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WARNING: Rear discs to strong???

A

andrew2516

NAXJA Forum User
Location
New Kensington, PA
I have new pads/ rotors and calipers all the way around with ZJ disc brakes in the rear. I also have the ZJ proportioning valve...which added braking power.

Anyway the braking characteristics seem to be slightly dangerous. The other day I was driving down the highway at about 75 and had to lock up the brakes. The ass end came around and almost put the jeep sideways in the middle of the freeway...some counter steer brought the jeep back under control but I can see how this could be a bad situation.

I know its probably the proportioning valve giving the rears to much braking power. I'm sure it doesn't help having a overly lifted jeep with 34" tires either but I thought I would just toss this out there for anyone who has this rear setup.

I do plan to put some bigger tires on the jeep so that might help me out later.

HPIM0929.jpg
 
mine don't seem to do that... I did leave the stock valve on. Also what did you paint your axles\calipers with?
 
Do a WJ brake/ knuckle swap and you will have better front brakes. It will also help your steering angles since you said it is overly lifted.
 
toysupra14 said:
mine don't seem to do that... I did leave the stock valve on. Also what did you paint your axles\calipers with?
Click to expand...


I think it could be fingernail polish.... I bet he used paint.
 
Did you try it with the stock prop valve to begin with? Always works for me. I keep trying to tell people to try it out, then change it if need be.
 
ipkyss said:
Did you try it with the stock prop valve to begin with? Always works for me. I keep trying to tell people to try it out, then change it if need be.
Click to expand...

Yeah, I had it like that for the first three months I had discs. It felt the same as having drum brakes...not much improvment until i swapped it out.

Indertdxj said:
What diffs do you have? I have seen mods for ford discs on rears (here in australia using Ford Falcon parts) but didn't know you could do a Grand swap?
Click to expand...

search for ZJ disc swap...I have the 8.25 rear
 
xjchris98 said:
So Andrew, when do you want to help me make the swap to discs?
Click to expand...

Whenever you want! It's so easy and really is a huge improvment...that should be your next mod, it only cost me around $50.

toysupra14 said:
mine don't seem to do that... I did leave the stock valve on. Also what did you paint your axles\calipers with?
Click to expand...

I painted the axles with black gloss rustoleum and the calipers were painted with some cheapo(krylon?) spray paint in a hurry and the calipers are still red after five months.
 
Just did this conversion, along w/ lift and bigger tires.

XJ prop valve works perfect, braking is far superior, No problems in the snow.

Best junkyard mod you can do for the money. As far as I know, Two friend of mine and I are the only jeepers in the CNY area w/ this mod. Anyone else?

Just my two cent's but I've had good results useing High temp engine paint, to paint brake calipers. Duplicolor makes like 25 different colors. good to 500 degrees or so.
 
Another person having great luck with crown vic discs in the rear and the stock proportioning valve.


I also concur, locking em up at 75 mph is a risky venture, irregardless of what you're driving!!!

In terms of figuring out which axle has more breaking....I was at a hockey game the other night and they drove a brand new TJ out onto the ice so that people could throw rubber pucks into it. When it got out there, it hit the brakes, the fronts locked up, but the rears kept going. I didn't get a close look but I would assume that it had rear drums, and obviously no ABS. Anyways, I only mention that because if you have a nice frozen lake near you, that might be a good way to see which tires get more braking power, and help you get the adjustment down.
 
Last edited:
I can lock up my rear stock drums. Are they too powerfull too? ;)
 
i have a Ford 8.8 with 31s still running the stock valve on my 1990...
and even at slow speeds the rear locks up before the front.

i don't know the difference in the actual caliper/rotor setup in the 8.8 compaired to the setups you guys have...

but i have this weird turn going down my street, it's a 3 way intersection going down a hill and i take a right at it, just outside the turn there's a speedbump, breaking IN the turn (where you would normally get back on the gas) for the bump always makes the rear end squeal a little like it's trying to lock up, but im going maybe 10-15mph

and i've locked everything up going straight in the rain, and the rears locked up completely, but i just slide in a straight line cause the fronts haven't locked up yet.....
so, since i slide straight, i've never been too concerned, but i always just figured the stock proportioning valve was why the rear locked up first...and the shytty stock booster on a 1990 is why the front WON'T lock up, haha
 
Of course your rear brakes even with drums are going to lock up first, because of the weight distribution shift from being over 2 axles all the way to the front, so at 75mph, you throw on the clampers and i'll bet you'll lock up the rear 100% of the time...my 2cents
Only 8 inches huh...we got over a foot on the weekend there...twas fun!
 
With mine in rain it seems as though if anything all wheels will lock up and I slide in a straight line whereas the other day it was dry pavement.

The fix would be to get an adjustable proportioning valve.
 
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