JB6 Brake Upgrade

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skiderjr

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Hey guys, doing a restoration on my 1994 extended cab, step side. I have installed the nbs master cylinder, as at one time, that seemed to be what would help with the soft petal on these trucks. Reading through the forums, I see various opinions, on how these brakes should be setup. Should I stay with the original master cylinder, or stay with the nbs master cylinder? Also, what other upgrades should I do, to the brakes? Will updating the drums, on the rear to disk, allow the new nbs master cylinder, to work properly. Just want to upgrade the brake system, to what will work properly.Thanks
 

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1998_K1500_Sub

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Hey guys, doing a restoration on my 1994 extended cab, step side. I have installed the nbs master cylinder, as at one time, that seemed to be what would help with the soft petal on these trucks. Reading through the forums, I see various opinions, on how these brakes should be setup. Should I stay with the original master cylinder, or stay with the nbs master cylinder? Also, what other upgrades should I do, to the brakes? Will updating the drums, on the rear to disk, allow the new nbs master cylinder, to work properly. Just want to upgrade the brake system, to what will work properly.Thanks

What rear brakes do you have already? Do you already have JB6 or considering a JB6 upgrade from JB5 (to 11" drums)?

I know the quick-take-up / low-drag systems can work reasonably well, but on account of the uncertainty of the JB5/JB6 replacement calipers out there (are they really built for low-drag or aren't they? See attached.) I prefer to side-step the entire matter and use the "regular" brakes that came on the JB7/JB8. Too, the JB6 brakes on my Suburban never worked well, so I'm jaded.

The NBS MC is a non-quick-take-up design, as are the GMT400 JB7/JB8 MCs.

The JB7/JB8 calipers are a non-low-drag design, appropriate for the non-quick-take-up MCs.

Although the NBS has a larger bore (~1.34"/34mm) than the typical JB7/JB8 (1.25" for HD / 1.125" for vacuum boost, I believe) and thus seemingly puts you at a bit of a disadvantage, the JB7/JB8 calipers with their larger bore (3.15"/80mm and 3.385"/86mm bores are available) will offset the disadvantage almost completely, relative to the stock JB6 caliper (3"/76mm).

I've got the NBS MC on my K1500 Suburban, 3.15" JB7 calipers in front (vs. 3" OE) and 1.1875" slave cylinders in the back (vs. 1" OE) on 11" OE drums. The Suburban weighs about 6200# across the scales almost evenly distributed F/R. The brakes work very well IMHO, MUCH better than they ever did for as long as I've had it; the brake pedal moves without any resistance until the brakes engage and then it's VERY firm, and the brakes very responsive IMHO (perhaps not like a BMW, that's a different class of machine). I've SS hoses F/R as well, which contributes to the firm pedal.

Since you have the NBS master, I would not encourage you to replace it. If you were starting from scratch, I would suggest the GMT400 non-quick-take up MC used on the heavier trucks.

I made some comments about the rear disc setups elsewhere in some recent threads; I'll post a link. Different people view them differently.

(edit) See


and


This one is good too:

 

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1998_K1500_Sub

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Thanks for the reply guys! I currently have JB6 brakes, with the 11.15" drums in the back. I also did remove the abs system as well.

Since you already have the NBS installed, you don't have much left to do, e.g.,

- front calipers; either of the larger sizes mentioned earlier are appropriate

- if desired, the rear slave cylinders; there are two choices, the OE is 1", the largest is 1.1875", and I believe there's a 1.1" (check specs on RockAuto for reference)

- if desired, SS hoses; match the vehicles existing fittings, e.g., SAE or metric

:waytogo:
 
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L31MaxExpress

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Biggest improvement is hydroboost. My 6,500 lbs Express van would rearrange your neck and nearly face plant your face into the steering wheel at 70 mph with hydroboost, 1 ton master,1 ton SRW front calipers and the stock rear drums. Shortly after I had swapped the brake setup to that, I was cruising along at 75 mph in the fast lane and had a car dart over from an on ramp at 45-50 mph right in front of me. I went full on panic stop on the pedal and proceeded to re-arrange everything in the van including nearly smacking the steering wheel with my face. It knocked the console that holds the TV out of its mounting on the floor. ABS kicked in at 75 mph and it shut down right then. If I had still been running the vacuum boost, my front bumper would have been in that guys back seat. The stock brakes on my van sucked, should have come with hydroboost from the factory. It went from terrible to sports car like stopping.

I converted my 83 G20 to rear discs about 20 years ago using Impala SS parts. The rear discs were not a massive improvement that they are always talked up to be. The hydroboost swap was a big improvement on that van as well.
 
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Schurkey

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MOST rear disc brake conversions (not all) will be a DOWNGRADE from the 11.x JB6 rear drums. Cheap junk with poor engineering.

Be VERY CAREFUL picking out a disc brake system. An OEM system including the park brake from a newer truck of at least the same GVWR as your truck is strongly recommended if you just gotta have discs in back. I think they're way more trouble than they're worth if you already have the JB6 rear drums.
 

Das Hatt

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In the quest for a firmer brake pedal on my 92 C1500 RCLB i have completed the following at separate times: remove ABS, replace rubber hoses with SS braided hoses, rebuilt factory 10" drum brakes (new AC Delco cylinders, Duralast shoes, and AC Delco hardware).

By far the biggest difference in pedal feel was rebuilding the drum brakes. So you might not necessarily need to do some conversion if just refreshing what you have will accomplish your goals.
 

Vic327

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On my C1500 suburban which started as JB6 I used a mix of parts. I have a MC from a 1978 truck that is straight 1.125", the front calipers are the 2500 8200# larger bore and to keep the balance I put 1 1/16" rear wheel cylinders. This combo worked well for me including braided brake lines. The adjustment on the drums with good pads and shoes are the best place to start. These trucks are getting old make sure your calipers pins are not corroded.
 
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