[HotRodMan]

I have a 1973 Javalin AMC 6 cylinder, with dual reservoir master cylinder, drum brakes front and rear, no power brakes.

I recently did a complete brake overhaul. I replaced all 4 wheel cylinders, installed a new, not rebuilt, master cylinder, all new brake shoes. I had scoring on one of the rear drums so I had both rear drums turned. The front drums looked good so I left them alone. The new master cylinder has the same 1 inch piston size as the old one I took out. Completely cleaned all brake hardware, cleaned the drums with lacquer thinner, adjusted brakes on all 4 wheels, bled the brakes, bench bled the master cylinder, have a firm hard peddle.

The problem is that it takes about 50% more effort with my foot to stop the car as is did with my old brakes. I have re-adjusted the brakes and re-bled the system (no air) after driving the car for a week. I have turned each wheel by itself and applied the brake while the car was up on jack stands and the brakes work fine. No binding or problems any where.

Does anyone have an idea of what the problem is?

[crazy larry]

start here it's a pdf.

[Wrencher]

It may take a short while for the shoes to seat, also, did you install the shorter lining shoe towards the front on each wheel?

[Sleeve396]

I also had a similiar experience with my 68 chevelle with a big block transplant and original non power drum brakes all around.
What I found was that my brake drums were very glazed and my new brake shoes were also glazed pretty much sliding in the drum without actually grabbing. I tried a new set of better quality shoes and this time turned all 4 drums with a slightly rougher finish and it made a considerable difference. It also seems to be better if you do break in drum brakes by not doing the usual 100 to 0 panic test with brand new shoes I did not see what difference it made at the time but the old timer that started me on my car addiction told me that cetain brakes need to cure in or seat in to their respective drums before they wilbe at their best.
ps make sure that you measure the drums many times they are oversized from years of brake jobs. good luck and let us know whats up.

[HotRodMan]

Thanks for the replies. Yes I did install the primary shoe to the front on each wheel. When I had the brakes disassembled, I tried to break up the glaze by sanding the drums and the shoes with 150 grit sandpaper before I installed them back on the car. I have owned this car since it was new in 1973. I have been doing the brake jobs on this car for 30 years and this is the first time this has ever happened. The front drums have never been turned, this was the first time the rear have ever been turned. You may have something with the brake shoes not grabbing the drums correctly, but I don't know what I could do about it except drive the car for a while. It feels like the brake shoes are just sliding over the drums when I apply the brakes. I noticed the brake shoe material had little specs of something in there that the old shoes did not have. I can stop the car without putting anyone in danger, it just takes more leg effort than it did before.

[johnsongrass1]

Lifetime warranty shoes are guaranteed that long for a reason. They are hard as hell and take a while to heat cycle.

[dmc12mk3]

Possibly the wrong size piston in your master cylinder?

[adtkart]

Have you pulled the drums and looked at the shoes for wear pattern. Many years ago, a shop that I worked at had a machine that was used to cut the shoes to match the drums. You would measure the drums, and cut the shoes to match. When the brake shoes are re-lined, they usually end up with a different radius than the drums. The shoes may only be partially touching the drums because of the different radius. This causes the shoes to have to "wear in" for those drums.

Look at the shoes and see if they appear to be wearing at the top and bottom, or only in the middle. If they are not contacting on the full lining, you will either need to, 1) hope that they wear in soon(not likely with the "life time warranty" type), 2) file them down to match the drums, 3) replace them.

Note that the shinny specs usually indicate "semi-metalic" pads or shoes. They are considerably harder than the others, so they last longer. My experience with this is that they also eat up rotors and drums quicker. Now, instead of replacing the linings, say every 20000 miles, you replace the linings and rotors/drums every 30000 miles. The semi-metalic are more expensive, plus the cost of the drum/rotor. Guaranteed sales for the manufacturer!

[ShamrockCustoms]

Definitely check for leaks. Is this power brakes or manual? If power, check the booster and vacuum line. Also, did you check the new master cylinder to see if the rod clearance is the same as the old one? if the distance from the end of master piston to the rod is different, it won't brake the same. It seems you have checked most everything else. Set the emergency brake yet to see if it works right? Adjusters may need additional care. If you have never had the prob on 30 years, then rest assured that its' most likely a physical problem with the new parts........one of them at least.


good luck!!