How to: NBS master cylinder swap for firm brake pedal

[Nak]

Sorry man, I totally misunderstood. Never post tired... I was commenting on swapping to a NBS MC for brake feel. My bad. Anyways, absolutely different for an off road machine as opposed to a DD.

I looked at the SSBC website. They list the same MC for disc/disc and disc/drum? So these can't have a residual pressure valve built in. They do sell those as well, so you probably want to consider adding one of those if you go with this type of MC with disc/drum.

 

[bowtiefreak]

No problem, confusion happens

Yeah or even just adding a proportioning valve on the rear line.

I see many guys getting into trouble when swapping for larger calipers and things like that too. So many mixed reviews out there. I started yet another thread that people will hopefully just post result good or bad about the swap

 

[SunlitComet]

Bowtie, I don't have one far sure but I think they claim firm feel because they don't have the internal valve like the obs mc quick take up feature which lets the pedal sink a bit and the fact that it may apply the drums sooner instead of letting them apply differently. That coupled with the fact that the physical volume in the hydraulic system has change with no change in the proportional valve is how they get there claim i believe. In short unless you get a rear disc setup with all the parts on mods included from someone like summit or ssbc do not bother with just the mc. Convert booster and mc to an obs jb6 configuration. just make sure loose items in the cab are tied down.

 

[bowtiefreak]

My suburban has the JB6 brakes already. Is it possible that the wrong master is on it?
My Tahoe has the JB5 brakes. Shame on me but I thought the difference was only the drum diameter. Please correct me if I am wrong as this would be a big problem is the MC is incorrect. So is there a difference in the JB5 and JB6 master cylinder??

Would a JB7 Master Cylinder fit?
Is there an upgrade on the rear wheel cylinders? I read you can upgrade the 14SF axles with larger bore cylinders but noting about the smaller set ups.

I can try multiple things. Temped to upgrade the burban to disc and put the 11" drums on the Tahoe to replace the 10" set up.

 

[Nak]

The JB6 and the JB5 brakes use the same MC. The only difference between the two is the size and type of rear drum, and the combination valve. It's possible the factory used the wrong C-valve. That's why I was trying to find out about your brake balance. The JB7 brakes used a different C-valve than the JB6, and in fact there is a Service Bulletin requiring the JB7 brakes to get rid of the C-valve and use the C-valve from the JB6 brakes. The original JB7 C-valve limited brake pressure to the rears far more than it should have. I think I read it had an 85/15 ratio front to rear? This led to poor brakes and fast front brake wear. Anyways, if your rig has always had bad brakes, it might be the JB7 C-valve was installed by mistake. The only visible difference between the two is a sticker. The good news is that the proper C-valve is still available new. I saw it on Amazon for around $120 I think?

 

[bowtiefreak]

Here's another one to ponder. The SSBC firm feel master calls to have the brakes lines switched from the factory positions (front to rear, rear to front). Why would that be?

http://ssbrakes.com/attachment/63706-Instruction Manual

 

[Nak]

??? That makes no sense. If the MC is designed for disc/disc, it should have two identical size bores. The only reason you'd have to reverse the lines is if the residual pressure valve was in the front, but if it has a residual pressure valve then it would be no good for disc/disc brakes. If it does have a residual pressure valve, it's clearly designed for drum brakes, but with two equal sized bores. I'm pretty sure the page you linked to specified the MC was good for disc/disc or disc/drum? Of course, that makes this pretty undesirable anyways. An MC really needs to be specified for one or the other. I'm very curious to hear the explanation for such an odd setup.

 

[benblaquetahoe]

is that master cyl the same as police version? will installing the police version masterly/ booster/ calibers give my LT better braking?? and will they just swap?

 

[Johnny Racer]

Wow am I late to the party.

 

[hawgnutts]

The JB6 and the JB5 brakes use the same MC. The only difference between the two is the size and type of rear drum, and the combination valve. It's possible the factory used the wrong C-valve. That's why I was trying to find out about your brake balance. The JB7 brakes used a different C-valve than the JB6, and in fact there is a Service Bulletin requiring the JB7 brakes to get rid of the C-valve and use the C-valve from the JB6 brakes. The original JB7 C-valve limited brake pressure to the rears far more than it should have. I think I read it had an 85/15 ratio front to rear? This led to poor brakes and fast front brake wear. Anyways, if your rig has always had bad brakes, it might be the JB7 C-valve was installed by mistake. The only visible difference between the two is a sticker. The good news is that the proper C-valve is still available new. I saw it on Amazon for around $120 I think?

Hi Nak I've been following this thread today & I'm installing a '98 14-bolt SF w/TSM disc kit on my 95 Tahoe w/stainless braided lines front & rear. You guys spent a lot of time on disc/drum large & small but not much specific to disc/disc. Only that the NBS M/C was for that setup. In my case would that NBS master cylinder be a better fix since I'm going to 4-wheel disc? Would I need to change the hydravac booster? Would the ABS need to have the prop/comb valve changed out?