14b drum brake problems, GMT400

[D60]

I recently put new Centric riveted shoes and new hardware on a semi-float 14b in a '98 K2500. This is slide-on drums. Left side shown here:

When adjusting the brakes with lugnuts tightened down, the shoes seem to grab well before you can get proper adjustment. I noticed I can actually remove the drum and just knock the shoes around, or pump the pedal a couple times and the shoes seem to "re-center", allowing a couple more revolutions by hand before they grab rather suddenly. Sometimes it will only lock going forward but allow me to rotate in reverse, sometimes it won't allow any rotation at all. Again, some method of "re-centering" the shoes allows a couple revolutions before it grabs again. Not a GovLok issue, this is the brakes.

I only test drove a few miles with the new shoes and old drums. I figured the new shoes were somehow catching a lip in the old drums, so I installed two new drums, but results are EXACTLY the same.

This occurs on BOTH sides and the new shoes appear to be exactly the same width as the ones that were removed (2.5" on the SF 14b)

I find no grooves in the backing plate. The parking brake cables move freely. Adjusters are on correct sides.

This has ultimately translated to overheating brakes while driving.

Interestingly, this problem is not entirely without precedent. In a thread here Strouty describes very similar symptoms. He never really figured it out and ultimately swapped the primary and secondary shoes to the wrong locations. I actually asked him how this was working out and he said they work but he has to adjust them constantly.

I'm certainly not going to mount the shoes in the wrong positions, but I found it interesting this has been documented before. Thread here for those who care:
https://www.gmt400.com/threads/14-bolt-ff-brake-adjustment-and-setup-questions.59588/

I have also found other threads of 14b shoes grabbing before the lower adjuster could be opened enough.

At this point I'm stumped and particularly curious what @clinebarger has to say -- pretty sure he sleeps on a bed of old 14b drums

 

[Hirev]

Did you check brake shoe radius to drum? Some aftermarket brake shoes are horrible for matching the radius to the drum and allow to much odd movement.

 

[Lubener]

Did you check brake shoe radius to drum? Some aftermarket brake shoes are horrible for matching the radius to the drum and allow to much odd movement.

Unfortunately no place I know of still arc grinds the shoes anymore like the old days.

I was wondering if the shoe contact points on the backing plate are grooved and not having a smooth area. If everything is good, the entire assembly should be easily rocked back and for while "palming" the assembly at the nine and three oclock positions.

 

[doitmyself]

I know with my Patriot some aftermarket brand shoe pad (friction) material does not match the OEM Akebono's regarding length and mounting position. Investigate if your Centrics are the same as OEM.

Found a similar thread for FYI: https://www.pirate4x4.com/threads/gm-corporate-14-bolt-drum-brake-issue.2713087/

 

[Rob_Roy]

Watching - my Suburban is due to rear brakes.

 

[D60]

I know with my Patriot some aftermarket brand shoe pad (friction) material does not match the OEM Akebono's regarding length and mounting position. Investigate if your Centrics are the same as OEM.

Found a similar thread for FYI: https://www.pirate4x4.com/threads/gm-corporate-14-bolt-drum-brake-issue.2713087/

Thank you, that was one of the "other" threads I mentioned. It basically concludes with "normal" and just adjust-it-and-run-it. Unfortunately I can't just send it out the door when it's smoking brakes.

There's also the suggestion of shimming the drum due to center hole dia, but this condition is present with both the old drums (which I strongly suspect are OE from 1998) and new drums.

 

[D60]

Did you check brake shoe radius to drum? Some aftermarket brake shoes are horrible for matching the radius to the drum and allow to much odd movement.

I do have the old shoes still fortunately and this is something I plan to do. This is one thing that occurred to me, however all I might be able to do is eyeball radius of the shoe backer. Obviously I can't compare old friction material (likely from 1998) with new due to wear.

However even if radius is correct, if the holes/anchor pin placements are off it would move the entire shoe set within the drum.

I WILL SAY THIS: I did have to enlarge the hole for the parking brake arm pivot (with the e-clip retainer) about 1/16". I just attributed this to paint or variations in 14b specs because these axles had a LONG run and '98 was nearing the end. But perhaps it's indicative of poor QC

I do have some riveted Raybestos shoes coming. Hopefully Raybestos and Centric come from different facilities? @slacktide_bitog

 

[D60]

Also FWIW I've done this job before on my non-profit's 1989 K2500 (it's easy to get lexdysic with 1989 and 1998 which is the subject of this thread) and had NO problems. Same SF with slide-on drums.

I don't remember which shoes I used then but in that case one side was locking up because it was soaked with brake fluid from a leaking wheel cylinder.

So we know from results I was at least once capable of completing this job successfully.

 

[clinebarger]

May have to run them a little loose 'till they wear themselves to the radius of the drum, Then back up & tap the brake to self adjust them.

Or swap in some different shoes & hope they fit better.

 

[D60]

May have to run them a little loose 'till they wear themselves to the radius of the drum, Then back up & tap the brake to self adjust them.

Or swap in some different shoes & hope they fit better.

Yeah (more) new shoes are the next step I guess.

Have you ever seen wheel seals damaged from heat? These were brand new but I know the brakes got REALLY hot and I'm wondering if I should replace again? At least I did a LubeLocker gasket in case I need to yank the c-clips again....

Also thank you to everyone who's replied thus far. I'm determined to figure this out just to learn something if nothing else. It's the strangest thing.....

 

[clinebarger]

I doubt the seals got hurt, The drum is the heat sink & a pretty large one.

The secondary shoe wedges itself against the drum when applying the brakes going forward (Duo Servo), Take a look at the contact pattern on the shoe.....If its small & in the middle somewhere......The radius of the shoe is to small.
If the wear pattern is on the tips of the shoe....The radius is to large.

 

[lbhsbz]

Try a different brand of shoes, and make sure they look different (different color, etc..). There are 3 or so factories that produce most of the shoes you see in the aftermarket....you want some from a different factory. Find some with a brown colored web/steel and try those, they'll be arc'd a bit different

 

[D60]

Try a different brand of shoes, and make sure they look different (different color, etc..). There are 3 or so factories that produce most of the shoes you see in the aftermarket....you want some from a different factory. Find some with a brown colored web/steel and try those, they'll be arc'd a bit different

Funny you say this....this is the conclusion I'm slowly reaching I think. I installed the new shoes yesterday -- they were Wagner not Raybestos as I previously said. The problematic shoes were Centric "heavy duty"

Now with the Centrics removed and the Wagners installed I can properly adjust the brakes, and they don't grab suddenly like a Chinese finger trap.

I traced the arc on cardboard of the Centric and compared the Wagners -- I do believe there is a slight variation but man it's subtle. I think the Centrics are effectively a larger radius, causing them to catch at either end of the friction material and "kick" the shoe(s) one direction or another.

I will say with the Centrics this was only evident once the lugnuts were TIGHT. If you backed off the lugs so the drum could relax even the tiniest bit, the Chinese finger trap effect vanished. This really stumped me as I've never seen this behavior before. This was with used drums or new drums.

It would seem the GOOD NEWS is that it wasn't really my fault and a result of crappy parts. Frustrating but I'd feel worse if it was my stupidity -- and I have no shortage of stupidity.

Shown here is a Centric on bottom driven about 200 mi vs a new Wagner on top. The Wagner employs more rivets so it's almost surely a different manufacturer.

Ironically the rivet pattern of the Centrics is OEM -- not that rivet pattern affects arc/radius

I also did not have to drill the parking brake arm pivot hole on the Wagners.

Test drive today.

 

[Nukeman7]

I WILL SAY THIS: I did have to enlarge the hole for the parking brake arm pivot (with the e-clip retainer) about 1/16". I just attributed this to paint or variations in 14b specs because these axles had a LONG run and '98 was nearing the end. But perhaps it's indicative of poor QC

I also did not have to drill the parking brake arm pivot hole on the Wagners.

Test drive today.

I believe this tells the story about the (lack of) quality control of the Centric brake shoes. While I have not experienced poor quality with the Centric rotors and Posi-Quiet brake pads in the past, I suspect most of their products are being manufactured overseas like their rotors (China).

 

[D60]

I believe this tells the story about the (lack of) quality control of the Centric brake shoes. While I have not experienced poor quality with the Centric rotors and Posi-Quiet brake pads in the past, I suspect most of their products are being manufactured overseas like their rotors (China).

Yeah I'm kinda bummed. I never considered Centric top shelf but thought they were decent -- maybe middle of the road. But maybe not

 

[nthach]

Aye, I have to deal with drums on a K1500 Blazer soon. Having a friend order parts from the jungle store, Raybestos drums and Powerstop molded shoes. Will I be asking for trouble? I have a hunch all the shoes are made in China or India unless it’s GM OE and even so. Only DFC claims they machine drums on dedicated equipment and their shows are “precision arc ground”. I know for Japanese things, aftermarket drum brakes are a sore point of contention.

 

[97prizm]

I recently put new Centric riveted shoes and new hardware on a semi-float 14b in a '98 K2500. This is slide-on drums. Left side shown here:View attachment 282054

When adjusting the brakes with lugnuts tightened down, the shoes seem to grab well before you can get proper adjustment. I noticed I can actually remove the drum and just knock the shoes around, or pump the pedal a couple times and the shoes seem to "re-center", allowing a couple more revolutions by hand before they grab rather suddenly. Sometimes it will only lock going forward but allow me to rotate in reverse, sometimes it won't allow any rotation at all. Again, some method of "re-centering" the shoes allows a couple revolutions before it grabs again. Not a GovLok issue, this is the brakes.

I only test drove a few miles with the new shoes and old drums. I figured the new shoes were somehow catching a lip in the old drums, so I installed two new drums, but results are EXACTLY the same.

This occurs on BOTH sides and the new shoes appear to be exactly the same width as the ones that were removed (2.5" on the SF 14b)

I find no grooves in the backing plate. The parking brake cables move freely. Adjusters are on correct sides.

This has ultimately translated to overheating brakes while driving.

Interestingly, this problem is not entirely without precedent. In a thread here Strouty describes very similar symptoms. He never really figured it out and ultimately swapped the primary and secondary shoes to the wrong locations. I actually asked him how this was working out and he said they work but he has to adjust them constantly.

I'm certainly not going to mount the shoes in the wrong positions, but I found it interesting this has been documented before. Thread here for those who care:
https://www.gmt400.com/threads/14-bolt-ff-brake-adjustment-and-setup-questions.59588/

I have also found other threads of 14b shoes grabbing before the lower adjuster could be opened enough.

At this point I'm stumped and particularly curious what @clinebarger has to say -- pretty sure he sleeps on a bed of old 14b drums

Have you had any issues with the parking brake? My cables stretched on my neon and didn't retract.

 

[D60]

Aye, I have to deal with drums on a K1500 Blazer soon. Having a friend order parts from the jungle store, Raybestos drums and Powerstop molded shoes. Will I be asking for trouble? I have a hunch all the shoes are made in China or India unless it’s GM OE and even so. Only DFC claims they machine drums on dedicated equipment and their shows are “precision arc ground”. I know for Japanese things, aftermarket drum brakes are a sore point of contention.

I really don't know what the answer is. The Brakebest drums from O'Reilly sucked. They introduced an immediate pulse that was not there before.

Also check out the sweet weight MIG welded on -- because that works out so well w cast iron

The much smaller weight on the other side came off (see comments above about wire feed + cast iron)

In contrast the OEM drums appear to remove material to balance -- FAR more elegant

I'm VERY reluctant to let O'Reilly turn these OEM drums -- can their brake lathes do a 13" drum without gobs of chatter?? I don't know

 

[nthach]

Aye. This is why I went OEM Toyota for the van. They weren’t much more than the aftermarket options. I have a feeling BPI/First Brands makes the GM aftermarket line, as well as Napa’s.

 

[D60]

Ok well I think I can close the chapter on this repair but man it was an epic saga.

98% of the problems were from crappy parts:
1) Centric shoes grabbed inexplicably
2) Brakebest drum out of round and caused pulsing when braking
3) the new O'Reilly master cylinder seemed to cause very poor pedal feel

What I did to address this:
1) replaced shoes with Wagner and adjusted to light drag
2) replaced one drum back to the original. The other drum seems ok
3) I tried bleeding and reverse bleeding the O'Reilly mc once new shoes were on and adjusted, but it just never was right. I had ordered a new AC Delco (but still made in China!) and installed that.

The AC Delco mc was an immediate improvement BUT even this punked me because the rear output was leaking under pressure until I snugged the fitting to the stupid level. I kept wondering why the brakes were good and would then just fade severely ‐- well, squirting fluid from a fitting will do this.

All told I can't even tell you how many times I bled with the help of my wife, pressure bled with my Branick, activated the ABS bleed with my Otofix and reverse bled with my Phoenix.

The morals are:
1) buy the best parts you can
2) just say no to GMT400 brakes

Also FWIW I didn't find reverse bleeding to really be better or worse than pressure bleeding this system (JB7, vac booster)