front brake grabbing (locking)

[wlf89]

got a 67 chevy c10 which has 4 wheel drum brakes. other day when pulling out of drive the brakes sounded like they where holding, figured out it was the front left brake making the noise. jacked the truck up, and it will spin for as long as i go backwards, but will only spin two or three rounds before it locks up if i spin it forward. took wheel and drum off and everything looks good, drum, shoes, hardware everything looks good. dont see no leaks nowhere and the fluid is still full in the master. went ahead and bleed the left side while i was there looking at it but didnt make no difference. have replaced master cylinder, wheel cylinders,brake shoes,and drums, and new hardware kit in the last 4 months.

[HO455]

Is it possible that the left side hardware is on the right side. I recovered a car that was stolen and the thieves had swapped the brake parts around and caused a similar issue. The other things that pops to mind is how old are the hoses?

[Wrenchbender Ret]

Grind a bevel on the edge of the linings. Sometimes the edge digs in to the shoe & causes this. It could be the hose swollen up inside like HO suggested.
They don't give much attention to drum brakes any more. They used to cam grind the linings & bevel the edges & rivet them on. Now they are bonded on & that's it.
George

[wlf89]

ground a bevel on the shoes with no difference. its just in a certain spot that it locks up, maybe the shoes or drum is that much out of round? it gets tight when spinning backwards in one spot but doesnt lock up.

[demian5]

Is the hub loose? Do the bearings need to be adjusted?

Are the back brakes 100%? No leaking fluid?

[jamyers]

We had a similar situation, the passenger front drum brake would "self-adjust" itself too tight, to where it was pulling the steering wheel to the right when you applied the brakes, and was always barely dragging so that the drum was always warm when the others would be cold.

You could turn it either direction, but backwards was easier (because drum brakes self-engage with going forward and they contact the drums) - and it only drug at 2 points in a revolution.

The culprit was an out-or-round drum, that let the self-adjusting mechanism go too tight whenever the drum was at the "wide" part, then that wheel would drag.

I don't know about parts places around you, but here O'Reilly Auto parts can turn drums for something like $10, assuming you'll have enough meat left on them to stay in spec.

Otherwise, new drums are $25 each at Summit.

[tdangle]

Another easy thing to overlook is that the short (primary) shoe lining goes toward the front of the vehicle.

[jamyers]

I re-read your OP, if you've got new drums they *should* be nice and round, unless you've gotten them really hot and then kept holding the brake pedal (like you'd do driving in Dallas - going 75 one minute then braking hard and sitting still for 5 minutes)

If something is only touching at certain points as the drum rotates, then either the hub/drum is moving, or the drum isn't round.

Make sure the bearings are adjusted properly (just a *tiny* bit of slack), then if you have a dial indicator you can mount the drums facing outwards and check the inside surface for out-of-round.

[wlf89]

checked the "new" brake drum with less than 50miles on it and it was out of round. took it to the auto parts store to have it turned. he said it was good bit out of round. put it back on last night and its all good now. just goes to show the word new dont mean nothing these days.

[jamyers]

Originally Posted by wlf89

checked the "new" brake drum with less than 50miles on it and it was out of round. took it to the auto parts store to have it turned. he said it was good bit out of round. put it back on last night and its all good now. just goes to show the word new dont mean nothing these days.

I hear ya! At least you got it straightened out, though

[Steeveedee]

In my experience a new front drum should be mounted to the hub and checked for out of round before it leaves the parts store. Just a little bit of tolerance buildup can cause an "out of round" condition. I'd recommend that you mark the drum and hub so that whenever you remove the drum from the hub, that it goes back on in the same orientation.

[Boog]

The first couple of times I was told I better have new drums turned before install I thought thats just crazy. New parts dont need turned. Two mechanics told me I’d be pulling them off right away. They were right. It is nuts. New parts made to spec should not need finishing before install. Period. It was explained to me after manufacturing they are just dumped in a metal bin and cooled that way so they aren’t stacked neatly and tend to warp some. Sounds bout right.

[Steeveedee]

Originally Posted by Boog

The first couple of times I was told I better have new drums turned before install I thought thats just crazy. New parts dont need turned. Two mechanics told me I’d be pulling them off right away. They were right. It is nuts. New parts made to spec should not need finishing before install. Period. It was explained to me after manufacturing they are just dumped in a metal bin and cooled that way so they aren’t stacked neatly and tend to warp some. Sounds bout right.

At the brake drum plant, sometimes too, I guess.