Brakes "Grab" in Wet Weather

Hi,
I have a 1979 Pontiac Bonneville. During (or shortly after) a heavy rain, when I drive my car and apply the brakes, the brakes behave as though I am "slamming" on the brakes. I know the
front wheels have disk brakes, but I don't know if the back wheels also have disk brakes.
What causes brakes to "grab" so easily in wet weather?
Thanks in advance, Brad
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When you say grab do you mean the nose dives or the front or rear's lock up? Need more info.
Brian
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Brad wrote:

Hi Brad...
Not an expert, not a mechanic - just know which pedal goes and which pedal stops me :)
However, I experienced this, and happily pass on what I learned if it's of any help.
Had exactly what you described; followed shortly after by the rear brakes locking up solidly if I as much as rested my foot on the brake pedal.
Turned out to be the rear brake cylinders leaking. Seems that brake fluid on the rotor and/or shoes does it.
Hope that helps...
Ken
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If it only happens once or twice when you first use them it is more or less normal, it is caused by both flash rust on the brakes and somewhat by the moisture causing flash rust on the shoes/pads. as long as it goes away after a couple of applications of the brakes don't worry about it. This condition can be really aggravated by the newer iron used in the rotors and drums, as well as using some of the newer versions of semi-metallic shoes/pads. Both my wifes 94 and my 95 van have the same reaction.
--
Steve Williams

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cheap pads... contaminated pads... moisture on the pads that turns to gas from friction with rotor.
the rear drums takes most of the braking force before the front do. rear end need adjusting, too much slop causes the grab effect when fronts aren't in top condition.
to fix: get higher quality pads, turn em rotors, and adjust rear brake drums.
-a|ex
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Based on the age of the vehicle I suspect it is possible that the rotor shields are completely rusted off. Mine were at less age. These shields protect the rotors and the pads somewhat. Without them water just sprays in there. It takes much longer to burn the water off with them missing.
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Al Bundy wrote:

Hi...
Now I'm confused a little (not unusual :)
It's always been my experience that getting brakes wet makes them virtually useless. (Drive through a puddle that's a little too deep).
Brake fluid is hydroscopic. Leak a little brake fluid so it gets on the pads, then add a little water and/or high humidity and you end up with a real real sticky substance. Lock the wheel in question very very easily.
Am I wrong?
Ken
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if you have a leak on the front end, you will know... spongy braking. low brake fluid light. hydrolic brakes will squirt that fluid quickly. brakes are separated into left and right zones. if one fails the other still works. so you will get uneven braking when one side is leaking.
i've used water to wash off dot4. but then again, i've switched to dot5.
-a|ex
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