Brake problems, f*** EU regulation

[evilunclegrimace]

IIRC JB3, its a 1990 K1500 Z71 truck. Rear Abs fuction verified on ice... Not super impessive, but still ABS.. isch

I didn't relize that I was replying about 2 different trucks here. My reply was directed at the NorwegianViking.
There are 2 upgrades that will make your truck stop alot better. 1) upgrade your front brakes to JB5. This requires the Hubs, calipers,rotors,master cylinder and booster from a donor truck(or you can by new). 2) swap your rear diff for one out of a 4X4 suburban, that gets you 11" duo-servo rear brakes. The difference is well worth the time and expence.

 

[1990Z71Swede]

I figured you were confusing the Swede for the Norwegian...
JB3 Does not get much love it seems ... But on our truck they now work surprisingly well. The PO has done some brake work it seems. Front calipers are supposedly new... Maybe he f-ed up and put JB5's on, IDK. As long as they are working I'm not messing with them.

 

[El Tigre]

Adjusting rear drum will achieve a higher pedal. I have found additional benefit to installing a 10# residual pressure valve on the rear brake circuit. This prevents the return springs from pulling the shoes so far from the drum surface.

 

[Schurkey]

IIRC JB3, its a 1990 K1500 Z71 truck. Rear Abs function verified on ice... Not super impessive, but still ABS.. isch

JB3 was the weakest, crappiest power brake system installed on GMT400 trucks. I don't know if 1990 had the iron-body RWAL, or the aluminum body RWAL. The iron-body RWAL has it's own bleeder screw.

Adjusting rear drum will achieve a higher pedal.

Generally true. The craptastic 254mm Leading/Trailing shoe drums are infamous for being out-of-adjustment. This is generally due to needing the park brake to keep the service brakes in adjustment. So if you don't use the park brake frequently, the rear brakes suffer.

I have found additional benefit to installing a 10# residual pressure valve on the rear brake circuit. This prevents the return springs from pulling the shoes so far from the drum surface.

The leading/trailing rear brake shoes MUST to come to rest on the adjuster mechanism, in the same way that Duo-Servo shoes MUST come to rest on the anchor pin. If the springs are so weak that they can't overcome the pressure in the hydraulic system, the system is doomed to adjustment problems, dragging, and various other issues...which is why GM doesn't install a RPV in the system to begin with.

 

[El Tigre]

Sure works like a charm on mine. It works so well that I installed a 2# version on my disc brake-equipped Impala with similar results.

 

[1990Z71Swede]

I figured you were confusing the Swede for the Norwegian...
JB3 Does not get much love it seems ... But on our truck they now work surprisingly well. The PO has done some brake work it seems. Front calipers are supposedly new... Maybe he f-ed up and put JB5's on, IDK. As long as they are working I'm not messing with them.

This is whats on there, painted RED by the PO, not me, looks tacky me thinks.
RPO code says JB3, so that is what they should be, but are they?

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[evilunclegrimace]

Measure the rotor thickness and let us know what you come up with, also how about a picture of the brake booster.

 

[1990Z71Swede]

Measure the rotor thickness and let us know what you come up with, also how about a picture of the brake booster.

Those are JB3 fer sure, It´s just the calipers that I´m curious about.

 

[1998_K1500_Sub]

Those are JB3 fer sure, It´s just the calipers that I´m curious about.

Piston diameter on the low end calipers is ~63mm / 2.5”, give yours a check.

The JB5/JB6 brakes use a 76mm / 3” piston.

Heavier duty systems used 80mm or 86mm piston calipers.

Different boosters and MCs were used too, but I won’t discuss. Others may.

 

[1990Z71Swede]

Piston diameter on the low end calipers is ~63mm / 2.5”, give yours a check.

Alright, will do, thanks.