Lets Talk About OEM Brakes - Fade-a-Rama

[ed1948]

Just to show that the rear drums may not be a major problem....after the stops I could still touch the rear drums, the front disks radiated heat and the smell was strong.
I doubt that my driving style requires extreme brake performance but it would be reassuring that the stopping system has a good margin of additional safety. It appears the most cost effective short term solution would be to upgrade the friction materials. Thanks everyone for educating me.
I have never really experienced brake fade first hand. Even while doing aggressive repeated brake tests in my 96 Chev K1500 on the same stretch of road at higher velocity.

 

[pontiacgp]

Just to show that the rear drums may not be a major problem....after the stops I could still touch the rear drums, the front disks radiated heat and the smell was strong.

sounds like the rear brake are the problem. If the rear brakes are not doing their job it makes the front brakes work harder

 

[Injectedcutty]

sounds like the rear brake are the problem. If the rear brakes are not doing their job it makes the front brakes work harder

I'm wondering if he doesn't have the shoes adjusted out causing them to not grab properly???

 

[UNGN]

sounds like the rear brake are the problem. If the rear brakes are not doing their job it makes the front brakes work harder

This is probably true.

Turbo Buick guys know a lot about brake fade. Before we eventually give up and install a line lock, we relied on the rear brakes to hold 10 psi boost after a brake standing burn out. Boost holding ability of the rear brakes goes way down with heat. When they get real hot, 5 psi of boost can push locked front tires through the lights.

If the brakes are fading and the rears are cool, more rear brake will help.

 

[motorheadmike]

sounds like the rear brake are the problem. If the rear brakes are not doing their job it makes the front brakes work harder

Which is why you do not want to use the S10 wheel cylinders if frequent/hard braking is in the plans. They shift the brake bias to the rear, especially if you gut the prop valve. Those wheel cylinders were a bandaid for Turbo Buicks that wanted more holding capacity at the line while building boost (and losing vacuum assist), and were tied to the "long brake shoe" mods.

On top of what else has been offered I will add: use quality brake fluid. DOT 4 or better. ...and aluminum brake drums.

 

[ed1948]

I have adjusted the rear shoes as per the factory manual. I confirmed the adjuster functions. Before the brake test I did a number of hard reverse stops. I can feel the rears are on the verge of lockup during the panic stops which show no drifting.
Not knowing the history of this braking system I think the prudent next step is to renew the friction materials with upgraded goodies.
Done so far: bled hydraulics(clean and no bubbles), replaced flex lines, deglaze shoes and pads.

I also have to add that I have adjusted the parking brake cables for more free play - 6 clicks instead of 3. The PB will hold on an incline but will barely stop the moving car....Hmm, wonder if something's wrong with the rear setup. I never confirmed the shoes were oriented correctly. It's been over 20 years since I've dealt with rear drums and maybe I'm assuming too much.

 

[pagrunt]

Does it have the O.E. cast iron proportioning valve or was it replaced with an updated brass unit? My .02 would be looking at that.

 

[motorheadmike]

sounds like the rear brake are the problem. If the rear brakes are not doing their job it makes the front brakes work harder

Which is why you do not want to use the S10 wheel cylinders if frequent/hard braking is in the plans. They shift the brake bias to the rear, especially if you gut the prop valve.

On top of what else has been offered I will add: use quality brake fluid. DOT 4 or better.

Does it have the O.E. cast iron proportioning valve or was it replaced with an updated brass unit? My .02 would be looking at that.

Agreed. The cast iron one was recalled for a reason.

 

[UNGN]

Which is why you do not want to use the S10 wheel cylinders if frequent/hard braking is in the plans. They shift the brake bias to the rear, especially if you gut the prop valve.

You just have to run bigger tires in back until they stop looking up.

People said locking would be a problem on my buick with long shoes and S10 cylinders, but its hard to lock 275/60's. 215/65's might get a little hairy.

 

[clean8485]

I'm a bit curious about the recall for the proportioning valve. I was a dealer technician in several GM dealerships from 1990 to 2006. I did quite a few recall related repairs to both the A/G body cars for the rear backing plate/wheel cylinder problems, but I've never heard of a proportioning valve recall on these cars. I contacted 3 of the guys that I used to work with during that time, and they hadn't heard of it either. I've never seen a brass proportioning valve on any A/G body car that I've ever owned or worked on (and I've owned a few, and worked on quite a few, since they were first introduced). I have seen brass proportioning valves from time to time, but in my experience, they're usually an aftermarket part. I never saw one during the time I spent working at dealerships. Did this recall for the proportioning valve only occur in certain areas? Does anyone here have any information on it (recall number, vehicles that are affected, etc)?