C-20 brakes with adjustable proportional valve - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Andy4639 · 11-15-2020, 03:34 PM

I have the Ramp truck front disc all done. Truck stops great but was wondering about the valve. Just wondering how it works. Should it be turned in to get more pressure and less flow are should it be turned out to get more flow and less pressure????
When we set it up there are 11 full turns from all the way out to full in. It's set at 9 turns in now from my notes I have.

What is the knee effect that is always talked about?

No it's not factory routed. I told him to do it as easy as he could.

Master cylinder is front bowl is rear drums & back bowl is front disc. Lines run to adjustable proportional valve and the 2 front disc lines out to brakes and one line to rear drum's.

geunther · 11-15-2020, 05:21 PM

Clockwise, increasing pressure will bias the brakes more to the rear relative to where you have it now. I adjust on a gravel road, applying the brakes fairly hard, keep applying pressure (increase on the knob) until the rear locks up too soon for you liking. You probably already know, but the adjustable portion of the valve only affects the rear brakes.

Andy4639 · 11-15-2020, 06:17 PM

Quote:

Originally Posted by geunther

Clockwise, increasing pressure will bias the brakes more to the rear relative to where you have it now. I adjust on a gravel road, applying the brakes fairly hard, keep applying pressure (increase on the knob) until the rear locks up too soon for you liking. You probably already know, but the adjustable portion of the valve only affects the rear brakes.

Yes it only effects the rear. So gravel road is best to do said adjusting. Adjust until the backs lock up and then turn it back a little I guess.

Thanks for the info.

geunther · 11-15-2020, 07:24 PM

If they "just" lock on a gravel road, you really do not need to turn back. On pavement the rolling friction will be higher and should be just about set right. But the beauty is, you can fine tune very easily. I have a similar setup on a CJ7 and once I had it set, I never had to adjust it again.

Being a C-20, if you haul heavy from time to time, you can certainly apply more rear bias when you are heavy with just a 1/2 twist or so.

Andy4639 · 11-15-2020, 07:44 PM

Got it, thanks. Yea I don't haul much with it but I have before. I've carried light loads and heavy loads.

**Boog** · 11-16-2020, 12:33 AM

Andy may I suggest do your hard braking test in a wet parking lot? Wet roads are where you really don't want the rear end coming around on you while doing hard braking.

Andy4639 · 11-16-2020, 10:31 AM

Quote:

Originally Posted by Boog

Andy may I suggest do your hard braking test in a wet parking lot? Wet roads are where you really don't want the rear end coming around on you while doing hard braking.

That's a good idea to!

Andy4639 · 11-16-2020, 08:32 PM

I drove the truck several times it stops just fine but if I do decide to adjust them I will do it on gravel then try it out on a wet road also.

11-15-2020, 03:34 PM	#1
Andy4639 Old member Join Date: Jan 2002 Location: Liberty, & Garden City S.C. , U.S. Posts: 19,936	C-20 brakes with adjustable proportional valve I have the Ramp truck front disc all done. Truck stops great but was wondering about the valve. Just wondering how it works. Should it be turned in to get more pressure and less flow are should it be turned out to get more flow and less pressure???? When we set it up there are 11 full turns from all the way out to full in. It's set at 9 turns in now from my notes I have. What is the knee effect that is always talked about? No it's not factory routed. I told him to do it as easy as he could. Master cylinder is front bowl is rear drums & back bowl is front disc. Lines run to adjustable proportional valve and the 2 front disc lines out to brakes and one line to rear drum's. Attached Images __________________ 1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs.

11-15-2020, 05:21 PM	#2
geunther Registered User Join Date: Apr 2005 Location: Cheyenne, WY Posts: 742	Re: C-20 brakes with adjustable proportional valve Clockwise, increasing pressure will bias the brakes more to the rear relative to where you have it now. I adjust on a gravel road, applying the brakes fairly hard, keep applying pressure (increase on the knob) until the rear locks up too soon for you liking. You probably already know, but the adjustable portion of the valve only affects the rear brakes.

11-15-2020, 07:24 PM	#4
geunther Registered User Join Date: Apr 2005 Location: Cheyenne, WY Posts: 742	Re: C-20 brakes with adjustable proportional valve If they "just" lock on a gravel road, you really do not need to turn back. On pavement the rolling friction will be higher and should be just about set right. But the beauty is, you can fine tune very easily. I have a similar setup on a CJ7 and once I had it set, I never had to adjust it again. Being a C-20, if you haul heavy from time to time, you can certainly apply more rear bias when you are heavy with just a 1/2 twist or so.

11-15-2020, 07:44 PM	#5
Andy4639 Old member Join Date: Jan 2002 Location: Liberty, & Garden City S.C. , U.S. Posts: 19,936	Re: C-20 brakes with adjustable proportional valve Got it, thanks. Yea I don't haul much with it but I have before. I've carried light loads and heavy loads. Attached Images __________________ 1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs.

11-16-2020, 12:33 AM	#6
Boog laying low Join Date: Mar 2001 Location: Searcy, Ark. USA Posts: 12,957	Re: C-20 brakes with adjustable proportional valve Andy may I suggest do your hard braking test in a wet parking lot? Wet roads are where you really don't want the rear end coming around on you while doing hard braking. __________________ Boog 69 Chevy stepside, 358/T350, 4.11 posi, 4.5/4 drop, rallys, poboy driver primer is finer 91 Chevy sportside, Tahoe, Yukon & GMC Crewcab All GM..'nuff said. I stand for the flag and kneel at the cross

11-16-2020, 08:32 PM	#8
Andy4639 Old member Join Date: Jan 2002 Location: Liberty, & Garden City S.C. , U.S. Posts: 19,936	Re: C-20 brakes with adjustable proportional valve I drove the truck several times it stops just fine but if I do decide to adjust them I will do it on gravel then try it out on a wet road also. __________________ 1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs.



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