What causes one brake to lock up?

[PHOENIX]

Ok this question is for a friend of mine who owns a F*rd (I think he would rather own a chevy truck, but he doesnt have money right now). But this question can be related to any disc brakes so I think its OK here.

Anyway he started hearing this rubbing sound coming from one of his front tires. He gets home and pulls the wheel off. He notices that he can spin one tire freely but not the other (both front). What do you think is causing this brake to lock up? My guess is something is wrong with the caliper.

I tried to call him right now to see if he got the caliper off and to see if the disc is still real stiff. When I talked to him last he was trying to get the caliper off, he was having hard time. Alot harder time then normal he said. If its not the brake caliper could it be another brake component? Im going to tell him to check the bearing. He just replaced the bearing not too long ago, so its probly not that. Now I wonder if he put enough grease on that bearing

Ohh well until I hear back from any comments are appreciated.

Thanks.

[BigRed]

Sounds like his caliper may be froze up. I have never had a bearing freeze up on me, but I've had them fall apart.

I can't see that it would be any other brake component, as it is only frozen on that one side.

[79BIG10]

I agree. Check the caliper for being frozen as well as the hose. I would replace the hose, caliper, pads, bearings, races, and seal to make sure and use lots of grease. I lubed mine up on teh spindle itself as well as the bearings packed full and then filled cap full as well. I think I used a whole tube on the front bearings alone.

[old Rusty C10]

try checking the rubber brake hose sometimes if its an older truck it cruds up and becomes blocked or the inside rots or something.
A worst case scenario is a blockage or kink in the metal line or the equalizer valve thats the order id go in assuming that there is no problem, with a pad or the caliper