John'89L98

Hey all... I'm once again trying to figure out how to get my '89 IROC to stop better than it does. I can't afford to go aftermarket right now, and quite frankly, I don't like the fact that I have to in order to stop.

My rear calipers won't stop the rear wheels when the car is raised in the air, and the brake pedal is applied. The calipers, pads, and hoses have been replaced. The hard lines have been blown out with air, the system has been bled 4-5 times so far with no change. I have the same exact problem with the Borg Warner posi rear in my '88 GTA convertible. Both my '86 and '88 IROCs have rear drums and they stop on a dime.

So, I'm wondering how many people have the same problem as me. How many folks have rear disk brakes on their cars that are practically useless? I'm wondering if it's time we sent a few letters off to GM threatening a class-action suit if they don't start admitting that they have a defective product out on the street.

Let me know if I'm alone in with this problem, or if this occurs as often as I believe it does. Thanks. - John '89 L98

Fire"Dutch"Bird

iTrader: (1)

GM offers a confersion kit for this problem,any dealer should know!

Tom Keliher

Did you buy your car brand new? Probably not....

Do you always set the parking brake every time you park your car?

The rear brakes are dependent on adjustment via the parking brake being set. If it is not, the rear brakes will not adjust up properly. After time, the pistons won't move past the point of the last adjustment and the rear brakes become ineffective.

Buy rebuilt rear calipers and start over.

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FORMULA 350 TK
Southern California 3rd Generation F-Body Organization©

[This message has been edited by Tom Keliher (edited October 09, 2000).]

JamesC

iTrader: (5)

There is a Technical Service Bulletin concerning rear discs. Regardless of ownership or mileage, if the car hasn't been repaired, GM is obliged (if I recalled correctly, this is only for manual trannies). I converted to disc. I use the handbrake on my 5 speed frequently, and I've never experienced a difficulty.

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TomP

Er, wait, his '89 IROC- doesn't that have the new PBR calipers and not the old-design units?


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-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards

BLACK Z

It should have the pbr calipers?

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86Z28, GM 350, Jet perf Q-jet & chip Dual snorkel air cleaner, Edelbrock performer intake, Edelbrock headers, Edelbrock cat-back, Off road pipe, MSD 6AL, Accel Super Coil, Taylor Spiro-pro wires, Rapid fire plugs, Jet fan switch, World class t-5, Hurst Short Throw Shifter, Ram Flywheel, Center force dual friction clutch,Aluminum drive shaft, BW disc rear 3.45's & a posi, PBR calipers, Earls braided brake lines, Polygrapite bushings all the way around, poly tranny mount & torque arm mount, Hotchkis lower control arms & panhard rod, Rancho limiter straps, KYB struts & shocks, Gm Wonderbar, Edelbrock strut tower brace, SSM sub frame connectors, Jamex lowering springs, Carbon metallic brake pads, Crossed drilled rotors, Mobil 1 Tranny fluid & motor oil, GM syntheic rear end oil, K&N, Grant stering wheel, 1,200 watt system, Jet Black Paint, 91 Z28 rims, 92 wing, Tinted windows.

ws6transam

The recall you describe only applies to 1982-1988 calipers with the screw-type parking brake lever. The 1989-up rear disks are aluminum PBR calipers with eleven inch rotors. they have no recalls AFAIK.

My brand-new PBR braking system, as purchased through GM, does the same thing. I upgraded from the old-style brakes, you see. I was worried as well, but I've since come to the conclusion that they do indeed work on the street as evidenced by the rear wheel lockup I experienced at Gingerman Raceway last year. The reason there is so little brake bias is, I believe, due to the majority of the weight being transferred to the front brakes in a hard braking maneuver. GM made the rears lightly biased to keep you from swapping ends (via uncontrolled oversteer) when you jam on the brakes in a turn on a road course. When I'm using road race tires, these brakes dust up, heat up, and grab like thief. However, when I place the car on jackstands, it takes all I can give to keep the rear wheels from rolling after a few seconds. The brakes seem to grab, then let off after a second or so; almost like pressure is bleeding off into the front braking circuit... I just shrug, and remember that they seem like they are working well on the race course!

blowen90ta

yes,i'm the origional owner--i bought my car off the showroom floor in 1991 as i like the older ta ground effects .and since then i have had the breaks checked out by 7 dealers and talked to 2 factory service reps to no avail.the final soulition offered was a trade up to an abs car what bull$hit mine are the same as you have described very little to no breaking force good thing i'd paid extra for four wheel disks--what a ripoff,i think that the only solution is to modify the prop valve to let full pressure through then add an ajustable valve to the rear lines--that will be my winter project.anyone else have any thoughts on this?

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1990 Trans Am,350 TPI(L98),WS6suspension ,bridgestone RE71's /245/45/zr16
paxton supercharger, alston sfc's,msd 6AL-BTM,
8.5 superconductor wires SLP 1-3/4 headers,duel cats,3"slp exaust, lakewood LCA's,T.B.Bypass
160 degree stat,alum driveshaft,fiberglass wing, secret mods

"if you cant win fair CHEAT"

Christobal

90ta

I will agree the iron rear calipers from 82-88 are more of a pain than they ought to be.

If you were to gut the combination valve and install an adjustable proportioning valve, assuming everything else is OK, you'll probably get that nice extremely firm pedal and solid pressure to the rear. I was involved in converting a 91 with drum rears over to Baers on all 4 corners. It ended up perfect in my opinion.

On my 88 GTA with recently replaced calipers in the back and new master, braided lines everywhere possible including from the single line down the chassis to the T junction. Bled numerous times in all different manners. The pedal is still somewhat "mushy".

I'm gutting the combo, installing the adjustable and putting on the pbr rears in the near future. Should be solid at that point.

merf23

Can front calipers be put on the rear? Obviously the parking break would not work but that would be a good compromise IMHO to have rear brakes that function properly. Just curious if anyone ever tried this and what the results are.

John'89L98

Well, with my IROC being an '89, the recall doesn't affect it. Of course, I'll look into it for my '88 GTA. Since there seems to be very little I can do besides change the rears out for rebuilt ones, I guess I'll have to do just that.

As for the prop valve, I guess I can see why only 30% is sent to the rears, but 30% should be able to at least stop the wheels from moving while the car's up on jack stands. There's no excuse for that. None.

GM should never have put a product on the road that has to be worked a certain way before it will work when it needs to. In other words, I don't see why it should be necessary for one to use the handbrake in order for the calipers to work properly. It's a poor design, and it should be addressed.

I sent a complaint to the NHTSA concerning the rear brake problem I have. I would suggest that anyone else that has, or has had this problem in the past, do the same. Who knows, maybe with enough complaints, GM will be forced to do something. - John '89 L98

farm-kid/88camaro

I just swapped to a disc rear and have went through hell trying to get it to work. I have replaced master, prop valve and two rebuilt calipers on the back plus new rubber lines. The calipers will still not hold tires when raised off the ground. Im pretty much fed up, i hope we find a solution

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________________________
88'Camaro
305 TBI

355 IROC-Z

i have always wondered why my car never stopped for sh*t. GM did what i figured, had more bias for the front for the average driver, easier to control a push then swapping ends. as a road racer myself, i know you want your fronts to lock up a split second before the rear, unless it is a wet surface. too much rear will make your you swap ends, like somebody has already mentioned. i found that out the hard way at charlotte in my enduro kart, that concrete looks pretty damn hard.
exactly what is replaced in the recall, or fixed. do you actually get the non-bitch calipers, hehe. take ur easy

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87 iroc-z 355 TPI 5 spd. 51006 SLP cam adv. 4* (106.5* centerline)
hypertech stage II chip/ 160* stat./ Airfoil, accel AFPR
3.45 rear (stock)
Flowmaster, K&N w/ hacked airbox
14.38@100mph 2.2 60'
removed MAF screens

TomP

Dan's (ws6transam's) page has the recall info at the bottom- http://www.isthq.com/~dan/1LEbrake.html

I checked prices on the "revised" actuators (pistons)- GM wanted $100 each for them. You'd think a recall item would be cheaper, eh?


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-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards

DSouthern

I have had problems with my emergency brake working ever since I bought my 87 GTA a couple years ago. As far as I can tell the rear brakes are working, they stop the rear wheels from spinning when the rear is up on jack stands.
I was thinking about getting a couple rebuild calipers to correct the emergency brake problem. Should I look for a particular brand of rebuild or will any Kragen's, Pep Boys, auto parts place do?

BLACK Z

I would go with gm part's.

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86Z28, GM 350, Jet perf Q-jet & chip Dual snorkel air cleaner, Edelbrock performer intake, Edelbrock headers, Edelbrock cat-back, Off road pipe, MSD 6AL, Accel Super Coil, Taylor Spiro-pro wires, Rapid fire plugs, Jet fan switch, World class t-5, Hurst Short Throw Shifter, Ram Flywheel, Center force dual friction clutch,Aluminum drive shaft, BW disc rear 3.45's & a posi, PBR calipers, Earls braided brake lines, Polygrapite bushings all the way around, poly tranny mount & torque arm mount, Hotchkis lower control arms & panhard rod, Rancho limiter straps, KYB struts & shocks, Gm Wonderbar, Edelbrock strut tower brace, SSM sub frame connectors, Jamex lowering springs, Carbon metallic brake pads, Crossed drilled rotors, Mobil 1 Tranny fluid & motor oil, GM syntheic rear end oil, K&N, Grant stering wheel, 1,200 watt system, Jet Black Paint, 91 Z28 rims, 92 wing, Tinted windows.