rear brake proportioning

[RThompson]

Haven't neen able to locate a rear brake load sensing valve. 4 wheel discs are great but I think they would be greatly improved if the rear brakes clyinders were operating with higher psi when carrying a heavy load. I understand why manufactures of these trucks want to keep the rear end from locking up when they are running empty, but my rear brakes are just not doing enough work when towing. This is particularly obvious when the trailer weight transfers on to the truck when braking hard. Recently completed 9,000 mile trip towing 7000 lb. fifth wheel and the rear wheels at the end of the trip showed very little dusting while the front wheels were deep red from brake pad dust. Any ideas out there about adjusting rear psi for loaded conditions.

 

[RThompson]

Anyone have 2002 manual that can look up proportioning valve or height sensing valve and see if there is an adjustment somewhere that will help with rear braking under load? Some of the manufacturers use to put a sensor linked to axle housing to assist in giving rear brakes more pressure as the load was increased. Can't see anything like that on this truck though. Any help on this would be much appreciated. .

 

[BK]

if you have a load sensing valve, it's connected to the rear axle by a rod. That rod goes up to the frame to the valve... the valve has the brake hard line going into it and coming out of it, at some point the hardline is changed over to the rubber line that goes down to the axle.



So either follow the hose up from the axle to the frame and along the frame or look for a rod that's attached to the axle and heads up to the frame.



From what I know, and I'm not sure about this... but with the rear disks, you maynot have the load sensing valve.



hope this helps...

 

[dan_gilson]

The only way that I know of to get more pressure to an axle is to use a dual master cylinder. That is what the race cars use. Each master has an adjustment on an independannt plunger.



A proportioning valve DOES NOT adjust pressure. It adjusts flow to a area. In this case the rear axle. It slows down the rate that fluid flows to that axle.

 

[Mick2500]

RT,

The load sensor was part of the old RWAL system.

Our 4-wheel disc with ABS does not have the

load sensor stuff.

I also believe there is no proportioning valve on our trucks with 4-wheel discs. None mentioned the manual.



Mick

 

[RThompson]

Mick,,





The load sensor was part of the old RWAL system.

Our 4-wheel disc with ABS does not have the

load sensor stuff.

I also believe there is no proportioning valve on our trucks with 4-wheel discs. None mentioned the manual



Thanks for looking that up.







RThompson

 

[fest3er]

Originally posted by RThompson
Mick,,


The load sensor was part of the old RWAL system.
Our 4-wheel disc with ABS does not have the
load sensor stuff.
I also believe there is no proportioning valve on our trucks with 4-wheel discs. None mentioned the manual

Thanks for looking that up.



RThompson

I believe the reasoning for removing the height-sensing valve was that the ABS could do as good as or better than the valve in controlling the rear braking effort. So you should have maximum cylinder pressure loaded or unloaded.

Fest3er

 

[MidwestMotorman]

flipe side

Rather than thinking your rear brakes are not braking enough, look at it that your front brakes are braking too much. Probably or possibly dragging. Pull those calipers and pins. Lube the pins and the caliper mounts with some anti-seize. You could also do this to the rear brake setup to prevent the same condition that all of us see with our front disc brakes.