K1500 JB5 to JB7 upgrade brake parts

[Hewsty]

I know this may have been discussed many times here, but I can’t seem to find an answer to all the parts needed. I know the jb7 calibers and cylinders will bolt up to the jb5 mounting system and the jb5 cylinders will work with the back jb5 back drum system, but what I can’t find is will the front brake lines, front rotors, and pads from the jb5 system work with the jb7 calibers? Or will all that need to be changed over to the JB7 parts as well? I already did the JB7 nbs MC and the steel braided brake lines. I have jb7 calipers and cylinder picked out. I just need to know which rotors and pads to buy. Any help and advice is greatly appreciated!

 

[Caman96]

You’d get a more informed response by posting what vehicle you’re working on. Just curious, why do you need JB7 upgrade?

 

[GoToGuy]

It's a caliper. It's not a mounting size. It's a brake specification. Mount the caliper and measure the radius that will determine which rotor size you can use.

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[Hewsty]

O ya sorry I have a 94 k1500 with 5.7 motor. it’s an extended cab with a step side bed. The reason I’m looking to do the jb7 upgrade is for stoping power. I changed the master cylinder to the nbs to fix the soft break petal. The petal feels great but it quickly gets rock hard, doesn’t what to stop quickly, and has like a 2”-4” travel before the brakes engage. ( it had the petal travel before the nbs Mc upgrade unless I double pumped The petal) looking it up on this site I found it’s because the jb5 and jb6 MC and front calipers are low drag. The jb7/jb8 were conventional mc and calipers. But now that I have the jb7 nbs Mc and the jb5 calipers it makes my petal hard to push and doesn’t “squeeze” the front rotors as hard because it’s just using the smaller jb5 inter caliper piston because the jb7 Mc doesn’t have the quick take up valve. I think I got that all right. I been reading up about this for like 5-6 hours now hahaha.

 

[GoToGuy]

This same issue has been discussed before. Lots of things can mix and match and work together. But the brakes is some thing you should be more cautious. And you made the same mistake others have.

 

[Hewsty]

This same issue has been discussed before. Lots of things can mix and match and work together. But the brakes is some thing you should be more cautious. And you made the same mistake others have.

Agreed! I just fallowed the crowd with the nbs Mc upgrade without doing extra research. That being said the old obs mc sucked and the nbs is a definite upgrade I just trying to take it a step further and upgrade the rest of the system as well. The truck is safe to drive and is better then before it’s just not to my liking yet.

 

[Schurkey]

JB7 requires bigger rotors that won't fit your steering knuckle, and bigger rear drums that won't fit your backing plates. Backing plates suitable for JB7 on an 8.5" ring-gear axle probably don't exist.

The JB7 calipers can be mounted to your steering knuckle, and use the existing smaller rotors, if you're careful about pad-to-rotor clearance. The '7 calipers have much bigger pistons than the '5 calipers, should provide stronger clamping force.

The JB7 drums are HUGE compared to the hateful 254mm (10") leading-trailing shoe drums of the JB5 system. Getting rid of the JB5 rear drums is the best upgrade you can make, but doesn't replace a proper brake-fluid bleed/flush, or fixing actual faults/failures.

Your "NBS" master cylinder needs to GO.

When this was me, I upgraded to JB6 rather than JB7. Much easier, much less expensive since it's exactly the same as what you had/have already in front and at the booster/master; but differs in the rear.

Put the correct master cylinder back on. Bleed the ABS with a scan tool. Upgrade the rear brakes to the 11.x Duo-Servo units instead of that craptastic 254mm Leading-Trailing shoe system. A properly-functioning JB6 is all you need.

 

[Supercharged111]

. . . A properly-functioning HYDROBOOSTED JB6 is all you need.

I've kicked the idea around of going back to stock JB5/6 calipers and a JB6 master in my 1500. Currently it has the JB7 calipers and JB7 master. The pad fitment is quirky with that setup as you alluded to. But as is is overwhelmingly superior to vacuum boosted NBS master cylinder. There is just no comparison.

 

[Schurkey]

I waffle back and forth on Hydroboost upgrades. Hydroboost is more-powerful, but it also "feels" weird to me. Maybe that's just the two or three vehicles I've driven (and only one I've owned) with Hydroboost, compared to thousands I've driven with vacuum boost.

The JN3 booster is total crap. The JN/JB5 or 6 vacuum booster seems much more robust.

JB5/6 booster, left. JN3 "pancake" booster, right.

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[RacerM95]

Hydroboost on a C1500 ? hrmmm