Brake Mystery

[AMXguy]

 Got some weather to take my recently finished total restoration out today and I have a brake problem I can't figure out.

 The front left brake pulls bad, jerks the wheel in your hand.  if I had to make a hard stop it would be ugly, but on normal stops it pulls but is drivable.   it has to be fixed.

 I pulled the drum off and everything looks nice, original drums have been turned and new slaves installed.  the shoes looked good so I cleaned them up with sandpaper and brake cleaner.  I figured 30 year old ones were better than most new ones.  I can make all 4 wheels slide on pavement at low speed  if I hit the brakes hard.


 Any ideas?  I'm about to replace the shoes even though they look good I don't know where else to look .

[Beekeeper]

You mentioned brake pad but then talked about shoes so I'll assume you meant shoes and have four wheel drums.

Does it only pull when you apply brakes or is it constant pull? If you were to jack up the front end, each of the front wheels should spin a couple full rotations when spun hard by hand. If you jack it up and find the left front wheel doesn't spin nicely, then I'd suspect a sticking wheel cylinder. Another possibility is the shoes don't retract because of a broken spring, incorrect install, or the adjuster at the bottom is badly out of adjustment.

You mentioned new restoration....did everything work good last time you drove it or is this a maiden voyage with new brake system? If this is a new system, verify your plumbing at the brake proportioning valve below the master. Don't typically see issues here since the valve has different size inlets to prevent hooking lines up wrong but worth a look. The rear line gets less pressure than the two for the front so I suppose it's possible to get this wrong on a whole new system.

[AMXguy]

Yes it is 4 wheel drum.  it does the same thing in reverse it does going forward, except it pulls the other way of course.

Both wheels spin fine, I have them adjusted to drag just a tiny bit, I tried backing them off a little and saw no difference.   I jacked it up and turned both wheels by hand as my wife put pressure on the pedal,  hard to say by hand but both front wheels lock up to where I can't turn them at about the same pedal pressure.  but under load driving there's no comparison . all new hardware and everything seems to be in order .

This car was used for a drag car before I restored it so I assume the brakes worked okay but I'm not sure.  everything is stock I just did a normal brake job minus replacing the shoes which look good. 

I put new lines in ,  I'm not sure how I could have hooked them to the proportioning valve wrong but even if I had it doesn't seem like the rear brakes would work fine which they do. 

[brads70]

Would having the shoes on backwards on one side cause this?

[AMXguy]

I checked that,  long shoe is on the back on both sides.

[brads70]

I checked that,  long shoe is on the back on both sides.

[jimynick]

What about a wee bubble still in the rt frt line/cylinder? There are gauges to tell you the pressure applied at the wheel cylinder. A possible kink/bend/leak in a line? I'd bleed the beejesus out of the frt end again. We use a piece of 1/8" clear tubing that we squeeze over the bleeder screw and it's end is immersed in a bottle with brake fluid in the bottom to prevent sucking any air back while bleeding. Just my 

[Beekeeper]

Is it possible that the left side is actually working good and the right is barely working? That might also explain the pull to the left side. I'm just throwing out ideas here....original drums can only be turned so much before they are out of tolerance. If the right drum has been turned too much, couldn't the shoes have trouble expanding out far enough to get good pressure against the drum? Or if the right wheel cylinder was sticking, I suppose you could have a similar problem. I've never had an issue like yours but I'm thinking if the right front wheel was not braking very well, it might also feel like the left was biting too hard. Most brake parts are made in China these days so it really wouldn't surprise me to find a defective wheel cylinder.

As far as the proportioning valve, you probably got it right. I only mentioned it because there is one port which feeds both rear brakes at lower pressure and two other ports which separately feed the right and the left wheel at higher pressure. I was theorizing about the right line accidentally going into the port for the rear. This would give the right front wheel lower pressure than the left and the rear brakes would get a supply line at higher pressure which might not be that noticeable.

[Beekeeper]

What about a wee bubble still in the rt frt line/cylinder? There are gauges to tell you the pressure applied at the wheel cylinder. A possible kink/bend/leak in a line? I'd bleed the beejesus out of the frt end again. We use a piece of 1/8" clear tubing that we squeeze over the bleeder screw and it's end is immersed in a bottle with brake fluid in the bottom to prevent sucking any air back while bleeding. Just my 

I agree...definitely worth the effort. It would be nice if it was just a little left over air in the right wheel cylinder.

[AMXguy]

I can bleed them again,  but at 10 mph I can lock all 4 up so I know they're working pretty good.

You can be going 20 mph and make a  90 degree  left turn without touching the steering wheel.

I ordered a set of shoes,  the old ones look great but something is going on here that seems like a place to try. 

 

[mopar jack]

If you rebuilt the front suspension, I would check the strut rods and the tie rods

[jimynick]

The brakes will work if there's a bubble in the line- just not properly. In the millisecond that it takes the master to compress a bubble, the other, non-bubbled side has been applied and that could be why the car stops, just not evenly since it's taking that littlest bit to develop equivalent pressure in both sides. That's my story and I'm sticking with it. The only other logical cause would be a dragging wheel cylinder as mentioned. As for the drums being oversized, the brakes don't know or care about that since when you adjust the shoes, you remove any gap caused by cutting them and they only need to travel the clearance gap which should be the same if they're both adjusted the same. Again, just my 

[AMXguy]

I checked the strut rods they're tight.  I had my wife drive and hit the brakes and everything looks fine no movement fore or aft in the wheel well.

As soon as I get the new shoes on ( they sent the wrong ones )  I'll bleed them again for good measure. 

I did notice only about half of the shoe on the locking up side was making contact with the drum in an uneven pattern.    which you'd think would cause less braking,  but I don't know  we'll see what new ones do.

[jimynick]

Drum brakes can be a PITA and back in the day there was a machine that traced the exact curvature of your drum and translated that to a grinder which duplicated it on the shoes. The whole purpose of that was to ensure full and complete contact between the shoe and the drum, but they're like wheelwright tools and are exceedingly hard to find today. Keep trying, I'd love to hear what the eventual outcome is. 

[73440]

http://p15-d24.com/topic/35484-ammco-brake-shoe-grinder/

About halfway down the thread are pictures of an Ammco brake shoe grinder.