Could 4 wheel disc brakes really be this weak? - Third Generation F-Body Message Boards

ZZ3Astro · 07-05-2009, 01:01 PM

I have an 87 Iroc with 4 wheel disc brakes. The braking has been poor since I got this car. I've been looking through pages of posts on this board and I see a lot of LS1 brake upgrades. I've seen other people post about being unable to lock up the wheels but the threads end without a solution.

Years ago I had an 86 sport coupe - for a time with no rear brakes - and it did a better job stopping the car with skinnies than the Iroc does with big tires up front. Even before the skinnies, I can remember countless times of pushing locked front tires while stalling up to launch.

Anyway, I just upgraded to Green Stuff pads up front. While they do feel more grabby, I still cannot get any wheels to lock no matter how hard I stand on the pedal. I've done all the tests on the vacuum booster and it seems to be working (not to mention a huge difference from no vacuum). I've replaced all rubber lines. There are no leaks in the system. Everything seems to be in order, but I sure wouldn't want someone to pull out in front of me and stop.

So my question is to those with 4 wheel disc brakes, can you make your stock brakes lock up your tires if you stomp them hard enough? Is the final word that they just suck and need to be upgraded to LS1 hardware? Thanks for any ideas.

steve

84 1LE · 07-05-2009, 01:43 PM

The stock 10.5 dia/cast iron caliper set-up certainly isnt as good as a 1LE/Ls1 upgrade, but why do you want to be able to lock the brakes up.Locking your brakes doesnt improve stopping distance.You could have air in the master cylinder!Maybe bleed it first, then the rest of the brakes.Maybe the prop valve is bad!Resurface the rotors!Im sure there are more factors, but being able to lock the brakes up is no indicator of a properly functioning brake system though.

BlueIroc-Z · 07-07-2009, 11:18 AM

I just took my IROC out the other day and was doing some hard stops. Mine has the same issue. Requires way too much pedal pressure to get anywhere near a quick stop, and no lock-up. I haven't done any diagnostics on it yet 'cause there's other things that need to be done first (like tabs maybe

). I'll subscribe here for now to see what happens with yours. When I get around to it, I'll post up my progress. (Don't hold your breath, it'll be at least a month...)

Also, @ 84 1LE, we don't necessarily "want" to lock our brakes up. I think what we are doing is assuming that there should be more than enough braking power available to lock-up the tires, and because it won't lock-up just makes it seem like something is wrong resulting in this loss of braking power. That and, in my case anyway, a quick controlled stop from 50ish MPH in my IROC seems to take way too much pedal pressure. By comparison, I am exponentially more confident with the feel and operation of the disc-drum setup in my 1991 Dodge Dynasty (basically a Chrysler New Yorker) and that just seems wrong.

Stephen · 07-07-2009, 12:31 PM

A good working brake system, pre-ABS, should have enough pressure to lock them up. ABS will shorter braking distance, but that is a different matter altogether.

My 87s did at 65mph, just before I hit the deer, a few years ago. The only thing I know about my brakes, is are they are stock calipers & rotors, with Hawk's pads (now discontinued by Hawks) & braided caliper lines.

Rotor wear is good & the amount of brale pad I still have is good, but they are bone stock 87s.

Not very helpful in solving your problem, but lets you know that yes....The stock ones SHOULD be able to.

But putting on braided lines could be one step towards helping, especially if your 22 yr old stock rubber lines are bulging any, when braking.

zride91 · 07-07-2009, 01:12 PM

Probably not the case, but I figured I'd share any way just incase it sparked something...

I was trouble shooting something under the hood, and when I went to take it for a test drive afterwards, I was STANDING on the brake pedal to make it stop. After I took a look, I realized I forgot to reconnect the vacuum line that connects the brake booster to the rear of the intake. Maybe check for leaks in the vacuum line, with the line completely disconnected, it's FREKIN' SCARRY!!

84 1LE · 07-07-2009, 01:29 PM

Sometimes a hard pedal is usually the result of a bad diaphram(in the booster)or a bad master(internal wear/leak).

HarmonyCamaro · 08-29-2009, 01:11 AM

i have 4 disc breaks and i tested it out today for some odd reason and it locked the fronts only not the rears lol also have a 83 camaro

1970 Buick · 09-07-2009, 09:12 PM

I have the same problem with my breaks. I pulled the wheels and checked the rotors and pads. All look good. I cannot lock my fronts up enough to do a burnout at the track. They stop pretty good in traffic , but smoking the tires is impossible. I checked the vacuum line and that was fine. Fluid is fine, but I am going to check the master cylinder next. Let me know what you find out. Good luck!

Stephen · 09-07-2009, 09:17 PM

Quote:

Originally Posted by 1970 Buick

I have the same problem with my breaks. I pulled the wheels and checked the rotors and pads. All look good. I cannot lock my fronts up enough to do a burnout at the track. They stop pretty good in traffic , but smoking the tires is impossible. I checked the vacuum line and that was fine. Fluid is fine, but I am going to check the master cylinder next. Let me know what you find out. Good luck!

Your 89 GTA has totally different rear rotors & calipers than the OP. Yours SHOULD be better. Larger rotors & better calipers.

1970 Buick · 09-07-2009, 09:26 PM

Yea, I am not sure why mine seem so weak. Last summer I could do a burnout forever. After all the mods I have put on this summer, it pushes right through the brakes. I want to get it figured out before the 16th, that is the last night of racing at our local track. I want to be able to atleast heat the new drag radials up a bit.

1970 Buick · 09-08-2009, 10:57 PM

WSell, my mechanic told me today that my brake problem was due to a vacuum leak. So, hopefully that will be fixed by tomorrow. Let ya know exactly what it is soon.

1970 Buick · 09-10-2009, 08:43 AM

There was a leak in one of my runners that was causing a serious vacuum issue. Once that was fixed, the breaks work great! Good luck to anyone else having stopping issues.

madmax · 09-10-2009, 01:00 PM

Check for leaks. Replace the rubber hoses. Bleed the brakes, air is a terrible replacement for brake fluid. If none of that solves it, time for a new master and/or booster.