To all those planning on a nbs master cylinder swap

Joe Wentland · Apr 20, 2018

beardeddummy said:
The nbs master cylinder is meant for rear disc. That being said if have rear drums they require a constant 10psi the obs master cylinder has a provision for this. The nbs mc does not. Yes it will work but you will no longer have rear brakes. On most of these trucks the back brakes dont work unless you adjust them. Anyways my boss a mechanic with over 20 years experience educated me on this and i figured it ought to be shared. Im not trying to say i know it all but i have learned when it comes to the mechanical side of things if he tells me that the sky is green i need to find a storm shelter

Joe Wentland · Apr 20, 2018

Hello there, sorry to bump such an old post! I'm going through the swap as well.. and found the my abs module as internally shot.. and I believe that abs unit is where the system is metered for the rears.. after deleting my abs module and installing an inline proportioning valve, and making sure the rears are adjusted, still have an odd pedal. So am I correct in thinking I need to add an inline residual pressure valve for 10 psi as well to have good brakes ?

Supercharged111 · Apr 22, 2018

This is news to me. I did the swap, pretty sure donor was a rear disc setup. Pedal feel was improved, better than adjusting brakes. Still not quite what I'm after so I think after reading this I'll revert to a GMT400 hydroboost MC that has the valving to keep that residual pressure on the shoes. FWIW I deleted my ABS as well and just tossed on a junkyard fresh TBI rear proportioning valve. I think a custom setup would be better though as the rears on the lighter trucks are a bit under proportioned.

shamrock246 · May 3, 2018

Supercharged111 said:
This is news to me. I did the swap, pretty sure donor was a rear disc setup. Pedal feel was improved, better than adjusting brakes. Still not quite what I'm after so I think after reading this I'll revert to a GMT400 hydroboost MC that has the valving to keep that residual pressure on the shoes. FWIW I deleted my ABS as well and just tossed on a junkyard fresh TBI rear proportioning valve. I think a custom setup would be better though as the rears on the lighter trucks are a bit under proportioned.

Where is the residual pressure valve on the hydroboost master? I didn't see one when I did my upgrade.

CW73 · Oct 25, 2019

shamrock246 said:
Where is the residual pressure valve on the hydroboost master? I didn't see one when I did my upgrade.

For anyone reading this.. the RESIDUAL valve is NOT in the master cylinder. It's in the combination valve, located on the side of the ABS module if you have one or in the brake proportioning/combo valve below the master cylinder. When swapping to NBS MC with rear drums you will still have a drum residual valve. When converting to rear disc you must remove the seal on the residual valve so your rear calipers dont drag.

To all those planning on a nbs master cylinder swap

Joe Wentland

Newbie

Joe Wentland

Newbie

Supercharged111

Truly Awesome

shamrock246

I'm Awesome

CW73

Newbie

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