I recently purchased a 1998 Mazda Protege from a neighbor who told me it had braking problems. Upon test driving the car, I notices a severe pulsing from the brake pedal when braking. I immediately assumed that the brake disks were worn unevenly or warped.
However, when I went to inspect the disks, I noticed one of the front wheels was missing a lug nut. There are 4 per wheel. Is it possible that this missing lug could be causing the judder during braking? Also, if it is an issue with the brakes, is there a way to tell if the problem is being caused by a front disk, or a rear drum?
Is it possible that this missing lug could be causing the judder during braking?
I doubt if that is it, but it could be. Why not buy a new lug nut and find out. BTW If there are several lugs loose on the same wheel, then I would say it is likely that was the problem.
Yeah, i guess it wouldn’t be too hard to grab a new lug 
Assuming that;s not the issue, can brake drums cause this issue, or is it safe to assume it;s the front discs? Or could it be something else all together?
If the car shudders when you are braking, especially at a range of speed, say 55 mph to 40 mph, then you likely have a warped rotor. The last response by Joseph was right, replace the lug nut and make sure the other three lugs are tight. If they are tight, however, three lugs that are tight are enough to keep the rim stable while driving and braking, although it certainly isn’t worth the cost of a lug nut to see how far you can go with the current situation.
If you have a broken stud, or lug nut bolt, these either will be removable from the wheel itself (what’s left when you remove the rotor) or will be part of the rotor.
Rotors are cheap and easy to replace (for the most part).