1998 K1500 JB6 C5S Heavy Half with mixed calipers

[REM777]

Dear friends, truck got stolen and the guy drove it like he stole it - got truck back - by the size of the hitch draw head was towing something heavy - anyway - had to do calipers because brakes were down to squeelers . During pad replacement I noticed the two calipers are of different "styles" and thus the caliper pin bushings that that came in the brake kit didnt fit one caliper - one takes the "rings" bushing and the other has a long black silicone sleeve with flanges on both ends of the sleeve. The caliper with the long sleeve seems to be from a K3500. Yet the brake pads fit. Any one have an idea what is going on here ? Also, the brakes wore perfectly symmetrically on both calipers - however the presumed K3500 caliper was worn to squeelers and the other side had a lot of pad left, which suggests more caliper clamping force - yet I never noticed any pulling ever. Any ideas what is going on ? Or what that caliper is ? To make it right - thoughts on caliper upgrade ? JB6 C5S work truck cheyenne.

 

[Supercharged111]

Seems more likely that one of the calipers is stuck. And if the pads fit both calipers then it's not a K3500 caliper. You'd have to send the clip out to hold it in place in one of those. And the slider mechanism is the same between them both.

 

[REM777]

If I was going to make it right - is there a caliper upgrade you can suggest or am I already the best with what I got with the JB6 C5S RPO codes ? thanks

 

[1998_K1500_Sub]

If I was going to make it right - is there a caliper upgrade you can suggest or am I already the best with what I got with the JB6 C5S RPO codes ? thanks

You can change to larger diameter piston calipers IF you change the MC too.

Basically it’s a JB7 MC and caliper “upgrade”.

For more details, ask.

Or simply search for “86mm” on GMT400.

 

[Supercharged111]

You can change to larger diameter piston calipers IF you change the MC too.

Basically it’s a JB7 MC and caliper “upgrade”.

For more details, ask.

Or simply search for “86mm” on GMT400.

And rear wheel cylinders up a size or 2 to match.

 

[1998_K1500_Sub]

And rear wheel cylinders up a size or 2 to match.

^^^ this


@REM777, the stock JB6 11” drum cylinder is 1”, the largest 1.1875”, and there’s a third somewhere in between.

@Supercharged111, didn’t you recently make this mod? Maybe I’m hallucinating…

 

[Supercharged111]

^^^ this


@REM777, the stock JB6 11” drum cylinder is 1”, the largest 1.1875”, and there’s a third somewhere in between.

@Supercharged111, didn’t you recently make this mod? Maybe I’m hallucinating…

I did. My pedal is higher, tighter, and more responsive for it too.

 

[REM777]

I think I figured this out - from "1998_K1500_sub " - aka NitroJunkie's link in a prior post - the unknown caliper IS the 86 mm and also explains why the unequal pad wear - IE unequal pad clamping force.

Can this be used with the JB6 - C5S brake master - which I replaced in effort to shore up the spongy brakes ?

thank you guys !!

 

[Schurkey]

The smaller calipers are "Low Drag" units that require a third chamber in the master cylinder.

The 86mm calipers are not "Low Drag"; they don't need the third chamber, but they probably could use a two-chamber master cylinder of larger bore diameter.

Use the master cylinder that goes with the calipers, and as said--use larger-bore rear wheel cylinders.

 

[REM777]

Stupid question - has anyone ever quantified the low drag of the "low drag" caliper ? Is it almost none measurable ? thanks

BTW - NBS = new body style?

FYI-

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I used to work with a guy who was an engineer at GM on the GMT400 project - in relating engineering war stories of corporate incompetence's - he told me about the GM bidding process on this truck and the low bid failure of Kelsey Hayes on this brake system - particularly the low fidelity of the antiskid and the issue with wheel speed triggering the antiskid when driving over railroad tracks etc. He said was the worst brake design - but a low cost bidder - He also related that one of the caliper designs actually yield brake caliper piston force - as in spread during hard braking - I never really paid much attention to what he was haranguing about until I bought one of these. The other issue was the excellent cylinder head design with an incredibly lame camshaft and valvespring tension - was all low drag stuff ..