M1028 left right brake balance

[Swfb]

During the anual check my m1028 did not pass the brake test.

The difference in brake force, between the left and right rear wheel, is about 50%.

2 years ago I did not had this problem.
And no parts had been replaced between both checks.

I can't seem to find what is causing this problem so I hope one of you can help me.

What I have done so far:
- Adjusted the brakes as mentioned in the TM.
- Switched drums from sides
- replaced brake pads
- replaced brake cilinders
- replaced springs
- cleaned all internal brake parts
- replaced parking brake cable
- replaced brake hose
- new brake lines from under the cab till both wheels
- old brake balance (load regulated) removed
- put in a new adjuster
- replaced proportioning valve
- new steering gear
- other power steering pump

Between installing and replacing the parts I have had the brakes tested multiple times.
It does not make any difference, it is still around the 50%.
And it's always the driver side that is failing.

What could cause this brake failure?
Brake booster?
Master cilinder?

 

[frank8003]

somebody squashed a rubber brake line so fluid would not leak out when fixin brakes?
Disconnect lines to rear rakes and blow them out?

 

[Swfb]

somebody squashed a rubber brake line so fluid would not leak out when fixin brakes?
Disconnect lines to rear rakes and blow them out?

I have replaced all the lines with ptfe lines.
And I have got 1 rear wheel thats good and the other one keeps having problems. So I believe the line is open. Because of that 1 wheel is working

 

[Keith_J]

Sounds like an assembly issue. These drum brakes are the typical servo type, using the brake drag to also energize the clamping force.
The best way to check is to jack up the rear axle and remove both drums to compare the assembly, they should be mirror images of each other.
The 50% right side bias is very indicative of this condition.

 

[Swfb]

Yesterday I have tested the brakepressure on both sides of the axle. And both sides had the same pressure on the bleedingscrew. 490psi.

I have added a couple of pictures to this post.
- The starting point with the brake parts installed and tested 2years ago and not having any problems. And while they have not been changed the problems started.

- The next with the new cylinder mounted.

- And the last few with al new parts.
With the new shoes mounted I did saw they are having marks of the drum in the side.
I used an angle grinder to "break" the edges.

The width of the old and the new are the same. And I can't understand why the brakes worked without a problem and now they don't want to work again as they are supposed to.

Does anyone see a error in the parts mounted as on the pictures?

 

[cucvrus]

Is it just me or do you have both front brake shoes on the right side? I see the front brake shoes are mounted on the right axle. The short shoes with the lesser brake lining always goes toward the front of the truck. Check it out. I may be seeing things but it appears the shoes lining are the same in the picture and the lining should be longer on the rear shoe.

See how the front shoe has shorter lining at top? That is the correct installation. Each new drum brake set has 2 long shoes and 2 short shoes. I hope you understand. Maybe I am incorrect and see something different but I seen it many times. Good Luck. Report Back. Thank you.

 

[Swfb]

Is it just me or do you have both front brake shoes on the right side? I see the front brake shoes are mounted on the right axle. The short shoes with the lesser brake lining always goes toward the front of the truck. Check it out. I may be seeing things but it appears the shoes lining are the same in the picture and the lining should be longer on the rear shoe.

See how the front shoe has shorter lining at top? That is the correct installation. Each new drum brake set has 2 long shoes and 2 short shoes. I hope you understand. Maybe I am incorrect and see something different but I seen it many times. Good Luck. Report Back. Thank you.

Thank you Rick, I have just measured a spare set to fully understand your post.

Enclosed some photos as a refference. (In mm)

I'll open the truck later this week to check it.

 

[cucvrus]

Yes. The shorter shoes goes toward the front of the truck. You have a correct set pictured. Metric measurements work for me also. Check it out and make sure you have it correct. I am just putting that out there as an option or cause of the issue you are experiencing. We do a safety inspection here in Pennsylvania. And Pennsylvania has a very thorough safety inspection. I had a license to do state inspections until a year ago. Mine expired and I never renewed them. I have not officially inspected a vehicle in 35 years. I have replaced many brake pads and shoes in my lifetime. Good Luck. If it helps I am happy. If not I tried. Be Safe.

 

[nyoffroad]

Yes. The shorter shoes goes toward the front of the truck. You have a correct set pictured. Metric measurements work for me also. Check it out and make sure you have it correct. I am just putting that out there as an option or cause of the issue you are experiencing. We do a safety inspection here in Pennsylvania. And Pennsylvania has a very thorough safety inspection. I had a license to do state inspections until a year ago. Mine expired and I never renewed them. I have not officially inspected a vehicle in 35 years. I have replaced many brake pads and shoes in my lifetime. Good Luck. If it helps I am happy. If not I tried. Be Safe.

Good catch, I was thinking along the same lines. After all the pressure is the same then the stopping force should be the same IF all parts are equal. I thought he had installed the primary shoe in the rear position not both primaries on one side!

 

[cucvrus]

It may be a mis-guided guess. But I wanted to put that out there.

 

[royalflush55]

Are you sure both wheel brake cylinders are the same bore?

 

[Swfb]

I have just taken the drums of the Chevy.

- brake shoes are correctly mounted. The shoes with the least ammount of brake surface facing forwards.
- both wheel brake cylinders are the same.
Both sides new.

What I do see, and I have forgotten why, is that I only have replaced one side of the shoes. Its been stored for 2 years now. I have to go look for the other 2 halfs.

Another thing I see is the wear pattern on the shoes. The old shoes are in contact with the drum on almost the full surface.

The new on a less. As shown on the pictures. It almost looks like they have to break in.

I have used the TM to adjust the brakes.

 

[cucvrus]

Bell shaped drums was my next guess but I thought you would have guessed that. That is often a common issue and is greatly overlooked. On the newer vehicles the rotors have areas that are solid rust and the brake lining does not make contact in the rusty areas. Maintenance. I don't know anywhere to get drums and rotors turned down anymore. Now I just replace the drums and rotors and recycle the used parts. Sad thing is and I ask this all the time. Are the Chinese replacement drums and rotors as good as the originals. Then I think about it. The originals are made in China now also. And who cares. As long as the vehicle stops when you hit the brakes. That is the desired result. Good Luck.

 

[nyoffroad]

Are you sure both wheel brake cylinders are the same bore?

Now that would NEVER have occurred to me!

 

[Swfb]

I have corrected my mistake and also replaced the shoes on the passenger side.
Also readjusted both sides and the parkingbrake again as discribed in the TM.

I made a couple of stops and it all looked good. See the pictures below.

This morning I loaded it up and to the brake test again. And....... succes!
Brake pressure / force on both sides are now the same and past the test!

I'm happy with the results I only still don't understand it. For me it's not clear how replacing parts on the passenger side make the driver side better.

Just to be clear, always replace both sides together! While I thought I had done that it made me search for a problem on the wrong side of the axle.

 

[chevymike]

All I can say is I HATE DRUM BRAKES Nice job on fixing

 

[Rutjes]

All I can say is I HATE DRUM BRAKES Nice job on fixing

I think I almost talked him into ordering a disc brake conversion kit, but then he found the problem and fixed it. I was too late.

 

[Swfb]

I think I almost talked him into ordering a disc brake conversion kit, but then he found the problem and fixed it. I was too late.

Soooo close ! The next time I will!