Are My Front Rotors Bad?

How does someone know? What am I to look at?

You have to look at the manual or a service bulletin. Go to Backyard Mechanic and click on the Nissan Factory Service Manuals online thread. There is a certain width that it cannot exceed and this has to be measured by calipers. The other way to tell is if they are warped. How many miles are on your truck, and did you buy it used or new??

I bought it used with either 18,000 or 28,000 miles on it (can't remember). It now has about 34,500 miles.

The limit on a 2002 is 26mm I really don't think that your rotors are already worn out at that mileage...but crazier things have happend. They could be warped also, a couple of members have had their rotors warp prematurely. You might just have to turn them (common thing). You have to turn rotors when you have some uneven break wear and it creates ridges. What makes you think that there is a problem?? Did you have any wheel/brake done recently?? Could be an over-torque or under-torque of a fastner.

Chato,
What is happening for you to suspect they are bad? As lincolnnellie mentions, there is a minimum thickness for the rotor, and there should also be a runout to ensure that the surface is flat.
If you are getting a pulsation through the brake pedal under braking then it is time to turn or replace the rotors. There are any number of reasons why this could happen. But 34k is pretty low to swap out the rotors. Please describe your symptoms...
Bogatyr

Well, I really don't know if they're bad or not. I'm going to be replacing my front brake pads tomorow (got a bad case of the squeeks), and I guess I'm pretty paranoid considering how brakes and rotors go together. I'm hoping I haven't waited too long to replace the pads, and I guess I'm wanting to be able to look while I the tires are pulled off, and be able to tell by looking if I've caused any damage to the rotors. I don't want to put new pads on and have bad rotors. Kind of defeats the purpose to me. I'd rather go in knowledgable you know? I've never had any tire or brake work done since I bought the truck about a year and a half or so ago. Matter of fact, I'm still wearing the same tires that appear to have come stock (crappy hydro-planing BFGs).

Chato,
Ah, I see now. If you're squeaking because your pads are down to the wear indicators, then chances are you've damaged them a bit. How bad is another question. If this has been going on for more than a few days, I'd certainly turn them. If there's a deep groove in the rotor, then you should replace them. Just note where the wear indicator is and feel in that position (usually on the back of the rotor...) for a groove. In an emergency (like if you can't get the rotors off) you could drive on the damaged rotors, but bear in mind that due to the width of the groove worn into them, you will lose a bit of braking effectiveness up front.
You're certainly correct that if you replace the pads, and the rotors are shot, you aren't helping much.
Heh, I know what you mean about those BFG Long Trails. When I got my truck, they were at the 35 pound max inflation...no wonder she was hydroplaning...I dropped that down a few pounds and it seems better now...
Bogatyr

Hey man, thanks for your helpful reply. I'll check for that groove. Is turning the rotors a difficult task to do? Any direction or instructions you can give or refer me to?

Usually turning your rotors only costs like 5.00 a piece at a local autoparts store. Unless you have the right equipment...you can't do it yourself. Take them to Autozone or Pepboys. It is good practice to turn your rotors every now and then when you change your brake pads. If you have any doubts at all as to whether they should be turned or not, then bring in to the store and they should be able to tell you if you need it or not. Come armed with knowledge though...know your minimum thickness before you go. I am going to e-mail you the service page on brakes...it has all the specs on it. Good luck.

Excellent, I can't thank you enough! HUGE help!

Problem is, pulling the rotors on an Xterra isn't exactly trivial. "Top hat" style rotors that slip over the studs just like the rear drums are a cinch, but the ones like ours that are bolted to the hub and require the whole wheel hub to come off are a bit of a hassle.

Brent

This is typical mounting on most cars. If your rotors are warped (ie: Brake Pedal pulsing and/or your ride is pulling to a direction when brakes are applied) it is better to buy new rotors for $35-45 each as the warp is "set" into the metal and will return quickly....WARPED ROTORS ARE TRASH and turning them will only temporarily remedy the problem. Grease the backs of the pads where they contact the caliper piston to avoid rattling. Alll rotors should be cross hatch sanded on a brake lathe prior to installing pads even if the rotors are new.