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OK....like they say..."and now the rest of the story".
I spent some time on-line exchanging e-mail and forum comments with a couple of friends. I was looking for personal experiences from those that had put in a valve to reduce the rear brake pressure and thus, the rear brake lockup. Within 24 hours, I had the first hand information I was looking for.
The colored arrow in the above picture is pointing to the brake line connection on the combination valve that goes to the rear axle on the TJ. This is the line that will be removed from the combination valve. A Wilwood adjustable proportioning valve, model # 260-2220, was purchased on-line (I obtained mine from www.jegs.com) for about $50 delivered to my door. I found other adjustable prop valves for less but decided to pay the extra $10 and get one with the Wilwood name on it. The adjustable valve allows pressure to be reduced to a maximum of 57% of the inlet pressure by simply turning the adjustment knob. The valve is put in-line (after the combination valve) with the brake line feeding the rear axle and adjusted so that the rear brakes lockup just after the front brakes begin to lock.
Here is what the Wilwood adjustable proportioning valve looks like. How you decide to hook up the adjustable proportioning valve is entirely up to you. Here is how I decided to do it (not saying it is the best method, but it worked for me.)
The Wilwood valve comes with two adapters that you screw into the inlet and outlet ports. I have installed one of these and it is shown in the above picture as item #1. It is designed to take a standard 3/16" brake line flared connection, which is what item #4 is....a 20" long pre-flared line. Item #5 is a flared fitting that was salvaged from the line that originally connected the stock master cylinder to the combination valve. It is a metric fitting (a 14mm brake line wrench fits it) and just happens to be the same size as the one which appears in the picture at the top of this page (the one with the colored arrow in it). Item #2 is an adapter that I picked up at the local NAPA store. It is sized to fit fitting #5. I had picked up a couple of regular 3/16" fittings (items #3) before I found item #4 that came with the same fittings (hey, it never hurts to have a few extra brake fittings, right?)
By now, you should be able to figure out what is going to happen. Brake line #4 was cut (not all 20" of it is needed). One of the fittings on it was used and the other one was removed. In its place, fitting #5 was slipped onto the line. The end of the line was then double flared. This finished line was used to connect the combination valve's rear brake port (colored arrow in photo at the top of the page) to the inlet port (item #1 on the Wilwood valve). The rear brake line (previously removed from the combination valve) was then attached to the outlet port of the adjustable valve (item #2 on the Wilwood valve).
Here is the Wilwood proportioning valve as installed in the TJ.
I located it below and slightly forward of the combination valve. The most
forward port on the combination valve, which is the single line that goes to the
rear axle, is now connected to the outlet port on the Wilwood valve. The
section of brake line that I cut and flared myself now connects the combination
valve's rear line port to the inlet port of the Wilwood valve.
Here is another picture with the camera backed off just a bit so you can get a better idea of where everything is positioned. My plan is to make some kind of lightweight mounting bracket for the combination valve and the Wilwood valve so they can be connected together. Right now, everything is held in position by the rigid brake lines. I believe it would be better if things were supported by a bracket rather than the lines themselves.
MikeW was not able to make it over to help with the final testing due to some out of town company that came to visit. So, I got in contact with a couple of other Jeepers, Dan and Mark, and they agreed to come over Saturday AM and help out.
By the time Mark arrived, I had installed the Wilwood valve and was waiting for a spare pair of feet to actuate the brake pedal while I bled the air from the new lines. About the time we were finishing that up, Dan pulled up. After the typical 15 minutes of talking Jeeps and brakes and stuff, we headed out to do some deceleration testing.
I was a little apprehensive after the previous weeks testing. I set the Wilwood valve at the mid point and tried a couple of 35 MPH stops. The rears were still locking up so I dialed in a little more restriction on the Wilwood and gave it another try. Better....but still a little lockup on the rears. I gave it another 1 1/2 turns ( it is a 10 turn adjustable valve) to reduce rear pressure even more and then tried another stop, this time from about 45 MPH. Oh yes.....this time, we had the front tires howling (and I do mean howling). I split the difference from the previous adjustment and open the valve up a bit in hopes of getting the fronts and rears to lock up virtually together. Not too bad....several more 45 MPH stops indicated I was pretty darn close to a good front to rear bias.
By now, the tires and warmed up some and the smell of rubber was in the air. I wonder how many miles I burned off of the tires this morning? Oh well, all for a good cause. We broke out the tape measure and ran a series of 60~0 MPH stops. We got distances of 137', 140', 133', 107', and 144'. On the 4th stopping test, (the 107' distance), I tried something different. Instead of just hitting the brakes as I had been doing, I immediately let up on them (just a bit) when they started to howl and then reapplied the brakes very hard....kind of like doing a two step approach to stopping. In that stop, there was almost no tire howl on the second application of the pedal until just the very last few feet as I came to a stop. I was impressed with the results (and my tires were probably saying thank you too).
Van had told me I would have to learn how to stop all over again and although I didn't believe him at first, I was beginning to think that there was something to what he had said. The longer stop (last one) was an attempt at hitting the pedal three 3 times...(hey, if two times improved things, three times would be better, right?)...but I found that there was too much time wasted in the motions of releasing and reapplying the brake pedal...which resulted in a longer over all distance. So yes, I can stop in a shorter distance but it will require me to practice this procedure a few more times in order to gain the most benefit from it. Here is the video that was taken while we were testing the new setup. As you can see, the howling brakes was not the shortest stopping distance....having them just at the edge of locking up yielded the shortest distance (but I miss the cloud of blue tire smoke!) On the flip side of the coin, for those folks that have installed a 4:1 Tera or an AtlasII transfer case, you will see greatly improved results in your ability to stop the vehicle when in 1st gear and low range.
I think this about wraps up the install and testing. Am I happy with
the results....yes I am. I now have ample brake pressure to stop the
TJ. Do I need to work a little more on my technique, yes I do....no
different than adapting to any other modification that is made to the vehicle.
The change in brake pedal behavior is an added benefit, in my opinion. If
you are tried of trying to put your foot through the firewall in an attempt to
stop your vehicle, I would urge you to consider a Hydroboost.
Take care and remember to TREAD Lightly!