Brakes

[sunburned]

I'm confused as to why a ZJ prop valve or even a liberty valve wouldn't work. They have very similar axles but with discs in the rear, so it should be an almost identical setup.

 

[EMSJEEP]

Removing the o-ring does not make the system 50/50. It just merges the two brake systems letting the fluid take the path of least resistance.

Which would theoretically be an even distribution.

The prop valve reduces the pressure to the rear, without the o-ring, it can't do that, given the previous reduction an open system would be closer to an even distribution than before.


The ZJ internals didn't seem to work. When I pulled the o-ring I could lock front and rear but the rear always spun forward...so if open is close to 50/50 and the ZJ is close to what...70/30...I need something in-between. Changing the internals from the stock to ZJ did squat.

...then in the meantime I think I lost either my MC or booster....

 

[sunburned]

Why not just swap over the entire ZJ block? Or try a liberty?

 

[Talyn]

Which would theoretically be an even distribution.

you would think, but that isn't how it works due to the fact that both systems are merged.

The prop valve reduces the pressure to the rear, without the o-ring, it can't do that, given the previous reduction an open system would be closer to an even distribution than before.

The factory prop valves are 50/50 until you do a panic stop, or create enough pressure in the system to compress the spring. Then it sends most of the pressure to the front brakes.

When I pulled the o-ring I could lock front and rear but the rear always spun forward...so if open is close to 50/50 and the ZJ is close to what...70/30...I need something in-between. Changing the internals from the stock to ZJ did squat.

How could it lock the front but not the rear if its 50/50? If you did a hard brake and you say its 50/50 open, then the rear should lock as well if not before the front.
You would need a, IIRC, weaker spring. That is if i remember correctly which circuit is the front and which is the rear on the prop valve.

 

[EMSJEEP]

you would think, but that isn't how it works due to the fact that both systems are merged.
The factory prop valves are 50/50 until you do a panic stop, or create enough pressure in the system to compress the spring. Then it sends most of the pressure to the front brakes.

How could it lock the front but not the rear if its 50/50? If you did a hard brake and you say its 50/50 open, then the rear should lock as well if not before the front.
You would need a, IIRC, weaker spring. That is if i remember correctly which circuit is the front and which is the rear on the prop valve.

I believe it was locking the rear, which is why I kept ending up sideways.

 

[EMSJEEP]

Why not just swap over the entire ZJ block? Or try a liberty?

Why would that be any different than changing the internal components?

I didn't do that initially because the bracket didn't fit around the larger MC. I sent it in to have the lines fabricated and it came back with a new block. The brakes still sucked until I pulled the o-ring. Then they were too good and then something else failed and they sucked again.

 

[Talyn]

Then they were too good and then something else failed and they sucked again.

They worked better than expected than something changed? Air in the lines maybe?

In your case (and what I intend to do in the future) is eliminate the stock prop valve completely, plumb the front open and then use a new adjustable prop valve on the rear. I don't know where your currently broken prop valve is, but I would put it under the hood, near where the stock valve is.

Have you done any math on your caliper pistons vs. stock ZJ setup? Some year ZJs with disc/disc use the same MC as the XJ (whichi s one reason I don't understand why SSBC thought you needed a new MC), and typically multi piston calipers need less fluid than a single piston caliper. Think piston area. If your brakes feel hard to you then your MC is too large, too soft and its probably too small... that is based on an otherwise working brake system.

 

[EMSJEEP]

They worked better than expected than something changed? Air in the lines maybe?

In your case (and what I intend to do in the future) is eliminate the stock prop valve completely, plumb the front open and then use a new adjustable prop valve on the rear. I don't know where your currently broken prop valve is, but I would put it under the hood, near where the stock valve is.

Have you done any math on your caliper pistons vs. stock ZJ setup? Some year ZJs with disc/disc use the same MC as the XJ (whichi s one reason I don't understand why SSBC thought you needed a new MC), and typically multi piston calipers need less fluid than a single piston caliper. Think piston area. If your brakes feel hard to you then your MC is too large, too soft and its probably too small... that is based on an otherwise working brake system.

I had the prop valve installed while I was at school, the local dealer gave me a good price for the work and happened to have a tech with a few built up jeeps who was available to work on it. I suggested putting it close to the MC, but he elected to put it halfway down the unibody rail on the common line to the rear. It basically had no effect other than to give me a soft pedal when it was open.

I tried running the new setup on the stock MC, it was a complete disaster and not being able to fab brake lines I had to have the shop down the street do the swap for me. The new, larger, MC helped alot. Then I started messing with the adjustments because it wasn't really good enough. I tried swapping internals but it didn't change anything. Then I pulled the o-ring and it was good, but too good. I then started searching for ways to drop the pressure to the rear a little but not as much as the stock or ZJ style prop valves. By the time I figured out that an SSBC in-line valve might help the brakes sort of sucked. At some point we replaced the booster with one of those cheap rebuilt silver colored ones which didn't really help. The pedal was relatively firm.

Then, at some point, I figured, well, maybe if I distribute some of the excess rear pressure back up front, it might work better...that didn't pan out...but I put the valve in at that point.

My idiot mechanic keeps bitching about how the rear pads don't slide right on those thin metal shims, but that has to be due to maybe a lack of grease and and a lack of actual pressure to move them.

My VANCO kit worked great on the fronts until I installed the SSBC kit, and I could stop pretty damn well even though the rear drums were constantly unserviceable and leaking.

 

[EMSJEEP]

Whatever, I ordered a Crown booster, I don't like that $75 POS rebuilt thing anyway. Before I do that I'll fix the SSBC prop valve and see if it will bleed. If nothing, I'll plumb around the stock valve, maybe replace the MC...I dunno...

 

[EMSJEEP]

Replaced the SSBC valve internals, looks like the old one was missing a piece. The new one gives me a firm pedal through the whole range, still no bite. Going to replace the booster next when it comes.

 

[AnarchyJet]

Do you have your rear calipers on correctly? The bleeder has to be at the top. I've seen upside down calipers cause problems exactly like what you are describing.

 

[Talyn]

One other thought, what pads are you using? Pads can make or break it. A lot of these high performance pads only do well when they are hot. You may want to take it out for a drive and really put some heat into the pads to see if that makes a difference.

 

[EMSJEEP]

Do you have your rear calipers on correctly? The bleeder has to be at the top. I've seen upside down calipers cause problems exactly like what you are describing.

I have two bleeders. The bolt that holds the soft line in place has a bleeder on it. There is another bleeder below that one. The calipers are installed with the parking brake spring facing up. I'm 99% sure that the calipers are on the right side...especially considering the system DID work at one point.

One other thought, what pads are you using? Pads can make or break it. A lot of these high performance pads only do well when they are hot. You may want to take it out for a drive and really put some heat into the pads to see if that makes a difference.

EBC Yellow Stuff pads. They work better when hot and broken in, but the pads alone wouldn't make it this bad. In fact, this is my third set of EBC yellow pads up front. The first set I (stupidly) wore down to the metal backing plates. The second set I replaced about half way through their wear life after I fractured a pad.


I swapped out the internals of the SSBC valve that froze and low and behold the new valve had a metal washer installed as a spacer. My valve was missing this piece. I swapped in the washer along with the new valve stem and gave it a good bleed. Now, regardless of valve position I have identical pedal feel. Someone is getting an angry phone call tomorrow...

I still have no pressure, and I pulled some really nasty looking fluid out of the right rear caliper. I'm pretty confident that this is a booster issue, at least in part. So, out with the A1Cardone rebuild and in with a new Crown booster tomorrow. After that, I want to pull apart the rear brake system and make sure everything is moving correctly, throw on some lubrication all around and hope for the best.

 

[Talyn]

I have two bleeders. The bolt that holds the soft line in place has a bleeder on it. There is another bleeder below that one. The calipers are installed with the parking brake spring facing up.

I am not familiar with the SSBC system, but usually you want the bleeder at the top of the caliper, above the line. That way, when you bleed, air an fluid will be forced in through the caliper, with the air going to the top and then out the bleeder. There is a bleeder on the soft line, but the problem I see with that is that when you bleed you will be forcing fluid/air through the lines, but not into the caliper and out. You could try to remove the caliper form the bracket, flip to the bottom bleeder is at the top and then bleed.

 

[EMSJEEP]

I am not familiar with the SSBC system, but usually you want the bleeder at the top of the caliper, above the line. That way, when you bleed, air an fluid will be forced in through the caliper, with the air going to the top and then out the bleeder. There is a bleeder on the soft line, but the problem I see with that is that when you bleed you will be forcing fluid/air through the lines, but not into the caliper and out. You could try to remove the caliper form the bracket, flip to the bottom bleeder is at the top and then bleed.

Apparently they have have different model numbers that end in "L" and "R" and I had those reversed. I flipped them. At this time I would like to extend my congratulations to the SSBC engineers and design team for using the most ancient parts to design a poorly engineered system that does noting it promises to do.

Using the calipers off of a '75 T-Bird dunno was quite possibly the most retarded decision ever. Instead of a straight piston you get a spiral and instead of modern pads that ride in shims you get some nice metal-on-metal action. If that isn't good enough, they used a system that requires that one take the whole damn caliper off to change the pads because those sliding bolts have a nut on the outboard side in a space to thin to get any normal wrench and it just turns and turns and turns from the other side.

Taking the whole caliper off would be easier if it were actually possible to get a socket on the lower bolt, but the space is too tight to even get the closed end of a wrench around the head of the bolt.

On top of that, when installed the correct way, which is apparently e-brake spring facing down, the D/S fixed cable is too short to make the run under the axle to snap into the bracket that I had to drill out to fit that terrible three barbed hook through.

The best part of my day was cross threading and then re tapping the threads on the two fixed bolts coming out of my new booster thanks to the pain in the ass and wholly unnecessary steel bracket holding the prop valve in place.

So...I have a new booster, new adjustable prop valve and I flipped the calipers. I ran out of brass crush washers for the caliper swap so I won't know anything until I replace those tomorrow and bleed it out. I also lubed up those rear calipers like a cheap date, so, they should slide at least half decent.

 

[Talyn]

I've heard complaints about the SSBC calipers before.

That lower bolt isn't any different that the ZJ brakes.. can't get a socket on it.. need to use a standard wrench.

Let us know how it works.

 

[EMSJEEP]

Caliper bolt sheard in half upon install...try to track one down tomorrow...or maybe SSBC will commission a replacement to be made by hand by a 6 year old indonesian child...

 

[Boostwerks.com]

By chance are these the caliper's SSBC used in your kit? There are two different variations with the 78+ Metric Caliper (pictured) and the earlier "midsize" caliper. Just curious.

If you need parts, I highly reccomend Speedway motors. They have everything for these GM calipers...
http://www.speedwaymotors.com/Street-Rod-Brakes.html

 

[Boostwerks.com]

I forgot to mention... The GM rear calipers require you to remove the caliper from the bracket to properlly bleed them as the bleeder screw won't be at the highest point.

More info...

http://static.speedwaymotors.com/pdf/910-31046.pdf

 

[EMSJEEP]

Those are not the calipers I have.

I know it's hard to tell from this picture, but they look like this:

...and they are stamped "SSBC"