Jeep pulling under braking

I have a 98 XJ Sport. When I brake HARD the jeep seems to pull to the side rather aggressively. I havn't noticed it going to one side specifically and after it's first pull it straightens out for the rest of the brake. It only does it when I brake HARD but that's the time I need the most control. I noticed it the first time when someone pulled out in front of me. I braked HARD and the jeep pulled right and I almost hit the curb.

I have 99,000 miles on it now. I have 1" suspension spacers around. Rancho RSX shocks up front with Air shocks in the rear. I was given a set of poly bushings for the front so i'll be messing around with things and installing a new Rancho Stearing stabalizer.

Any ideas as to what could be causing this?

OUG

The first suspect is a bad rear brake adjuster. The adjusters tend to rust, come apart, or otherwise fail to work, and when that happens you'll get a strong initial pull that straightens out once all the brakes engage. You'll also exacerbate the tendency to lock up under light braking in the wet, a very common XJ complaint, tow hich many solutions have been suggested. The only one that's ever worked for me was to manually adjust the brakes.

There is a TSB for this problem. The fix (after eliminating any and all brake possibilities) is to shim one of the front wheels...I forget which one. Search around the internet for the TSB.

I forgot to mention above, the first check you should probably do, assuming it is not ABS equipped, is to take it somewhere with either a loose surface or to a parking lot, and hit the brakes hard enough to lock up. The starting point and length of the skidmarks can be very informative.

Although my experience suggests that a bad adjuster is the first suspect, there are other possibilities. A warped rotor or a loose front wheel bearing can cause one caliper to push out further than the other, resulting in delayed braking on the bad side and a pull to the good side. Hydraulic issues can also cause problems which can be a bear to track down. Deteriorated hoses can sometimes flake internally, causing erratic braking without any visible defect.

Thanks for the information guys. One of my rear tires does lock up on wet roads under light breaking. I've done a few things under the hood but, I've never done a rear brake job by myself. I just got my shop manual so i'm sure I'll have to see what it says. Is this something I should just try and keep tweeking till it works or should I take this somewhere and have it done?

I had the same problem with my "new" '96, scary even on an empty road. I'm not a big fan of rear brake work either. I pulled the rear drums to check wear and condition, all was well except one adjuster was way out of adjustment. Pulled, lubed, replaced the drum and readjusted the adjuster and all is well when doing the "empty road panic brake test". If the simple doesn't fix the problem, break out the manual and replace the brake fluid if it's been a few years.

You guys rock.

Thanks again.