blistovmhz
NAXJA Forum User
- Location
- Vancouver, BC
Hey all. I'm about at my wits end here.
A few years ago I stuck some KJ rear calipers on my XJ D44. At some point shortly after that, I also swapped out to the WJ knuckles with akebono calipers. At some point, my rear brakes just stopped being awesome and hoping someone may have the answer.
The problem is that the rears just won't work hard. With a regular bleed (starting at farthest corner and working my way to driver front), once I'm done I throw it up on stands, chuck it in gear and let it idle. With my 200lbs pushing to the floor, I can barely get the rears to stop, just working against idle. This was with my 4.0L/AX15 in first as well as my now 5.3L/4l65E, 4.56 gears. Something very wrong.
I figured out that if I pull one of the rears off and extend the piston a bit, then compress the piston back in with some big pliers, then re-assemble, the rears get much stronger, but still weak as hell. IE: They'll lock up on the trail, but almost nothing on the street. The front will lock up my 35's on dry pavement, but the rears do almost nothing. I gave up at some point because the fronts worked so well, but as I keep adding mass, I really need the rears working as well.
I burned through my first set of new rear pads in about a season or two and installed another set 3 months ago. That new set I just burned through the other day, so I picked up some more rotors/pads, realized my caliper pistons were a bit sticky so threw in some new calipers as well. Once again, when I bleed the system, the rears do almost nothing. I had my buddy put about 1" of brake pedal, which locks up the fronts to the point that I can't turn them by hand, but that same 1" leaves the rears barely grabbing.
I verified the prop valve was not closing off the rear (paper clip in the hole) until about 3/4 pedal, which is more than enough to lock up the fronts on dry pavement. I then cracked a bleeder open on the front caliper to test a theory. I figured it's gotta be a piston volume issue, and that the fronts were requiring far less fluid than the rears, so opening the fronts should allow my buddy to push the pedal down further, and sure enough, the rears lock up like they should.
So, what I figure is that despite the front's being dual piston from a WJ, they simply use less fluid volume than the KJ rears, so when I jam on the brakes, the fronts are fully engaged and thus preventing the pedal from travelling far enough to properly engage the rears. What kills me, is that both these calipers are used successfully (but seperately) by thousands of people. I figure it's gotta be that the combination of the WJ and KJ calipers just don't work together with a 50/50 proportion from the MC.
So that said, does anyone actually know? I've never found anyone else running the WJ and KJ together.
Also, assuming I'm right, and the rear volume requirement is just way higher, is there anything I can stick inline somewhere to properly balance the brakes? (ps. a prop valve does not have anything to do with front rear balance until your foot is on the floor. Modifying it doesn't help me because the fronts are already locked up well before the rears start biting, which is exactly the opposite of what a prop valve modification would do for me).
A few years ago I stuck some KJ rear calipers on my XJ D44. At some point shortly after that, I also swapped out to the WJ knuckles with akebono calipers. At some point, my rear brakes just stopped being awesome and hoping someone may have the answer.
The problem is that the rears just won't work hard. With a regular bleed (starting at farthest corner and working my way to driver front), once I'm done I throw it up on stands, chuck it in gear and let it idle. With my 200lbs pushing to the floor, I can barely get the rears to stop, just working against idle. This was with my 4.0L/AX15 in first as well as my now 5.3L/4l65E, 4.56 gears. Something very wrong.
I figured out that if I pull one of the rears off and extend the piston a bit, then compress the piston back in with some big pliers, then re-assemble, the rears get much stronger, but still weak as hell. IE: They'll lock up on the trail, but almost nothing on the street. The front will lock up my 35's on dry pavement, but the rears do almost nothing. I gave up at some point because the fronts worked so well, but as I keep adding mass, I really need the rears working as well.
I burned through my first set of new rear pads in about a season or two and installed another set 3 months ago. That new set I just burned through the other day, so I picked up some more rotors/pads, realized my caliper pistons were a bit sticky so threw in some new calipers as well. Once again, when I bleed the system, the rears do almost nothing. I had my buddy put about 1" of brake pedal, which locks up the fronts to the point that I can't turn them by hand, but that same 1" leaves the rears barely grabbing.
I verified the prop valve was not closing off the rear (paper clip in the hole) until about 3/4 pedal, which is more than enough to lock up the fronts on dry pavement. I then cracked a bleeder open on the front caliper to test a theory. I figured it's gotta be a piston volume issue, and that the fronts were requiring far less fluid than the rears, so opening the fronts should allow my buddy to push the pedal down further, and sure enough, the rears lock up like they should.
So, what I figure is that despite the front's being dual piston from a WJ, they simply use less fluid volume than the KJ rears, so when I jam on the brakes, the fronts are fully engaged and thus preventing the pedal from travelling far enough to properly engage the rears. What kills me, is that both these calipers are used successfully (but seperately) by thousands of people. I figure it's gotta be that the combination of the WJ and KJ calipers just don't work together with a 50/50 proportion from the MC.
So that said, does anyone actually know? I've never found anyone else running the WJ and KJ together.
Also, assuming I'm right, and the rear volume requirement is just way higher, is there anything I can stick inline somewhere to properly balance the brakes? (ps. a prop valve does not have anything to do with front rear balance until your foot is on the floor. Modifying it doesn't help me because the fronts are already locked up well before the rears start biting, which is exactly the opposite of what a prop valve modification would do for me).
