First hand experience with changing to the NBS master cylinder WOW!

[95 Silv]

I did this today! Had uneven front pad wear due to a bad front, left caliper and was the perfect chance to do this while I was at it. Thanks Speedy for the write up process with part #'s. Made finding the right parts so much easier. Definitely feel the pedal difference but like you still have to press hard. Might bleed again just to be sure but really impressed with this mod.

[95 S_Trucker]

Does anybody know what master cyl. to use on a hydroboost truck? I would love to do something like this on my 99.

[Tom]

Originally Posted by 95 S_Trucker

Does anybody know what master cyl. to use on a hydroboost truck? I would love to do something like this on my 99.

If you have hydroboost then there is nothing to be done, you already have as firm a brake pedal as you can get. If people do this MC swap and still don't like the feel then hydroboost is the last option to try, and your already there.

[speedygonzales]

couldn't resist. These were bought on a steal from Summit. I couldn't resist. With the slotted rotors. Hot damn.

[burkey05]

found this on the summit website

looks like SSBC might read this forum too. lol

http://www.summitracing.com/parts/ss...mc/model/c1500

[Keith Seymore]

Originally Posted by burkey05

found this on the summit website

looks like SSBC might read this forum too. lol

http://www.summitracing.com/parts/ss...mc/model/c1500

$223? Ouch!

I think I paid around $70 for mine.

K

[speedygonzales]

Screw SSBC for $220 I got mine at Advance for $75. Don't forget, if you pay online then pick up the item at the store, you save. I saved $10 on my MC.

[t_graham11]

I did some searching and the new cylinder is 1.8" and the original is 1.6" so you'll have to bore out the .2" on hydro boosted trucks. Some guys have said they did it them selfs but I'm going to buy a new hydro boost and get the machine ship to bore it out for me.

I ha a leaky slave cylinder and my pedal went dead changed it and then just yesterday I had zero pedal again and was standing on the brakes when I pulled into my house, luckily I just rubbed the wheel against the retaining wall rather than through my carport. My brake fluid is really dirty, I heard that was because the MC seals were rotten. I'm pretty excited to have a firm pedal again
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[DZL1]

No pics of your mod installed?

DZL1.

[400sbctruck]

Thank-You!!! Awesome thread, I have driven many of these trucks, and this always bothered me.

This WILL happen ASA I need another M/C.

Curious about the NBS 13" vs slotted replacement(I can drill
And/or slot at work).

[speedygonzales]

Ok I have JB5 system and lookup says they are 6400 Lb.
Here's a picture
http://i1371.photobucket.com/albums/...g?t=1403961476

Only thing I see is the "DA" sticker. So what do I have? And how do you figure it out? I didn't see anything that explains the types of diaphragms. How does the types relate to the RPO code?

I see JB8 says 10000 Lb That must be Hydraulic.

I found this on a bulletin board
JB5= front disc 11.86X1.29 rear drum 11.15X2.75 Vacuum-Double Diaphragm

JB7= front disc 12.50X1.54 rear drum 13.00X2.50 Vacuum-Double Diaphragm

JB8= front disc 12.50X1.54 rear drum 13.00X3.50 Hydraulic-Hydro-Boost

But how do you get part numbers for these boosters.

Then there is this:
http://www.oreillyauto.com/site/c/de...1305&ppt=C0066

It says it's 10.75" and used for JB5,6&7???? I don't get it.

Do I want the one that is 13" x 2.5? Do you look for the booster from a 1 ton truck?

[CDR]

Hey Speedy

I have JB6 brakes and believe I have the single diaphragm booster...With an HA sticker on it

Vacuum-boosted:
JB5 = Power Brakes, Disc/Drum, 6,400 lb
JB6 = Power Brakes, Disc/Drum, 7,200 lb
JB7 = Power Brakes, Disc/Drum, 8,400 lb
JB8 = Power Brakes, Disc/Drum, 10,000 lb

Hyrdaulic-boosted:
JD5 = Dual Power Brakes, Disc/Drum, 6,400 lb
JD6 = Hydraulic Power Brakes, Disc/Drum, 7,200 lb
JD7 = Hydraulic Power Brakes, Disc/Drum, 8,400 lb
JF9 = Hydraulic Power Brakes, 4-Wheel Discs

I believe the JB7 called for the larger DD booster you linked to. There is also a SMALLER DD booster available... Is that what you have on your JB5's?

[El conquistador]

Just did this on my truck and the results were great. After I did it though, I was doing some reading online and the "store bought" version of this upgrade from SSBC shows the adapter going in the rear port and reversing the brake lines.
http://www.summitracing.com/parts/ssb-a0463

instructions...
http://ssbrakes.com/attachment/63706...ction%20Manual

Any ideas?

[CDR]

You may be referring to the design change on the NBS brake circuits being flipped F/R?

With our trucks using the step bore master the front circuit had to use the forward portion of the cylinder to drill the stepped bore ( can't put a bigger bore bit thru a smaller bore hole)

Since the nbs uses the same bore size for both circuits, the engineers chose to reverse the layout, but they should operate identically.

[El conquistador]

Originally Posted by CDR

You may be referring to the design change on the NBS brake circuits being flipped F/R?

With our trucks using the step bore master the front circuit had to use the forward portion of the cylinder to drill the stepped bore ( can't put a bigger bore bit thru a smaller bore hole)

Since the nbs uses the same bore size for both circuits, the engineers chose to reverse the layout, but they should operate identically.

So the "store bought" instructions just flip flop the lines to match the front and back of the NBS master cylinder, even though there is no difference in the performance in the front and back.

[Keith Seymore]

Originally Posted by t_graham11

I did some searching and the new cylinder is 1.8" and the original is 1.6" so you'll have to bore out the .2" on hydro boosted trucks. Some guys have said they did it them selfs but I'm going to buy a new hydro boost and get the machine ship to bore it out for me.

I'm not sure I'm following you -

Are you talking about boring out the center bore of the master cylinder (affecting line pressure)? or are you talking about the outside diameter of the hub that fits into the brake booster?

K

[t_graham11]

Me? No I just ended up buying the two MC's the new body's type and te stick one for my truck. I'm putting the stock one in today and I'm going to buy a new hydro boost next month and get it machined out that way I'll have the parts on hand next time I need to do the brakes ill swap out the new mc and hydro boost.

**i don't know if in allowed to post outside links**

But here is the write up I found.... http://www.fullsizechevy.com/forum/g...r-project.html
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[t_graham11]

Yeah the outside diameter of the nbs master is .2" larger diameter so you need to bore out where is slips inside for the plunger to push.

It'll be a while but I'll take pictures of everything and give a good explanation
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[Keith Seymore]

Originally Posted by t_graham11

Yeah the outside diameter of the nbs master is .2" larger diameter so you need to bore out where is slips inside for the plunger to push.

It'll be a while but I'll take pictures of everything and give a good explanation
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Ok - thank you. Understood.

There were a couple different sizes used in that area; they also varied based on Quick Take up vs Non quick take up master cylinders.

K

[Mickeymotormount]

Finally did this swap myself on my '93 Extended Cab Long bed 1500 4X4. Pedal feel was definitely higher/harder. But I feel that it still takes a firm push to achieve any kind of decent stopping power. Even with new rotors, 1 ton calipers and pads, new rear wheel cylinders and flex lines. I might have to upgrade to hydro boost next.

[speedygonzales]

Mickey, why don't you try a manually adjustable proportioning valve before you do anything else?

[Mickeymotormount]

Thanks for the reply, Speedy. I must say, your "Pride and Joy" is beautiful. For me, someday........ in a dream.........


My truck already has the 14 bolt rear(light duty 3/4ton), which has larger brakes than the 10 bolt rear. This was standard on my vehicle which has RPO code F44(heavy duty chassis). I thought about changing to an adjustable proportioning valve, but since my truck needed new front hardware/rotors, I figured I would go this route. I have read much here about the upgrade to bigger calipers and the NBS master cylinder. It definitely seemed like the right approach. My rear brakes are about to the point of locking up before the fronts do with the NBS master cylinder so I figured I'm close with the proportioning aspect of the brakes.

[speedygonzales]

Well let's relate what I read about the rear disc conversion to your situation. The disc conversion needs more pressure than the drums. So the kits usually have a new MC.

Now let's look at your set up. You have larger, MUCH larger front calipers and larger rear wheel cylinders. I think you aren't getting enough pressure. You should get the gauge kit and check each location for it's pressure.

[t_graham11]

Mickey, I think your going through the same problem as I am. I have a SAS and the front brakes rotors and calipers were upgraded (I'll have to look at my records to know to what exactly) my rear end felt like it was doing all the stopping and it got so bad that the brake cylinders began to leak. I put in a proportioning valve and the front is doing most the work.

I'm getting the hydro boost bored out and will be switch to the new mc soon, I just replaced the original mc and I still get a spongy brake, happen to me a couple times where it's gone to the floor. Ill gravity bleed tonight to see if that helps
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[Mickeymotormount]

Links come up for me as well.