I don't like _any_ difference between two wheels on the same "axle". Some get a bit worried when their front wheel doesn't spin cleanly, and they hear a dragging sound. That could be normal pad/rotor friction since the pad does not retract away from the rotor like shoes do when you have 'em on the rear (non-mustangs or older ones only of course).
If both front wheels feel the same, I would not worry. If one is hotter than the other, that's cause for investigation.
Again, there are two parts to this problem and one gets overlooked frequently...
(1) the pin is rusted because the small boot is cracked. Or the pin feels like it has tar on it because the old grease has solidified, absorbed dust/dirt/water or whatever. Clean the pin. Crocus cloth 9r very fine emory paper will make it as good as new. It needs to be smooth, but it doesn't have to be polished.
(2) the hole the pin goes in on the bracket is important as well. If the pin is clean, but the hole is full of crap or rusty, the problem will return soon or never go away. The easiest way to clean this is to go to Wal-mart and go to the sporting goods department. Buy one of the small round metal gun-cleaning brushes (38 caliber will work, although it will be a little tight). Use that with some good solvent and scrub those holes out until they are clean. Dry them out and insert the pins. They should slide in freely.
Once you have them clean, apply some good high-temp grease to the pin, slide it in and turn it a turn or two. Remove it, grease it again, and repeat until you are convinced that everything inside is coated with grease. Reassemble and the problem will be gone.
Only three things can cause dragging brakes, and one can be eliminated quickly.
1. pressurized system. Caused when another brake is dragging, boils the fluid which pressurizes other calipers and makes them appear to be bad. we had this happen on our left rear caliper, but we noticed the right front dragging since we more often work up there. We had lost a few 10ths in the 1/8 mile as well, and began to notice a general loss of power everywhere. This was the cause.
To eliminate this, just crack the bleeder valve on the one that you are checking. If fluid comes out, this is most likely your problem. Once you release that residual pressure, the wheel will probably spin normally. Now press the brake pedal again and check for number 2.
2. Caliper piston is sticking, almost always a result of rust caused by the dust boot cracking and letting water in. This can be repaired easily enough if the piston is not completely stuck. Remove it, and with the brake line still installed have someone _slowly_ press the brake pedal and push the piston(s) out. If you have dual-piston calipers, this can be a bit of a pain so if one moves and one stays put, use a big c-clamp, or block of wood to prevent the one that is moving from popping completely out. Now continue pressing the pedal and push the other one out. You can then pull them the rest of the way out and now all you need is to remove the rust/gunk in the caliper bores, and then clean up the pistons. I again use crocus cloth, but anything that is _very_ fine (steel wool for example) will work. Put that 400/800 grit emory cloth away. It will remove more metal than you think and you do not want a distorted bore or piston. Once it is cleaned up, clean the caliper out (now you disconnect the brake line but don't let the fluid drain out as air in the ABS is a bitch..) Clean everything up, install a new o-ring from the rebuild kit you did remember to buy, lube the piston with new brake fluid and it should go in smoothly with hand pressure. Once the o-ring and piston contact, it will get a bit tighter so you can use a c-clamp or brake caliper tool to seat it all the way. Re-install and bleed.
3. ALl that is left is the sliding floating caliper pins, which I explained how to clean up above.
There are some other very rare problems, such as a bent bracket which cocks everything slightly and can cause sticking. But almost every sticking brake I have ever worked on fit one of the three scenarios above...
Too many clean the pins and then stick them into a hole full of monkey-crap and wonder why their brakes still stick. Because monkey crap is sticky. So get it out of there.
