to bolt in to provide more correct volumes to the custom disk brake conversion I did on the rear 44. This master has a dual bore for dual disk set-ups. They measure 34 mm for the front and 24 mm for the rear. The stock TJ master is 1" straight through. A concern is that the stock booster may not develop enough assist with the larger bore to make the Wilwoods work correctly. If this turns out to be the case, I will swap in a larger dual diaphragm booster from a GM product and use a Corvette disk/disk master.

This is all prototype work for a kit that CTM will be selling if all works as planned. I have been able to generate enough line pressure in my TJ to bend, fold, and mutilate, brake pads, shoes and backing plates. This does not take into account leaky rear wheel cylinders. The stock stuff is just not strong enough to withstand high line pressures.












It is not who you know, It is who knows you

Jeeps do not make jeepers, jeepers make Jeeps.

[Wumpy]

More drool items from Blaine engineering!

The cool thing is the simplicity of the changing break pads and disks now. I can't wait to see it stop. You could (urp) put low profile tires on it and I bet it'd out stop a lot of cars!

Lots o nifty things on that TJ, it's gonna be neat to see it in action!

I am doing this from home.

[Jim B]

Blaine,

Nice BBS, thanks for the invite. I recognize some of the people here and it seems like it will be a lot fun.

With regards to your testing on these brakes, I hope it goes well as I agree with you that TJs could improve their breaking power when 4 wheel disk is added all around.

No one to date really has any "bolt on kit" or simple add on modification to improve the breaking power when 35"+ tires are added. It would definite be a money maker for CTM. Hope it goes well.

The only thing I've done to improve my breaking power was to remove the oring from the stock master cylinder. It actually helped getting some of the missing power to the rear. It actually brakes better enough so I can live with it and decided to drop my hunt to improve it any further since I could not find anything worth while in the mod market.

I purchased the Explorer disk kit for the rear as it was the only one that I have personally seen work with regards to the ebrake... I actually have an ebrake that works quite well. Take this into consideration in your design.

Jim B.

97TJ El Niño, Mods listed on Web Site.
JJB@worldoversea.com
http://www.jeep.worldoversea.com

[mrblaine]

Jim- If you have the Exploder rear disks you should recognize the rear disks on Kat's. I bought the Ford parts and adapted them to the 44. About half the cost of SS brakes kit.

Simple job that only requires re-drilling the cast bracket and making a spacer ring to compensate for the additional thickness. This ring goes between the axle retainer and the tapered shoulder on the retaining ring between the bearing and the retainer.

It is not who you know, It is who knows you

Jeeps do not make jeepers, jeepers make Jeeps.

[Jim B]

Blaine,

That is exactly (if I recall when I last took the axle out) how mine installs. You have the flange axle, the set 20 bearing, pressed spacer. You then have the loose ring spacer and the bracket the hold the axle over that.

Here is my wish list. Have or make a bolt on (or maybe a close bolt on) master cylinder (or if need to also a booster) that will handdle the stock two intake lines that will provide good breaking power to both the rear and the front. 70/30 or 60/40. Making sure that the new master or maybe booster does not throw off the computer and does not take up any more room than the stock set up that is on there now due to other installs around that area.

This would be a money maker. Have the kit in two parts, one that includes both the rear disk set up and master/or booster setup, and one that includes the master/or booster only for those who already have disk in the rear.

I know I ask for alot, but someone told me once... ask and you shall receive.

Jim B.

97TJ El Niño, Mods listed on Web Site.
JJB@worldoversea.com
http://www.jeep.worldoversea.com

[This message was edited by Jim B on June 25, 2001 at 06:08 AM.]

[This message was edited by Jim B on June 25, 2001 at 06:09 AM.]

[mrblaine]

Jim- I have been developing that kit for the last year and a half in association with Master Power Brakes. We currently have a version on a rig from a popular e-zine.

The difficulty lies in the small and relatively weak components of the stock TJ stuff. We even went so far as to have custom 10" high gain dual diaphragm boosters made. It is still difficult to make the stock components work correctly.

This is why I approached the problem from a different angle with Kat's rig.

Brake bias on a stock TJ is near perfect. The system is well balanced and very safe. Most people incorrectly try to introduce more rear braking. This is solving the problem from the wrong end. You do not want the rear brakes to lock up first. Jeeps are just miniature trucks. If the rear locks up first, it will come around on you on rain slick streets. This is a bad thing. You want the fronts to lock first and then the rears so that as you release the fronts slightly to induce steering, the rear will not be locked.

Small bit of trivia to help with brake bias. The best brake bias in the world on a production vehicle is on a Porsche 911. Even on this vehicle the fronts still do 64 percent of the work. It is difficult to overcome gravity, inertia, and higher COG and have the fronts on jeeps do less than around 85 percent.

The Rear brakes on a stock TJ are so touchy that the 00's have gone so far as to remove a strip of brake lining out of the center of the rear shoes. The rear brake shoes have only two strips of lining on the outer edges of the shoes about 3/4's of an inch wide.

It is not who you know, It is who knows you

Jeeps do not make jeepers, jeepers make Jeeps.

[Robert J. Yates]

Blaine,
How much do you figure the kits to cost from Jack?

Hey Jim B - welcome to out little piece of the world.

98 TJ Sport
D44ARB/D30Detroit/Teralow/Swampers
www.geocities.com/yatezess/

[Jim B]

Robert, thanks for the welcome, glad to be here.

Blaine,

I actually wanted to do this way back when I had my D44s with disks all around. I spoke to Harold over at Off Again offroad He now has some kits available for the CJs and YJs and he is still experimenting with the TJs.

He was the one that turned me on into removing the oring from the stock master cylinder. He stated that normally the ratio was 90/10 but since rear disk needs more pressure than drum it feels like you almost loose all of it in the rear. The problem multiplies itself with larger tires. He advised that by removing the oring there would be no limitation between the front or rear. There would be some small limitation to the rear due to the diameter size line and hole inside the master cylinder going to the rear. Hence the feeling of improving the rear to a higher percentage (who knows what).

There was one thing I also noticed while doing this quick fix is that the pedal was a bit more spongy and not quite as high. The benefits out weighed the cons.

He mentioned he was trying a few things out for the TJ but I just did not wish to be the test pig on this one. His idea would take up a lot more room which I did not care for.

Interesting the information that you bring forward about the Porsche and the true percentages all around. I do have to say that with this quick mod I can actually stop well still having less power to the rear like we are supposed to have. It would be nicer if I had the braking power I used to have (which I can hardly remember)when I first purchased the TJ.

Jim B.

97TJ El Niño, Mods listed on Web Site.
JJB@worldoversea.com
http://www.jeep.worldoversea.com

[pimp]

would the calipers develop 4800 lbs of clamping pressure at 1000 psi of line pressure if They are fixed calipers with floating pistons.

why would Larger diameter rotors give a slight mechanical advantage over the stock ones, These rotors are separate from the hat, 5/16-24 alloy socket screws saves machine work to the rotor if the need for replacement ever comes up. (you have to have machine work done to the hat section to do the hub conversion)

and what about the correct volumes to the custom disk brake conversion This master has a dual bore for dual disk set-ups. They measure 34 mm for the front and 24 mm for the rear. The stock TJ master is 1" straight through. the stock booster may not develop enough assist with the larger bore to make the Wilwoods work correctly. why not swap in a larger dual diaphragm booster from a GM product and use a Corvette disk/disk master.

[Hellbender]

It was my understanding that removing the O-ring made the porportioning valve the same as the ZJ's, is this info incorrect???

My brakes are very well balanced now, but I've still got the 33's on, I'll have to see what the 35's do (hopefully next week).

2000 TJ 4.0L, A/T, all factory options.
Jeep Rater Score 360
http://www.hellbender.rockcrawler.com/
NRA Lifetime Member

[mrblaine]

HB- removing the o-ring is something that I recommend against. It defeats the purpose of the combination valve. The c-valve is a complex little piece of engineering that allow the fronts brakes to engage just slightly before the rears do. It also keeps a bit of residual pressure on the fluid to minimize pad and shoe travel when applying the brakes.

I know that several modifiers of jeeps do this to the combo valve, but until I know exactly what the cause and effect are, I plan on leaving it alone and solving the problem differently.

If I knew exactly what the purpose of the o-ring was it might make it easier for me to do.

It is not who you know, It is who knows you

Jeeps do not make jeepers, jeepers make Jeeps.

[Jim B]

Blaine,

I agree with you that the problem should really be solved differently. Sometimes some of us do not have the resources or knowledge that others have in order to try, test, machine work, etc.

I was a bit concerned at first to try this out. Since I really did not have any other resources available to me I decided to try. I made sure that the procedure could be reversed in case of a screw up. I actually took it out and placed it back several times until I decided to leave it off. From the testing that I did (don't know how valid) it "seems" that the oring acts like a limiting flow to the rear.

I do notice that the fronts still lock up first before the rear. When I was running with the oring I could never even get close to locking the rear like I used to way back when I was a stocker right out of the dealership.

What is the funtion of the oring from the above statement? I still don't know, I can only speculate from what I tested. I guess since the procedure is reversable one can try it, if it does not work out put it back. I din't even have to bleed the brakes when I was doing this.

Btw, I just noticed that the post times on the BBS is Pacific and not local to the user. Wow! never been up this early.

Jim B.

97TJ El Niño, Mods listed on Web Site.
JJB@worldoversea.com
http://www.jeep.worldoversea.com
Jeep Rater Score: 42

[mrblaine]

Jim- no worries. I am just a little gunshy around brakes and tinkering with stuff that I don't really understand. I didn't mean to sound like you had done something wrong.

Point of perspective- I have no combination valve on my jeep. Just a tee and a adj. proportioning valve. I also do not recommend this to anyone as a means of adjusting the pressure to the rear brakes.

It is not who you know, It is who knows you

Jeeps do not make jeepers, jeepers make Jeeps.

[Scott Hill]

How many times to I have to tell you stopping is highly over rated

With stock TJ brakes and 36's it is like having ABS, cause there is no F'n way you are going to lock the breaks up

I guess that meens I have another thing I need to fix

a little TJ with a few mods check her out at www.real-jeeps.com

[mrblaine]

Scott- we should be doing some testing tomorrow.

It is not who you know, It is who knows you

Jeeps do not make jeepers, jeepers make Jeeps.

[Jim B]

Blaine,

No worries here, I knew it was your own opinion regarding taking chances. Each of us take, or not take certain chances that we must ultimately be responsible for with our own rigs. I'm sure all of us like to find out what will work or not.

Btw, I also was actually thinking when I was doing all of this, of using a T with a proportioning valve. Never did go through with it. I was worried about the vehicle computer and got a yellow streak down my back. How the heck did you get around it?

Jim B.

97TJ El Niño, Mods listed on Web Site.
JJB@worldoversea.com
http://www.jeep.worldoversea.com
Jeep Rater Score: 42