This weekend I finally finished my rear swap and while it was apart I rebuilt my rear suspension and drum brakes.

During the brake rebuild I used a Praise Dyno kit (http://www.praisedynobrake.com/bib.htm), which uses ceramic shoes, stiffer return springs and what they call "High Volume Wheel Cylinders for less pedal pressure", along with all the other new hardware.

Other brake related parts included new rear axle lines, Russel braided rear hose, Russel Speed Bleeders and new Raybestos drums.

After install I have bled and adjusted the rear drums several times.

The problem is I have a hard pedal, but it is very low. It feels as though there is insufficient travel now to fully engage the brakes. The cars stops, but fully depressed it bottoms out and the car slows to a halt, you cannot lock up the brakes.

Now before I started I always had a hard pedal. (Big cam, low vacuum) But I was always able to lock up the brakes at will with enough pressure, and the pedal did not bottom out.

Also, with the car off or on I can hold the pedal down without it slowly dropping. It's just that it now feels like I have insufficient travel.

In thinking it through and considering what I've changed, I suspect the new higher volume wheel cyclinders may be the problem. Could I be on the right track? Any suggestions to diagnose and fix?

Thanks in advance,
Rich

now that you've got the brakes good and bled, bleed them again.
then go do a few hard stops in reverse.

If you put larger volume wheel cylinders in then I'd expect your pedal to go lower because it will require more stroke of the master cylinder piston to fill that extra volume... You may have to now get a larger displacement master.

Also make sure that the shoes are adjusted fairly tight to start with, the less the shoes have to move out to meet the drum the less the master piston has to push the wheel cylinder pins out which equals the pedal stopping the car before the pedal reaches the floor or to a point that's lower than you like.

I used to have to re-adjust drums after a brake job there at the dealership, now I just make sure that the drum can hardly be turned by hand and everything works great. Just think "get rid of the slack" and it'll be better, but you may still have a volume issue.

Hmmm. In theory, it sounds like they're offsetting the problems of ceramic shoes (poor cold performance) and stiffer springs (more pressure required), with a higher performing wheel cylinder. But who knows if they've got it right? Seems like a good possibility for a parts mismatch here, especially if you know you've got poor vacuum to begin with.

But since you've already got all the parts in place, the first thing I'd do would be to try readjust the drums, particularly if you don't have a bunch of experince with drums. It's one of the most basic things, but takes practice to get right. And you can certainly go from a low and hard pedal to a high and good pedal with a more precise adjustment.

I'm kind of picky and just shooting for close dosen't cut it. My usual M.O. is to keep jacking up the side I'm adjusting, and spinning the wheel as I crank the adjuster till I hear that scraping sound. In my experinece, a properly adjusted drum will have more scraping sound than you would expect. If you don't hear anything, it's not tight enough.

Then, I drop the car, reach my foot in and hit the brakes a couple of times to seat the shoes, and give it the whole car a big shove in neutral to make sure I haven't gone too far. It needs to still roll freely. My street is quiet enough that I can do this, and you can definitely see the difference when you've gone too far and overtightened. The car should just keep rolling and coast to a stop. Go a couple of clicks too far and you will see the difference for sure.

In fact, it's really worth the lesson to purposely do that, just to get comfortable with what you're doing. And the ordeal of having to go back and loosen up the adjusters is good practice too. If nothing else, it makes you mentally visualize how the drum adjuster works, just so you can get the feel for what's going on inside there.

Of course, being picky I also drive it around the block and check it all again, since the parts need to seat. Plus, you need to remember that the heat of operation will expand things and close the tolerances, so there's got to be a little bit of clearance in there.

But give my techinque a try -- play with the tight/too tight threshold, and see how the car rolls from a shove. Works great for me.

Thanks folks for your suggestions. I've tried the bleed and adjustment several times. I'm pretty confident they are properly bled as I don't have a spongy pedal - it's hard. For the drum adjustment I put the car up on stands and adjusted one side until I heard and felt "some" drag, then did the other side until I had some more drag. It's a little difficult to determine if both sides have equal drag since it's a posi rear. It is possible I didn't tighten them enough, I'm going to go for a little extra tight tonight and see if that helps.

I'm leaning towards the parts mismatch simply because if it were simply the rear drum adjustments wouldn't the front brakes still give me good stopping power? (I forgot to mention it was the OEM power disc / drum setup.)

If I'm thinking this through right the larger rear cylinders need more fluid at a faster rate then before and the master cyslinder may not be keeping up. I was planning to get rid of the power booster and go with a manual set-up anyway but I really don't know about master cylinder choices. Would I just need a new master cylinder? Small bore sizes?

This stinks, I've busted my butt to get my Blue Dragon back on the road and now I'm afraid to drive it. I'm determined to fix this but don't want to just through parts at it. Any other suggestions?

Just spoke with the guy at Praise Dyno who was very willing to spend time with me on the phone BTW... he suggested more adjusting, to the over adjusting point, and running the car with the rear up on jackstands. He tells me sometimes bonded shoes are not perfectly symmetrical and don't fully seat in the drums. I may be adjusting just to high spots and I need to wear these down, adjust some more, and do this a few times to fully bed in. Another possibility is air made it's way into the front lines, but he's thinking hard pedal means air probably is not the issue. One other good tidbit of info is that I can use my original master cylinder without the booster, as long as the rod is shortened (some are adjustable, some have to be modified).

This all makes sense to me so I'll give it try tonight, greasy fingers crossed!

Arrrgh! No resolution last night...Dead starter!

Two new mini starters later ....

Back on the road! Basically I intentionally over adjusted the rear drums as advised, enough so that couldn't turn them by hand and I could feel the brakes drag when first leaving from a stop. The pedal height was improved but I could feel it lose height after a few miles of use. So I readjusted by driving in reverse and hitting the brakes. Did this a few times and now they seem to work consistantly, did 30 miles of windy, hilly back road with no mishap.

Next up the front brakes...