Sorry- another rear disc brake question

[350runner]

Thank you for documenting this. Most don't document when things go wrong. I had this as one on the list of things to do, so seeing headaches ahead of time really helps to plan ahead. Thanks!

Sent from the dust in front of you!

 

[77 K20]

As far as the one brake that was dragging.... the outside pad was firmly pressed up against the rotor. I ordered some shim washers thru Amazon and was able to install them without taking whole truck apart. Just raised it up, removed the tire/wheel and then loosened up all 4 bolts on the axle tube that bolt on the brake bracket. This had to be done with a long wrench (couldn't get a socket and ratchet in there). It was hard to break them loose since I used locktight and lock washers on them. Once all 4 were loose I removed one bolt at a time and slid washers between the bracket and the axle tube to space the bracket out a bit. 2 washers stacked did the job. There was equal space between both brake pads and the rotor. I was then able to spin the rotor by hand with it up in the air. Even after pumping the brakes I could still spin the rotor by hand.

http://www.amazon.com/gp/product/B004K1FFZK/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1

I also ordered some adapters for the brake lines. I didn't like how I had to reverse the brake lines on that new master cylinder. I'd read online that some say it doesn't matter. Others say it did.... don't know. I did read that the primary circuit is often for the front brakes- and the reason for that is the pin that is out of the brake booster will push directly on the primary circuit piston. The secondary piston is separated by a pocket of brake fluid. In theory if the seals in the piston fail, the secondarys may not work, or might work slower. And if you don't have rear brakes that isn't quite as big of a deal.

So with that in mind, I swapped the lines back to how they were on my original master cylinder. That took me most of the day- as I had issues. One of the adapters was wrong, got stuck in road construction, had problems finding a new one... blah blah blah....

Since that took so long I didn't install the adjustable proportion valve yet. But the brakes are now better balanced than before. The type of stop I did before on pavement that resulted in rear brake lockup didn't happen with the lines moved back. I went on a 6 hour drive up a long dirt road almost to Canada and I can get the rear brakes to lock up on gravel, but had to hit the brakes firmly. Hopefully by the end of this week I can get time to put in the adjustable proportion valve.

 

[77 K20]

Another update....

Even with shimming out the brake bracket so the rotor is centered between the brake pads the brake is still heating up. After just a short 5 mile drive the problem brake was at 165* and the other brake was at 70*. It looks like since the caliper guide bolts did not want to bolt up (they go thru the bracket at an angle, and won't go thru the holes on the outer side of the bracket without prying them into position with a screwdriver) that the caliper is binding up and not floating like it should be.

I contacted DIY4X and he said the holes are straight for the caliper guide bolts, more than likely one of the brake "ears" was tweaked a bit. I'm guessing this is a good possibility with the design as there are 2 bends, then they weld in some extra support. Any/all of that can warp or bend the bracket. He said for me to send the one bad one back, then he'll send out a replacement.

It took 10 days last time from order to when I had it in my hands. For me to ship it out and for him to get it, then send a replacement would then take at LEAST 2 weeks. I need the truck to set up hunting camp next week. Tried to call and email him, but no response. So I used their website to order another set. Under comments I put ONLY NEED 1 to fix dragging brake issue. Ship ASAP. I'll see what happens.

Looking back I should have just ordered the brackets from ORD. They are flat metal with a spacer. Not much can go wrong with that.

Work is sending me out of state for the next few days- so no work will be done on the truck.

This project has been a pain....

 

[77 K20]

I got my new brake bracket yesterday and installed it. The old one was definitely bad. Somehow it looks like it was twisted a bit. That is one possible problem with using this style of bracket. By the time they bend it, then weld in the reinforcement it can warp.

If I ever did this again I'd just get the straight ones from ORD.

 

[Green79Scottsdale]

Updates? How is it working for you?

 

[77 K20]

For normal day to day driving it feels fine. If I have to hit the brakes hard on a gravel road the rear tires lock up. Haven't tried a hard stop on pavement, but suspect the rears would lock up there also. Also haven't tried driving in snow yet. That might be bad.

Once again I'm not sure how to add the adjustable proportional valve. I called Baer themselves and asked how to install it. They said having 2 proportional valves in line with each other is "bad, and can do bad things". He said simply "gut the existing combination valve" and it would then work properly.

Doesn't seem to be that easy. Even if I "gut" it I can't add the adjustable prop valve between the MC and the combination valve. If I do, then I'll get a brake warning light on in the dash as there will be a difference in pressure front to rear, and it will trigger the light.

I looked up how to gut the combination valve... the stock one seems easy. I now have an aftermarket one. Seems most are built differently. Instead of a spring and rod inside that could be removed they are built into the nut. Didn't see a way to take it apart. Contacted Just Right who made the brake combination valve. They said they don't know how to disable the proportional part of it- but they said they would just add the adjustable valve between the combination valve and the rear axle. That would make adjusting it a pain in the butt.

Still thinking of what would be best.

 

[Green79Scottsdale]

Don't you just replace the combination valve with the adjustable valve? Doesn't the combination valve effectively split up the front and rear brake systems? That is where you want the adjustable valve. Pull the bulb out of the dash, it won't bother you that way!

 

[77 K20]

Don't you just replace the combination valve with the adjustable valve? Doesn't the combination valve effectively split up the front and rear brake systems? That is where you want the adjustable valve. Pull the bulb out of the dash, it won't bother you that way!

The factory combination valve does 3 things. Part of it separates the front and rear and also provides a warning in case of a loss of pressure. The next part is a proportioning section for the rear brakes. Then there is a metering valve for the front brakes.

I haven't seen any adjustable proportion valves that were a direct replacement for the factory style combination valve. I didn't feel like re-doing all the metal lines in the whole truck. I'm whining I know... but I hated replacing the stock one for the disc/disc fixed one to begin with. I had to remove my ORD steering brace then remove the 5 lines. Then I got showered with brake fluid that dripped everywhere. I had some problems getting the lines to thread properly and not cross-thread. This was why even if I did find an adjustable one for the factory location I didn't think it would work well... the steering brace covers it. I might not be able to get in there to adjust it easily.

The factory one has 2 inlets, and 3 outlets. The adjustable one I bought is just one inlet, one outlet. It was for the rear brakes only. They do make some with 2 inlets and 3 outlets but the inlet/outlet locations are different.

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vs this:

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[77 K20]

I started looking for pictures showing how the ORD steering brace covers the combination valve. Found one:

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In doing so, I also found another picture:

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Someone here bought some fittings.... one is a T fitting to tie the front 3 lines together, and then a union to tie the 2 lines for the rear together.


I was hoping to keep the warning light originally. If I ever did get a leak in the system I'd like to know before I lost 1/2 my brakes. On some of the roads or trails I have been on a failure like that would have been catastrophic. It shouldn't happen... I did replace all my soft brakelines with the braided stainless and kevlar version.

 

[77 K20]

It recently started snowing here- and it is the nice wet type of snow that is excellent for making snowballs. It packs down at the slightest touch and then gets very slippery. I've found out that by barely hitting the brakes the rear tires immediately lock up, and the truck then starts fishtailing. Something had to be done...

So I called the Right Stuff Brake Company and explained what I had going on. They said it was fine to have the disc/disc combination valve and then mount the adjustable proportion valve AFTER it but before the axle. The only place to have it accessible then was the front crossmember. The way it is mounted I can easily reach under the bumper and adjust it. The knob actually slightly hangs below the crossmember for easy access.

I had to adjust it almost all the way out (choking down the rear brakes) almost all the way before I finally got my front brakes to lock up. (NOTE: Fully adjusted down still gives you something like 52% of brake power to the rear. Wide open on it gives you 90%)

It is still snowing and I've spent the day driving all over the valley. So far, so good, and I'm happy.

In this picture I wasn't done yet. I still needed to re-attach the brake line bracket on the frame and I still need to drill a hole thru the crossmember and bolt the adjustable proportion valve down.

 

[MadOgre]

How much was the valve? Where did you get it? I actually was thinking about that the other day and for the life of me could not figure out why there would be any issue in simply reducing the rear pressure just like you did. I was thinking about mounting a valve just before it goes down to the rear axle.

 

[77 K20]

How much was the valve? Where did you get it? I actually was thinking about that the other day and for the life of me could not figure out why there would be any issue in simply reducing the rear pressure just like you did. I was thinking about mounting a valve just before it goes down to the rear axle.

It was about $50 and I got it from Summit Racing.

I spent a few minutes trying to figure out where would be the best place. I almost put it closer to the rear axle, but on the day I installed it the weather was a sloppy mess. Snow was melting and the truck was dripping all over. Crawling under the rear to get it dialed in would have made me soaked. Up front things were much easier to get to and I was able to stay dry except for one knee.

I spent the day out in deep snow hunting with my father in law and my brother in law. It got up to 45* so the snow was wet and heavy and would turn to almost like ice when you drive over and pack it. Some of the roads were too steep to even climb. I didn't have any problems coming down them (at least I didn't have the rears lock up immediately).

 

[bucket]

About the front/rear circuits at the master cylinder. I think it is best to just put the lines into the cylinder how they fit without adapters, because I think GM intended it that way. I have a lot of GM vehicles with various brake setups and went looking at the master cylinders one day out of curiosity. A lot of them actually had the front brakes run to the front of the cylinder, while others had them run to the rear of the cylinder.

In doing so, I also found another picture:

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Someone here bought some fittings.... one is a T fitting to tie the front 3 lines together, and then a union to tie the 2 lines for the rear together.

That's actually the factory line setup on a '90-'91 with rear ABS. My '90 was just like that, although someone had removed the ASB stuff up at the master cylinder, and had an adjustable valve on the rear circuit.

 

[Green79Scottsdale]

That's a good picture of the ORD steering brace too.

 

[Rusty Nail]

Is this thread over?
Total cost?

Recommended? Would you do it again and if so, what would you do different?
How could one improve upon your efforts?
Whew! That's a lot of questions but I feel like you kind of left us hanging...