Brake performance question.

[Zurbo]

Recently I've completed a full rebuild of the disc / drum braking system minus the lines which checked out fine.

I've replaced the master cylinder last month since it croaked.
Over the holidays I went ahead and attacked the rest of the system with new calipers, rotors, wheel bearings, semi-metallic pads, new slaves, semi metallic shoes, and turned the drums.
All four brakes are working with a real good stiff pedal but I feel they are not performing wery well.

Since these are power brakes, I would expect to be able to lock them up once I stood hard enough on the pedal. The power assist seems to be working and I can lock 'em up on a gravel road but not on dry pavement.

Maybe I'm too used to my "other" Chevy. They are working somewhat better than before but I guess I was expecting a night and day difference since the old pads and shoes were not semi-metallic and just about shot.

As far as tires, I am only running 255 70 R15's so it's not like i'm trying to stop a monster with 44" swamper tires.

To me it just feels like the brakes just aren't performing good enough. When it's running on the high idle circuit in the cold mornings it actually feels like it's not going to stop at all so I'm constantly throwing it in neutral which is getting old.

So I'd figure I'd ask and see if it is normal to not be able to lock up the wheels on these trucks.

Thanks!

[Longhorn Man]

Well, mine are hard to lock up...but I know my brakes are crap.
We actually refer to mine as delayers.

[68 Suburban]

Make sure your rear brakes are making contact. I had a 92 chevy van that I was always wondering why it was still moving when I stoped on snow or ice. The star wheel on the rear drums was frozen, so the truck was only stopping with the front disc. Now I know why I was getting 6000 miles on the pads in Front. Once I unfroze the the star adjuster, the truck was fine after that.

[BUXMAN66]

best advice i know is to make sure you don't have air in your lines.re-bleed 'em and make doubly sure.i'm personally not too fond of the semi-mettalic pads/shoes,imo all they do is chew up your rotors and or drums.sorry i can't help more.hopefully there's no water in your lines,also.

[jku72]

I had this happen, turned out there are several sizes for the same year on mastercylinders, they are sized according to what your brakes are. I suggest going to a smaller bore master, so that you get a lot more force. It makes a big difference to go from 1.25" to a 1". The best bet is to call some aftermarket brake expert gurus who can probably help you a lot more than I ever could.
In short, be sure your master cylinder matches your components. Makes a world of difference.

[Southpa]

I went thru similar when I swapped my front end for the front disc setup. Pretty much new everything, including front lines, but was still not getting that pedal sensitivity that comes w/ discs. Replaced the booster and that was the solution.

[Zurbo]

Thanks for the tips guys!

I'll doublecheck the rear brake adjusters, make sure the new master is the correct size, run another quart of fluid through the system, and have the booster checked out.

[Zurbo]

Rear brake adjusters were fine and I tightened them up a half turn so the drums would barely fit on, the booster is working fine, but the master cylinder still bothers me. I got it from AutoZone and it has equal size reservoirs for both the front and rear where my factory one was definitely different sizes for the front and rear. It's like it is for drum brakes. They looked it up again and they gave me the right one for a 72 according to their books. We looked one up a 73 for grins and giggles and it looks correct. It has two different size reservoirs like my original. I’m going to try it instead and hope for the best.

[bigvinnie]

can't say I've ever seen a disk brake master cylinder for these trucks that had equal size front/rear reservoirs.... front is usually bigger than the rear..

[Zurbo]

I'm pretty sure Autozone has the wrong master cylinder for my truck...

Found a few piccy's.

Here is the original.

[Zurbo]

This is what they first sold me.

[Zurbo]

And this is what the current one looks like. But it is for a 73.

[Zurbo]

One BIG problem...

It seems the correct master cylinder does not use the same length push rod. I estimate that the new one needs to be an inch shorter.

Do they make these as seperate parts?

[Zurbo]

After some more research I have found two additional master cylinders to try. One is a Delco/morane and the other is a Bendix. They normally don't stock them at ANY parts store here in Wichita so of course I have to wait 'till Tuesday. Hopefully one of these work and also make the brakes work better.