'72 Suburban - brake proportioning - The 1947 - Present Chevrolet & GMC Truck Message Board Network

WayneE · 04-26-2010, 01:43 PM

Are the brakes on these trucks heavily biased towards the rear? My '72 locks the rears very easily in the wet.

The P/O installed this setup on the truck (sorry for the crappy cell pic):

Front brakes are all new and a quick check of the manual for the proportioning valve/dist block doesn't show any adjustment for front/rear proportioning.

There is adequate vacuum at the booster and the check valve is working properly.

The truck stops well in the dry, but it's a handful in the wet. Just wondering if that's the nature of the beast or if I should be checking for problems.

Thanks!

zac · 04-26-2010, 02:33 PM

I had the same problem with my '72 years ago. A quick stop on wet roads was terrifying. It had what appeared to be the original proportioning valve. I ended up replacing everything in the brake system except the booster. This is back when a replacement valve was a fraction of the cost it is today. I never noticed the problem again, and I drove the truck alot.

In a weird side note, I ended up using the old proportioning valve on a '74 Chevy 3/4 ton van, for reasons that I can't really remember or explain, and I never had a problem, although I'm not sure I drove that truck enough to tell.

I'd be interested to know if others have experienced this problem on wet roads. It might be worth a shot to put in a new replacement valve. Is the one in the pictures for your specific application? It doesn't look like the new one I bought. But it looks cooler.

WayneE · 04-26-2010, 02:58 PM

Thanks for the reply, zac. The previous owner installed the booster and prop valve, so I'm not sure if it's appropriate for my truck or not. I'll have to dig around the paperwork included with my truck when I bought it.

71meangreenc10 · 04-26-2010, 04:24 PM

Make sure the rear wheels are adjusted correctly, if the adjuster wheels are no good, it will lock up alot in the rain.

Smitty

WayneE · 04-28-2010, 01:22 PM

Thanks guys. I hit up a local small repair shop that's run by an older guy. He said the brakes were fine and I was just used to newer cars.

My Camaro is a pro-touring car with Baer brakes all around, so it stops more like a modern car (but without the abs).

CheyLadd · 05-04-2010, 10:15 PM

I drove a 71 sub for 10 years and never had the problem of back brakes locking; wet, dry or snow. I don't think it is normal. One of the major complaints of subs of most generations is that they don't use enough of the rear brakes and thus they tear through front pads and rotors very fast. I would think if it were normal, all the trucks would constantly be locking since there is way less weight in the back but has the exact same brake system.

No solution for you but that is my experience.

04-26-2010, 01:43 PM	#1
WayneE Registered User Join Date: Mar 2010 Location: Frederick, MD Posts: 123	'72 Suburban - brake proportioning Are the brakes on these trucks heavily biased towards the rear? My '72 locks the rears very easily in the wet. The P/O installed this setup on the truck (sorry for the crappy cell pic): Front brakes are all new and a quick check of the manual for the proportioning valve/dist block doesn't show any adjustment for front/rear proportioning. There is adequate vacuum at the booster and the check valve is working properly. The truck stops well in the dry, but it's a handful in the wet. Just wondering if that's the nature of the beast or if I should be checking for problems. Thanks! __________________ Wayne - '72 C10 Suburban

04-26-2010, 02:33 PM	#2
zac Registered User Join Date: Jul 2008 Location: louisville, ky Posts: 502	Re: '72 Suburban - brake proportioning I had the same problem with my '72 years ago. A quick stop on wet roads was terrifying. It had what appeared to be the original proportioning valve. I ended up replacing everything in the brake system except the booster. This is back when a replacement valve was a fraction of the cost it is today. I never noticed the problem again, and I drove the truck alot. In a weird side note, I ended up using the old proportioning valve on a '74 Chevy 3/4 ton van, for reasons that I can't really remember or explain, and I never had a problem, although I'm not sure I drove that truck enough to tell. I'd be interested to know if others have experienced this problem on wet roads. It might be worth a shot to put in a new replacement valve. Is the one in the pictures for your specific application? It doesn't look like the new one I bought. But it looks cooler.

04-26-2010, 02:58 PM	#3
WayneE Registered User Join Date: Mar 2010 Location: Frederick, MD Posts: 123	Re: '72 Suburban - brake proportioning Thanks for the reply, zac. The previous owner installed the booster and prop valve, so I'm not sure if it's appropriate for my truck or not. I'll have to dig around the paperwork included with my truck when I bought it. __________________ Wayne - '72 C10 Suburban

04-26-2010, 04:24 PM	#4
71meangreenc10 Its a Truck Thing...... Join Date: Dec 2004 Location: Sierra Vista, Arizona Posts: 3,159	Re: '72 Suburban - brake proportioning Make sure the rear wheels are adjusted correctly, if the adjuster wheels are no good, it will lock up alot in the rain. Smitty __________________ 71 C10 283/3SPD Full Resto 71 GMC 1500 Sierra Grande http://67-72chevytrucks.com/vboard/s...d.php?t=518599 70 C10 Suburban Former military GSA truck. 72 Chevy Blazer 4X4, Sloppy Jo, Mountain Climber. Wife says no more trucks. http://67-72chevytrucks.com/vboard/s...d.php?t=707378 72 GMC 1 Ton Motor Home, wife said no more trucks until she saw this one. Gen 3 6.0/4L80E 4.10 http://67-72chevytrucks.com/vboard/s...d.php?t=761110 68 GMC Suburban was 3/4 ton, now 1/2.Wife shook her head 71 C30 Wrecker 71 C20 Scott-Bilt As weird as it gets..BB Cheyenne AC Truck 68 GMC Long Stepside. They keep following me home 71 C20 Longhorn/Ole Yellor 69 C30 Former Motor Home, Flat Bed time

04-28-2010, 01:22 PM	#5
WayneE Registered User Join Date: Mar 2010 Location: Frederick, MD Posts: 123	Re: '72 Suburban - brake proportioning Thanks guys. I hit up a local small repair shop that's run by an older guy. He said the brakes were fine and I was just used to newer cars. My Camaro is a pro-touring car with Baer brakes all around, so it stops more like a modern car (but without the abs). __________________ Wayne - '72 C10 Suburban

05-04-2010, 10:15 PM	#6
CheyLadd Registered User Join Date: Oct 2006 Location: Glendora, CA Posts: 85	Re: '72 Suburban - brake proportioning I drove a 71 sub for 10 years and never had the problem of back brakes locking; wet, dry or snow. I don't think it is normal. One of the major complaints of subs of most generations is that they don't use enough of the rear brakes and thus they tear through front pads and rotors very fast. I would think if it were normal, all the trucks would constantly be locking since there is way less weight in the back but has the exact same brake system. No solution for you but that is my experience.



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