I'm at a loss..

[PrairieDrifter]

Wild guess - something like this that is keeping the shoes slightly engaged?

63 drum brake backing plate - grooves in contact pts - CorvetteForum - Chevrolet Corvette Forum Discussion

C1 & C2 Corvettes - 63 drum brake backing plate - grooves in contact pts - I have grooves in the contact pads of my drum brake backing plates. How deep is too much? They are about 1/32 to 3/64 deep, can I just smooth them out? seems that getting the backing plate off the rear axle to fix it...

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Nope! Perfectly flat and well lubed. They're in great condition. I love the outside the box thinking though!

I couldnt tell you if they are bent though. If both are bent I've got bigger problems I would say lol.

 

[mxer147]

Week return springs?, the spring rate significantly decreases as the temperature increases. Just a guess from a backyard mechanic.

 

[PrairieDrifter]

Week return springs?, the spring rate significantly decreases as the temperature increases. Just a guess from a backyard mechanic.

I've tried two sets of hardware as well. Same results. They seemed to have fought me getting it together as normal as any other of the 100's of drum brakes I've done.

 

[rusted nuts]

Also it would take a real like 30 mile drive to get em hot hot, but now it's less than 10

May be they are self adj too tight

 

[PrairieDrifter]

May be they are self adj too tight

I made my own adjusting slots on the backing plates so I didn't have to pull the wheels and drums off. I can get in there and get some slight free play of the shoes, which is even more confusing.

If it was self adjusting too tight, I literally can't do anything about that? Correct? Maybe new adjusters, but that seems redundant, the locking arm for the adjusters are plenty tight on the star wheels. The adjusters are new too.

It almost seems like the shoes and drums aren't made for each other, or aren't interfacing correctly. Even though they're both the big brakes.

 

[PrairieDrifter]

May be they are self adj too tight

But also like i said, if I adjust them any father off, I lose brake pedal feel, aka braking power/contact.

 

[rusted nuts]

Brake hoses from ORD and they aren't very old? Yeah, I highly highly doubt they are a restriction.

I've seen brake boosters cause a brake drag before. The more you drove it, the worse it got. The booster was evidently keeping light pressure against the master cylinder.

Had a brake booster do the same think on a Dodge It had a small clip inside that came lose and held the rod from returning

 

[rusted nuts]

I made my own adjusting slots on the backing plates so I didn't have to pull the wheels and drums off. I can get in there and get some slight free play of the shoes, which is even more confusing.

If it was self adjusting too tight, I literally can't do anything about that? Correct? Maybe new adjusters, but that seems redundant, the locking arm for the adjusters are plenty tight on the star wheels. The adjusters are new too.

It almost seems like the shoes and drums aren't made for each other, or aren't interfacing correctly. Even though they're both the big brakes.

I never used the self adj,, I just stretch a spring across the star wheel and adj by hand the old school way. You could try that way and that would tell you if the self adj were causeing it.

 

[PrairieDrifter]

I never used the self adj,, I just stretch a spring across the star wheel and adj by hand the old school way. You could try that way and that would tell you if the self adj were causeing it.

That's a good trick. But I really don't believe it's the adjusters. I adjusted them off in the garage then 2 light brake pedal applications and I was on the highway for 10ish miles and they were hot already, with the pedal feeling sloppy because they were adjusted to far off. No way they adjusted there. Even so id rather not have to adjust my brakes manually. Dont need to add another thing to the regular check list of an old vehicle.

Also a side note. When I did the master it easily slid flat into position on the booster with no resistance whatsoever.

 

[PrairieDrifter]

I also have put a little over 1000 miles on the most recent brake job in hopes that it would wear in. As well as I daily drive this truck. The booster seems to be the only component left, but I really don't believe that's the issue.

I can't remember how many miles on the last brake job, ill have to look at my records.

 

[rusted nuts]

That's a good trick. But I really don't believe it's the adjusters. I adjusted them off in the garage then 2 light brake pedal applications and I was on the highway for 10ish miles and they were hot already, with the pedal feeling sloppy because they were adjusted to far off. No way they adjusted there. Even so id rather not have to adjust my brakes manually. Dont need to add another thing to the regular check list of an old vehicle.

Also a side note. When I did the master it easily slid flat into position on the booster with no resistance whatsoever.

My bad booster only screw up part of the time. I thought it was a bad hose or clap. at 1st

 

[rusted nuts]

I also have put a little over 1000 miles on the most recent brake job in hopes that it would wear in. As well as I daily drive this truck. The booster seems to be the only component left, but I really don't believe that's the issue.

I can't remember how many miles on the last brake job, ill have to look at my records.

That's a good trick. But I really don't believe it's the adjusters. I adjusted them off in the garage then 2 light brake pedal applications and I was on the highway for 10ish miles and they were hot already, with the pedal feeling sloppy because they were adjusted to far off. No way they adjusted there. Even so id rather not have to adjust my brakes manually. Dont need to add another thing to the regular check list of an old vehicle.

Also a side note. When I did the master it easily slid flat into position on the booster with no resistance whatsoever.

Well be sure to let us know what You find, Could also be a bad MC even if it is new. I would be pumping that brake pedal like crazy then cracking some lines and hoses to see if there was still press in the lines

 

[rusted nuts]

I am almost positive it is, I have a nice floppy pedal at rest, a couple hairs of free play. It's definitely not the master, it acted the exact same. I've changed nothing else but shoes and pads recently, everything else is 1 year to 3 years old.

I think the new parts are the problem like drum or shoes, but Ive tried multiple and don't know what to do.

The proportioning valve cuts off flow to one section of brakes when it feels a loss of pressure. I haven't had a loss of pressure at the front since I've had the problem, we'll ever for that matter, as well as I have great working brakes. Maybe it could be slightly off, but no brake light and I never had a leak on the fronts.

A couple of hair of free play?? You should have 1/4 inch at lease Maybe 1/2 inch

 

[PrairieDrifter]

A couple of hair of free play?? You should have 1/4 inch at lease Maybe 1/2 inch

I'd say 1/8 to 1/4. From my experience is plenty.

 

[SirRobyn0]

I've also seen where the rod under the dash was adjusted out to far, and caused drag issues similar to yours but that usually only happens after someone has messed with it.

It would be helpful if you had a IR heat gun and could take temps of each wheel when the symptoms are occurring, I'm just throwing that idea out there if you do have one.

No matter what the cause of the drag is once the shoes or pads if it were the fronts (not saying it is being hypothetical) heat up the rotors or drums the metal expands and the drag increase exponentially. Also if something is acting like a check valve (a bad hose) as others have indicated. Generally a bad hardline will leak, but if a hardline is crimped or bent it can sometimes cause a restriction.

Is it just one drum or both dragging. Also it would be good if you could tell if the fronts are dragging even if only slightly. Lets face it if it's all 4 involved, that could really narrow down your search.

Even if you think the play is enough in the pedal you could try adding a bit more as something free to try.