Six wheel discs, 1, 600 psi brake pressure front and rear

[Jim Hupy]

You should not need even 1/2 that much pressure to lock up the brakes on
your coach with your current set up. Are your pads and rotors well broken
in? Are you sure that your system is completely bled of all air? Your goal
should be to apply pressure to rotating tires, not stationary ones. Sliding
tires will flat spot them with some loss of control.
Jim Hupy
Salem, Or
78 GMC ROYALE 403.

> With Bob Stone's hydroboost kit using a 40mm master cylinder we were able
> to get 1,400 psi brake pressure. The limiting factor seemed to be available
> pressure from the steering pump. PSC sells a new Saginaw style pump made
> by Delphi that is supposed to output 1,650 psi. The PSC pump I installed did
> not quite do that until the relief part of the flow valve got tweaked.
> After that we were able to get 1,600 psi brake pressure with Sue on the
> pedal.
> We have Manny's reaction arms on the rear and were not able to drag any
> tire on concrete at 1,400 psi so more pressure should be more brake.
> Calipers
> are 80mm front and mid with 66mm Kelsey Hayes park brake on the rear.
> http://www.pscmotorsports.com/motorsport-specific-products/
> offroad/power-steering-pumps-kits-components/gm-chevy/80-
> newer-hi-performance-power-steering-pump-w-o-can.html
> http://www.gmcmhphotos.com/photos/power-level-valve-
> fitting/p61812-rear-brake-pressure.html
> http://www.gmcmhphotos.com/photos/power-level-valve-
> fitting/p61813-front-brake-pressure.html
> https://youtu.be/1BZdAva7wqc
> https://youtu.be/x7_mwmyEDaY
> --
> Wally Anderson
> Omaha NE
> 75 Glenbrook
> Megasquirt III injection
> Bob Stone hydroBOOOOST
> Manny reaction arm system
> Branscombe Kelsey Hayes park brake
> http://wallyandsue.blogspot.com/
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

 

[Ken H.]

Jim,

Huh? What kind of pads do you use to get GMC brakes, with any size
calipers, to lock up with that little pressure? I run Performance Friction
all the way around and have a front line pressure gauge on the dash so I
can compare deceleration rate with line pressure. Dependent upon road
surface, it generally takes 1000+ psi to reach incipient lockup. With Manny
Brakes, that condition occurs first on the front wheels.

Admittedly, I haven't done a lot of testing of this statement because I
haven't needed either that fast stopping, nor the flat spots that could so
easily occur. It might be that if they were hot, the PF's might be as
sticky as you imply.

Ken H.

> You should not need even 1/2 that much pressure to lock up the brakes on
> your coach with your current set up. Are your pads and rotors well broken
> in? Are you sure that your system is completely bled of all air? Your goal
> should be to apply pressure to rotating tires, not stationary ones. Sliding
> tires will flat spot them with some loss of control.
> Jim Hupy
> Salem, Or
> 78 GMC ROYALE 403.
>

>
> > With Bob Stone's hydroboost kit using a 40mm master cylinder we were able
> > to get 1,400 psi brake pressure. The limiting factor seemed to be
> available
> > pressure from the steering pump. PSC sells a new Saginaw style pump made
> > by Delphi that is supposed to output 1,650 psi. The PSC pump I installed
> did
> > not quite do that until the relief part of the flow valve got tweaked.
> > After that we were able to get 1,600 psi brake pressure with Sue on the
> > pedal.
> > We have Manny's reaction arms on the rear and were not able to drag any
> > tire on concrete at 1,400 psi so more pressure should be more brake.
> > Calipers
> > are 80mm front and mid with 66mm Kelsey Hayes park brake on the rear.
> > http://www.pscmotorsports.com/motorsport-specific-products/
> > offroad/power-steering-pumps-kits-components/gm-chevy/80-
> > newer-hi-performance-power-steering-pump-w-o-can.html
> > http://www.gmcmhphotos.com/photos/power-level-valve-
> > fitting/p61812-rear-brake-pressure.html
> > http://www.gmcmhphotos.com/photos/power-level-valve-
> > fitting/p61813-front-brake-pressure.html
> > https://youtu.be/1BZdAva7wqc
> > https://youtu.be/x7_mwmyEDaY
> > --
> > Wally Anderson
> > Omaha NE
> > 75 Glenbrook
> > Megasquirt III injection
> > Bob Stone hydroBOOOOST
> > Manny reaction arm system
> > Branscombe Kelsey Hayes park brake
> > http://wallyandsue.blogspot.com/
> >
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> >
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

 

[hal stclair]

I wonder how our steering boxes will like the increased pressure. It's pretty simple to up the flow and pressure on our pumps merely adding or
removing shims and increasing orifice sizes. I just don't know if the seals would live under 1650 lbs of fluid. It'll be curious to see.
Hal
--
1977 Royale 101348,

1977 Royale 101586, Diesel powered,

1974 Eagle Bus 45',w/slideout