TheMagikMan

I have an 86 Firebird TA with the WS6 package. I have the 9 bolt rear end and would like to keep it but have put quite a bit more power in it and am worried about stopping power. Right now I have 4 wheel disc with Delco calipers on the rear end and it appears that the previous owner rebuilt them less than a year ago. I did the stronger prop valve spring mod and it didn't help much, so I'm worried that I won't have the stopping power necessary to deal with almost 400hp. In dry conditions I can push the pedal as hard as I can and the car won't lock the tires up, and low speed stops take quite a bit of effort. I know it won't ever feel like a brand new car, but it should be able to lock up the tires if I put the pedal to the floor. I have done a fluid flush as well.

What are my options for brake upgrades that will fit under my 16" GTA style wheels? I know Wilwood makes a 4 piston kit for the front but they don't make one for the rear end. Baer makes a rear end kit but it's minimum $2500-$3000 for rears only. Are there maybe any Australian companies or ways to upgrade that will fit the Borg-Warner 9-bolt rear end?

QwkTrip

iTrader: (22)

I suggest calling BigBrakeUpgrade.com to talk through options. They know these 3rd gen F-bodies pretty darn well.

If they have brakes but don't have the right brackets available to adapt those brakes, then Kore3 will make you something (or already have it from a prior customer request).

LAFireboyd

iTrader: (3)

Not even the front brakes would lock up? They should've, at least. But if not, then you could be in for quite a surprise when you have working rear brakes.

The safe rear brake option for a 9-bolt, and by that, I mean guaranteed fit inside GTA wheels, is the 3rdgen Performance Package 11.6" PBR rear brakes. You'll find conversion parts/kits from Flynbye.com and probably Hawk's.
Flynbye Performance LLC
Hawks Motor Sports › 1982-2002 Camaro and Firebird Specialists

IMO, the best rear brake option for a 9-bolt is the Corvette C5/C6 rear brake conversion. You can get that conversion kit from Big Brake Upgrade. Scott created it specifically for me and my 9-bolt.
C6 Z06 Brakes; C6 Rear Brake Conversion, NEW from BBU: C6/C5 Std, C6 Z51, C6 Z06 - Third Generation F-Body Message Boards

However, the C5/C6 12" option has NOT been test fit with GTA wheels, only my 16" Formula wheels, so that's why the 3rdgen Performance Package brakes I mentioned first is the safer choice for GTA wheels. If C5/C6 12" rear brakes fit inside GTA wheels, it might require a 1/4" spacer, and it might also require LS1 rear calipers, which are interchangeable with C5 and C6 rear calipers. But LS1 calipers have a slightly shorter profile than C5/C6 calipers for more clearance inside the wheel. LS1 calipers are probably easier to find, and they're probably cheaper too. C5/C6 abutment brackets for the base brake option would be still required, not LS1 brackets.

I tried searching for a cheap used, even damaged GTA wheel to use as a test fit dummy, but I couldn't find one. If someone in the LA or Vegas areas has one, sees this and contacts me, I'll gladly test fit it.

The LS1 rear brake conversion isn't compatible with 9-bolts, only 10-bolts. It's also not versatile for any possible future changes, whereas the C5/C6 conversion is.

Another thing you'll have to address is the axle hardline for your current driver's side rear caliper. That hardline runs all the way into the caliper; no soft line was used between the caliper and the hardline. So you'll need a new hardline on that side for the 1989 3rdgen Performance Package option, regardless of which rear brake upgrade you choose. Sounds like a big deal, but it's not at all.

Abubaca

iTrader: (3)

Not to discount anything anyone here has said, but it's not the power that requires better brakes, but rather the speed! Are you planning on racing? If not, it's likely that it won't really be too much of an issue. Adding to that, you don't want the rear brakes to lock up, so they're purposely dialed down by the prop valve. Keeping that in mind, any rear brake can handle the clamping force needs. The real upgrade is the the brakes ability to handle repeated braking over and over and over, like in racing situations. If it were me, I'd ditch the delcos as they're a known weak spot. Beyond THAT however, I'd go with whatever system you can get your hands on and can afford. All options listed are good options. I've used the PBR/1LE brakes that LAFireboyd mentioned in TWO builds now, and they're easy to work on and readily available since they were used on both later thirdgens and early fourthgens. -and known to fit under GTA wheels. ....but there other options, as he mentioned. That C5/C6 combo looks pretty nice too! -though not sure if it fits the GTAs.

TheMagikMan

I don't necessarily plan on racing, but I do have some friends that I go on spirited mountain drives with, and if there's a deer or something in the road and a whole group has to panic stop, I don't want to rear end anyone. I have done the Grainger spring upgrade so my rear brakes should be better already but it hasn't done much. I'm wondering if I didn't properly flush the brakes or something.

TheMagikMan

Yeah the fronts won't even lock up. The entire braking system seems horribly weak. I have done all new rubber hoses, new brake booster, flushed the system, and put a stiffer spring into the prop valve for the rear bias.

Komet

Are you running semi-metallic pads? If you can't lock up the fronts, I'd start there before worrying about the rears. New AC Delco everything is very cheap.

Abubaca

iTrader: (3)

Those Delcos are known to seize up. ....you definitely want your brakes working right, and I think upgrading from the Delcos is a good idea. -But I agree with others that it sounds like there are other issues.

Denis.V

As far as I know, rear brakes of 2.000 Chevrolet Blazer 2WD are an option too.

You tube have a video about this option.

Neil350

iTrader: (1)

The later 9 bolt cars had a decent aluminum PBR set up, similar to what the LT1 4th gen cars had. If it's a delco moraine iron caliper, I would look at upgrading to that. The issue is going to be in the front brakes, an LS1 Fbody will fit under the stock 16s and provide better stopping power.

keithl1967

Checking in--the original poster is my son (his car, OUR project, lol). The issue really feels like it is a failing brake booster. Takes more force than it should to stop the car. We replaced the booster once already (I have another one coming--warranty replacement--in case we just got a bad new part from Cardone). I was shocked to see that the new booster ha sno adjustment in it...All previous boosters I had ever done required a measurement and adjustment ot make sure engagement was appropriate. This cardone (as well as the original removed) did not have any adjustment in the engagement pin to the master cylinder).

We also just upgraded the fronts with the Powerstop calipers, performance rotors (drilled/slotted) and ceramic metallic brake pads. That change really had no impact on the braking ability.

As stated, we have replaced all front brake components, all rubber lines around the entire car, front to rear hard line. Tried the spring upgrade for the prop valve as well. The rear calipers look brand new (sure they are remanufactured), and the prior owner confirmed they are new/rebuilt.

I've got a new master cylinder on the way to throw at it as well (may as well at this point). Only think I CAN'T find for it is a new/reman proportioning valve.

REALLY feels like a booster problem, though. But won't know until we replace it a second time for sure.

what are the odds we got a bad replacement booster?

1989karr

Ever find out?


Id say the chances are high... I got 2 bad reman boosters from NAPA for another car.....Im pretty sure cardone makes their remans as well.


.

keithl1967

ended up putting a new master cylinder on at the same time we put the warranty replacement booster on the car. car stops fine now, as it should.
We did also find that the seal on the cap of the original master must have been letting in some air, so I wonder if that was degrading the brake fluid as well. bled the brakes thoroughly after the master and booster install..

1989karr

Nice! glad it worked out!

keithl1967

yeah--one more thing to check off the list! LOL
I do think it was a bad booster (even though it was a reman)....

1989karr

my mother's Corolla had similar issues as your car... hers was the master..but with all these bad remans going around, it could have been the booster too! Or maybe a combo of both