Back brakes lock up to easy! - The 1947 - Present Chevrolet & GMC Truck Message Board Network

1965 C-10 · 02-20-2001, 02:48 AM

The truck has all new drums, wheel cylinders, shoes, bled properly, but if I hit the brakes kinda hard, the back wheels lock up, and the truck just keeps sliding down the road with people looking at me thinking what's up with this guy? I want to switch to front discs oneday, but if there is any kind of part that anyone knows of, I will just stick with drums for now, someone told me a proportioning valve would do the trick, has anyone else tried this?

Mongo · 02-20-2001, 08:24 AM

when I drove my 66 home from the guy I bought it from it was doing the same thing come to find out both of the lines to the front drums were compleety crimped. makes me wounder how many years it had been like that I think that was proboly why the truck had front end dammage.

rmfulton · 02-20-2001, 05:33 PM

Had this problem with an off brand 1953 with drums at all 4 corners. You need to make sure that the shoes and drums are clean of all contaminents (brake fluid, grease, etc.). If they are clean, then you need to adjust the star wheel so that wheels lock up in appropriate order. Usually, the front wheels are adjusted tighter than the rears.

Mick
1965 C-10 LWB, Fleet

1965 C-10 · 02-21-2001, 12:34 AM

Yes the brakes are all clean, no brake fluid or gear oil, and I have the star wheels adjusted so the drums will turn with a small amount of effort, also I have been told since it is a shortbed fleetside, that there is not enough weight in the back of the truck, but I had a small block chevy engine complete riding just in front of the tailgate, and it still did it.

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1972K10 · 06-04-2001, 03:40 PM

Look at the backing plates very carefully where the shoes rub against it. I had the same problem on my 1972 K10 and there were grooves worn into the backing plate where the shoes rub. I filled them up with weld and very carefully ground them back down smooth. Problem was gone. I had previous to this tryed new proportioning valve and bleeding several times to no avail. Start looking for grooved backing plates. Shoes need a smooth surface to rub against to work properly.

c-10 racer · 06-06-2001, 08:38 PM

do those trucks have a metering (hold-off) valve. i'd look into that... it is supposed to hold the brake pressure from getting to the rear wheels until the fronts have build up good pressure... most 4 wheel drum vehicles have one

02-20-2001, 02:48 AM	#1
1965 C-10 Registered User Join Date: Feb 2001 Location: Vacaville, Ca U.S.A. Posts: 52	Back brakes lock up to easy! The truck has all new drums, wheel cylinders, shoes, bled properly, but if I hit the brakes kinda hard, the back wheels lock up, and the truck just keeps sliding down the road with people looking at me thinking what's up with this guy? I want to switch to front discs oneday, but if there is any kind of part that anyone knows of, I will just stick with drums for now, someone told me a proportioning valve would do the trick, has anyone else tried this? __________________ 1965 Chevy C-10 shortbed fleetside, 327,th350,3.73 to 1

02-20-2001, 08:24 AM	#2
Mongo YES_____NO Join Date: Jul 1999 Location: Somewhere in the vicinity of betelgeuse Posts: 7,351	when I drove my 66 home from the guy I bought it from it was doing the same thing come to find out both of the lines to the front drums were compleety crimped. makes me wounder how many years it had been like that I think that was proboly why the truck had front end dammage. __________________ People many not remember what you said or what you did, but they will remember the way you made them feel. - unknown Cause, remember: no matter where you go... there you are. - Buckaroo Banzai 1984 Help support the board

02-20-2001, 05:33 PM	#3
rmfulton Registered User Join Date: Nov 2000 Location: Lansing, Michigan Posts: 8	Had this problem with an off brand 1953 with drums at all 4 corners. You need to make sure that the shoes and drums are clean of all contaminents (brake fluid, grease, etc.). If they are clean, then you need to adjust the star wheel so that wheels lock up in appropriate order. Usually, the front wheels are adjusted tighter than the rears. Mick 1965 C-10 LWB, Fleet __________________ Mick 65 C-10, LWB, Fleet Big Window, A/C

02-21-2001, 12:34 AM	#4
1965 C-10 Registered User Join Date: Feb 2001 Location: Vacaville, Ca U.S.A. Posts: 52	Yes the brakes are all clean, no brake fluid or gear oil, and I have the star wheels adjusted so the drums will turn with a small amount of effort, also I have been told since it is a shortbed fleetside, that there is not enough weight in the back of the truck, but I had a small block chevy engine complete riding just in front of the tailgate, and it still did it. ------------------ __________________ 1965 Chevy C-10 shortbed fleetside, 327,th350,3.73 to 1

06-06-2001, 08:38 PM	#6
c-10 racer Your long lost cousin Join Date: Dec 2000 Location: Cocoa, Florida Posts: 666	do those trucks have a metering (hold-off) valve. i'd look into that... it is supposed to hold the brake pressure from getting to the rear wheels until the fronts have build up good pressure... most 4 wheel drum vehicles have one __________________ 93 K1500 Ext. Cab

06-04-2001, 03:40 PM	#5
1972K10 Registered User Join Date: Feb 2001 Location: North Plains, OR, US Posts: 30	Look at the backing plates very carefully where the shoes rub against it. I had the same problem on my 1972 K10 and there were grooves worn into the backing plate where the shoes rub. I filled them up with weld and very carefully ground them back down smooth. Problem was gone. I had previous to this tryed new proportioning valve and bleeding several times to no avail. Start looking for grooved backing plates. Shoes need a smooth surface to rub against to work properly.



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