Anyone else have problems getting their 11.6" PBR's to hold the rear wheels on jackstands?

Here's a list of everything I've tried so far.....
Replaced rubber hoses with braided stainless.
Vacuum bled system.
"Buddy" bled system.
Replaced rear rotors and rebuilt calipers. (bled again)
Tried replacing master cylinder (bench bled then vacuum bled system again).
Tested vacuum booster. Held vacuum very well...even overnight.
Assumed my engine didn't make enough vacuum (8" at idle), so I installed reserve canister. One way check valves working properly and holding vacuum.

Even after all of this, there was no change. The brakes would barely stop, therefore, I opted to replace the combo valve with aftermarket adjustable prop. valve.

Still no change, so thinking there must be a restriction, I replaced every line on the entire car front and rear. Installed Hawk HPS pads all the way around...

Still no change...well, a little better, but they still suck!

Having exhausted every other possibility I could think of, I deleted all vacuum assist and installed a manual master and changed the pedal ratio to 7.3:1. Reinforcing the firewall and the whole bit...The new master is a 1" bore dodge style master.

The brakes now are stopping on jackstands, but any throttle AT ALL in gear will cause the brakes to slip.

The front brakes will lock up if I try hard enough, so I tried swapping lines from front of master to rear. Still no rear stopping power.

While "buddy" bleeding, the front bleeders spray like a pressure washer. The rears are more like a 2-beer ****. Vigorouus, but nothing special, LOL.

I'm at my witt's end. is there something I'm forgetting to do?

Should I have used a smaller 3/16 line instead of the 1/4 from the prop. valve to the rear axle?

Do I need a larger bore master?

Do I really need multiple piston calipers to hold the rear wheels under a load?

 

Try adjusting the free travel.

https://www.thirdgen.org/forums/susp...ear-brake.html

JamesC

 

Thanks for replying.
I adjusted the free travel with the tiny allen screw, but it seems to have no effect.

I do not have emergency cables or cable brackets on these calipers. Is that the whole problem?

Will a regular GM metric caliper mount in place of the PBR's?

 

The metric GM calipers have a much larger piston and swept pad area.

Has anyone successfully adapted this caliper to their rear end?

Do the early 3rd gen disc rears have the bracket needed for this?

 

If you're talking about the Delco-Moraine iron calipers, 82-88, then they will fit 89+ axle flanges; however, you'll need to swap rotors, calipers and backing plates (as well as the proportioning valve and e-brake cables).

JamesC

 

i swaped out mine for LS1 brakes all the way around and they suck sound about as good as yours

 

this is you problem. try put something to emergency cable mounting point on caliper end on\release hand brake few time. I have same problem as you .and when i on\off handbrake on caliper manyaly they start brake . sorry for bad english

 

I just ordered a pair of brackets that will allow a normal front metric caliper to be bolted to the rear axle flange. (about $50 delivered). No emergency brake mechanism to worry about.

I should have something rigged up in a week or so.

If it works better than the PBR's, I'll let everyone know.

 

This was/is the problem on the Delco-Moraine calipers, 82-88 or so, but shouldn't effect 89+ PBR's.

JamesC

 

i just ordered my drum rear conversion brackets from edmiller...these brackets will allow me to bolt these on to my 10 bolt drum rear and install my 89-92 aluminium pbr calipers with 11.6' discs at the back ..i have all new hoses and prop valve for 4 wheel discs...i have been reading these posts here,,now i 'm kind of discouraged,,,are these brakes worth the swap from my disc/drum combination now?..my car brakes fine and the e-brake cable is perfect with the drums..so should i install these rear discs system or do i need to spend big bucks for the conversion kits out there?...thanks...

 

The situation may be that you/we only hear about the occasional problem with the brakes and not the success stories. I swapped without any difficulties--and I suggest that many others have as well.

JamesC

 

ok thanks for the encouragement...you installed these pbr brakes on a drum rear?..anything i should look out for?..ed says to install 1995 rear rotors(4th gen) if the 89-92 rotors don't fit properly on the axle drum shafts....anthing else to look out for?..thanks.

 

No, I swapped disc to disc.

JamesC

 

i second that-my pbr's (front and rear) work great.

 

i guess i have a similar problem with my pbr's, ithey don't seem to work very well if is wet out or a little slick when i hit the brakes the front tires lock up and the rear wheels keep pushing the car or the rear tires keep spinning after i'm stopped, it's like i don't have rear brakes at all. when i swapped the rear in my car i changed the p valve but not the master cyl could this be my trouble???

 

Under normal circumstance, no.

JamesC

 

UPDATE

Ok. Installed 2.75" bore (oversized) metric calipers and brackets on the rear axle.
I got the brackets through a circle track place for 20 each.
I got the calipers loaded with hardware for 60 each.
Brake pads were hanging over the outer edge of the rotors about 1/4", so I ordered 12" brake rotors (slotted/drilled). Now everything fit pretty well, but had some slight fitment issues with the right caliper slider bolt, so I had to readjust the bracket and bolt back into place. I tack welded it for safety's sake and took it out for a drive.

They can lock up easily now, so I guess that adjustable prop. valve will be of some use.

Guess the swap cost about 325-330 including gear oil and new axle seals.

 

I guess the only MAJOR downside to this swap is the necessity to buy large rims. The small 15" rims wouldn't clear the calipers. I put some used 16" rims on to test the brakes.
They fit well and the rotors filled them up nicely.

 

im gonna create a new post on something i found tonight while overhaulin my rears.....it seems as the banjo bolt "hole" and the "hole" in the actual brake line were offset "left to right" from eachother. meaning the last person (or maybe GM...cause these look olllllld) to mess with my brake lines needed to "flip" the brake line banjo end around and then bolt it to the caliper. I'm trying to work on some pics b/c not sure if im being clear. my brake line did not like it when i flipped that head around to mount to camiper b/c they were so used to being on the one way i guess....it just binded up and was funky, but that caliper bled like it never bled before!