Chevy & GMC Vans

i've noticed in the past few days that after the van has been sitting for a while, the brakes become very touchy. however as i drive/use my brakes, the better it becomes. is this a moisture issue?

thanks

My '90 'Stro's brakes were very grabby [the rear brakes mostly] especially when it was rainy. And mine went away too after driving a while.

The drums in my 93 are like that. very very very touchy when wet and as soon as they warm up they are normal. Like we are talking to touchy the tires were known to lock up at slight brake pressure when I stopped or slowed at the end of my driveway and then bam would be fine.

After sitting for several days, (especially in damp weather), the discs & drums will tend to get a light coating of rust on their friction surfaces. When you first apply the brakes, this surface rust gets 'scrubbed' off by the pads/shoes.... hence the 'grabby' feel of the brakes for the first few applications.

learn somethin' new everday!

that's awesome. this info is gonna save me haulin' the rear sneakers off to have a look inside the drums.

(it's cold outside)

Are there any other possible causes of this? Both my van and my Chevelle do this same thing. Grabby brakes at first, then after using the brakes 2-3 times they feel normal. But both vehicles exhibit this symptom after sitting only overnight, damp weather or not so I feel that rust may not be a likely cause.

Edit: Actually they don't even have to sit overnight. It happens when I start to drive home after work, as little as 9 hours.

6spd_monte wrote:Are there any other possible causes of this? Both my van and my Chevelle do this same thing. Grabby brakes at first, then after using the brakes 2-3 times they feel normal. But both vehicles exhibit this symptom after sitting only overnight, damp weather or not so I feel that rust may not be a likely cause.

Edit: Actually they don't even have to sit overnight. It happens when I start to drive home after work, as little as 9 hours.

High metallic content pads or ceramic pads?? Some of the new 'green' pads (environmentally friendly), are substandard in performance until the come up to temp. Some of the newer ceramic pads are touchy with cross-drilled/slotted rotors that have a bit higher nickel content as the coefficient of friction isn't there when temps are low. Nothing wrong, they just a bit picky at less than operational temps.

Usually a good 'bed-in' as the pads/rotors first seat into each other, cures most long-term problems.

I had an 1986 Safari cargo van for 10 years. At the same time my son had an 1988 Camaro. Both had disc brakes in the front and drums in the rear. Both had the grabbing problem when damp and cold or if it sat for a while. I spent a lot of time and money analyzing this problem. It was always the rears that would lock up the first 3 stops. I would park in a dirt parking lot. I would make the first three stops on the dirt and get out and see where the lockup took place. I replaced wheel cylinders, linings, cut drums, replaced fluid, replaced master cylinders, changed the brake adjustments to different settings and nothing cured it. I finally decided it was the design. The only correlation I noticed was the cheaper the lining the more it did it. I did some research and Raybestos linings seem to have the best reviews for GM vehicles. They offered standard, premiun and severe duty linings. I installed their premiun linings. It improved it a lot but I could never eliminate it. I now have an 1988 Astro. It came with good linings on the rear. It happens only once in while and only slightly. It is about 50% better than the 1986 Safari. It has to do with the interaction of the particular lining and the drum under different environmental conditions. It is inherent in the design.

That's what I like to hear, a design flaw, not a van problem!!

Thanks for the replies!!!!

As it seems many people are have encountered this, especially uncle-vinny's experience, it sounds to me like it's just the way things are with GM disc/drum systems.
To answer Jim in Indy's question, the Astro has Ac Delco pads in front, I don't remember what's on the rear. The Chevelle has pads from Kragen, and I haven't changed the shoes since I bought the car so I don't know what's installed.
I think I'll try Raybestos linings the next time I change the brakes, as uncle-vinny has had good results with them.

Thanks for the replies.

Whilst I agree with all that has been said here, IF you have a problem, it's probably bad rear axle seals. If there's any grease on the shoes, they grab like crazy till you burn it off. If I let my rides set for any length of time, I ride the brakes when 1st taking off to get mysef past the grabbing point.

hmmmmm, interesting.

are you suggesting that i take the rear tires off to investigate??

LOL