rear brakes not working correctly

[boogie94xj]

I put some disc brakes on the rear of my xj and I can't get them to work right. I kinda have a mixed bag of parts here...94 xj with the dual diaphram booster and master cylinder from a 95. Is there a bigger master cylinder that anyone has installed with as few headaches as possible? The reason I ask is that it just seems like I'm not getting enough pressure to the rear lines. Oh yeah, the rear hard line was replaced and I've bled it more times than I care to mention thinking there might be something in the line. Fluid flow easily and clear...no gunk.

 

[DaffyXJ]

Haven't put discs on the back yet, but I understand that discs take more line pressure than drums. You might need to upgrade the proportioning valve to get more pressure to the rears.

 

[boogie94xj]

Yeah, I tried that. The kit from SSBC has a procedure in it where the innards of the proportioning valve are taken out to boost the rear pressure...only helped marginally. Thanks for trying though.

 

[XgeekstarX]

i think you can take out a little o-ring in the proportioning valve that goes to the rear brakes and get a little better flow back there.

 

[johnsoninc86]

I just took the oring out of my 98 with zj discs on the back, and now i can lock up my 32's at will. You could always try and throw in a ZJ booster and proportioning valve thats already set up for discs. Good luck.

 

[Dingo509]

What calipers are you using in the rear? are you still running the stock front brakes? I have disc's on the rear of my D60 and it took me a while to get the pressure right. Turned out the Cadillac calipers i was using was not adjusting the piston correctly. So after i swapped som s-10 calipers on the brakes work great. I can lock up my 33" swampers on heavy beadlocks. BTW my XJ weights close to 5500 lbs. I just drove a friends XJ with the stock brake system and 33" and i noticed a huge difference in stopping power.

Dingo

 

[Dirk Pitt]

FYI.

Just because you can lock up the rear tires does not mean you are getting maximum benefit from your brakes.

 

[Dingo509]

FYI.

Just because you can lock up the rear tires does not mean you are getting maximum benefit from your brakes.

I agree with you 100% i was just stating that i can. Granted i have to put my foot down hard but it is possible. I know that if it happens easily that there is possible problem.

It could be looked at though, that if you don't have the ability to lock up the tires that you may not have the maximum clamping force available. Just a thought.

Dingo

 

[boogie94xj]

I believe they are the Caddy calipers. They have the built in parking brake.

 

[Dingo509]

Do some research on these calipers and you will find that the adjuster mechanism will stick and the pistons will not move out and therefor will not compensate for the pad wear. By swapping out the caddy calipers for some front calipers from an mid 80's s-10 i think your braking will improve drastically. The down side to this swap is that you will lose you e-brake, but this can be fixed by either buying reman caddy calipers or adding a driveshaft e-brake. if you have the correct s-10 calipers the pads will interchage with the old caddy calipers. If you have anymore questions feel free to PM me.

Dingo

 

[Cherokee91Red]

Removing the o-ring will help with breaking but is not ideal. My 8.8 discs will lock up much sooner than the 30's which I don't like. A new prop valve is in order. I think a 60/40 front/back pressure is ideal. I think you'll notice if you pump the brakes it allows more fluid to the front and will brake better.

 

[johnsoninc86]

Removing the o-ring will help with breaking but is not ideal. My 8.8 discs will lock up much sooner than the 30's which I don't like. A new prop valve is in order. I think a 60/40 front/back pressure is ideal. I think you'll notice if you pump the brakes it allows more fluid to the front and will brake better.

x2

That is one thing i dont like about mine. It still stops a hell of a lot quicker, but its kinda weird when the back end wants to swing around in front of you before the fronts even lock up. I think a ZJ prop valve would be a good choice.