My '91 cherokee's brakes work great when its dry out. But if its raining, the braking sucks. The pedal acts the same when its wet out, I just have to press the brake pedal a whole lot harder and sooner to stop. And it takes much longer to stop when its wet outside. I can feel a big difference in stopping power when its been raining and the brakes are wet. Its starting to worry me!
Does that make sense?
The brake pads and shoes still have meet on them. Theyre not new but they look in okay shape.
What could be causing this? Any thoughts? I have 32" x 11.50" BFG all terrains if that makes a difference. But I had another '91 XJ with 33's and stock brakes and never had this issue.

 

You might want to check them to see if they are glazed. I had the exact same problem on a Nissan truck that I had many years ago. If they are glazed just change them out and you should be fine.

 

"Meat."

It's normal for brakes to lose action when wet - the water is a lubricant, y'know. However, they shouldn't be getting wet just because it's raining, so I'd make sure that the rotor shield plates and such are still in place, on the inboard side - and that they're not bent. (They're there to keep water from splashing on the brakes, more than anything else. They also keep crud from hitting your rotors.)

And, check for glazing (as mentioned previously.) It's obvious enough when you look - if the brake pads look like glazed doughnuts, they're glazed. Break with 120-grit sandpaper on a block or power sander.

If the rotors are glazed (instead of a "polished metal" look they'll look a little hazy - "glazed doughnut" appearance, again, after the doughnuts have been sitting for an hour or so and start to look kinda hazy and whitish) it's better to have them turned to remove the surface glaze than it is to do it yourself. Tell the shop to knock about two thousandths off of the surface on both sides - as long as you don't have any grooves or gouges, that's all you'll need to strip the glaze. Reinstall. (Better to reuse the old rotors as long as you can - they're already heat-soaked and bedded, and more reliable.)

After sanding the pads, avoid panic stops for the first 200 miles or so. If you can, go out and do a run up to about 50-60mph, then do a slow and smooth stop on to the shoulder. Wait 2-3 minutes, then repeat. Do 3-4x, this will help rebed the pads.

 

x3 sounds like glazed pads or rotors, or maybe just way cheap pads and you're used to better ones?