Front brakes dragging

[Skier]

I fear I may have caused myself another headache. While I had the front wheel off my Kat for my forks rebuild, I squeezed the brake lever for whatever random reason. This cause the calipers to push the brake pads together. They didn't go all the way together but I had to push them back into the calipers to fit the rotors back inside them. Now, I have the same problem before I rebuilt my rotors: the pads aren't touching on one side and are pressing against the rotor on the other.

This means I cannot spin the front wheel freely when it's off the ground. I don't think this is normal. I can spin the wheel for a little bit but the brakes do cause it to stop faster than my '86 Radian's front brakes do. Would bleeding the system help this? I doubt it, but it's the only thing I can think of. I just don't want to have to go back into those calipers again.

[The CyberPoet]

OK, the rotors should be self-centering on the rotor (and the hubs self-centering the rotor to the pads). It sounds like you have two or possibly three problems working together.

Step 1: Remove the calipers from the rotors. Loosen the bolts to the wheel (axel bolt, axel pincher bolts) without removing them all the way. Compress & release the front suspension about 6 times (this should self-center the front wheel in the forks). Now retighten the axel bolt and pincher bolts.

Step 2: Caliper piston inspection. Usually when the calipers are pressing unevenly on your year (where both sides of the front caliper have pistons), it's because one or more of the caliper pistons is frozen in it's travel due to either being lopsided in it's travel, or more commonly due to dirt (brake dust) build-up on the caliper piston surface. Eyeballs and maybe a measuring device -- are the pistons extending the same distance on both sides? If not, it's time for a caliper rebuild, which in plain English means disassembly, cleaning the pistons (scotchbrite & brake cleaner) and replacing the seals, or replacing the seals and pistons. Doing a search here at KR will net you the full process of how to do a caliper rebuild.
If the caliper pistons are all moving the same distance out from the caliper body, then the problem lies elsewhere, such as a bad wheel mounting (which we corrected in step 1), or an off-center or warped rotor (which means replacment). Spinning the wheel with the calipers off should let you eyeball the rotors to easily see if they are seriously warped. MC rotors rarely warp if they aren't below minimum thickness for replacement -- unless you dropped the bike at some point. If either rotor is warped, replace it.
If none of this was it (caliper pistons working right, rotor not warped, wheel centered in the forks correctly), then you need to look to see if the wheel isn't true, the axel bolt is bent, or the bearings are bad. With a bike that old, bad bearings isn't uncommon -- and fortunately, not all that expensive either (compared to rotors, anyway).

Good Luck!

Cheers,
=-= The CyberPoet

[Skier]

OK, the rotors should be self-centering on the rotor (and the hubs self-centering the rotor to the pads). It sounds like you have two or possibly three problems working together.

Step 1: Remove the calipers from the rotors. Loosen the bolts to the wheel (axel bolt, axel pincher bolts) without removing them all the way. Compress & release the front suspension about 6 times (this should self-center the front wheel in the forks). Now retighten the axel bolt and pincher bolts.

Step 2: Caliper piston inspection. Usually when the calipers are pressing unevenly on your year (where both sides of the front caliper have pistons), it's because one or more of the caliper pistons is frozen in it's travel due to either being lopsided in it's travel, or more commonly due to dirt (brake dust) build-up on the caliper piston surface. Eyeballs and maybe a measuring device -- are the pistons extending the same distance on both sides? If not, it's time for a caliper rebuild, which in plain English means disassembly, cleaning the pistons (scotchbrite & brake cleaner) and replacing the seals, or replacing the seals and pistons. Doing a search here at KR will net you the full process of how to do a caliper rebuild.
If the caliper pistons are all moving the same distance out from the caliper body, then the problem lies elsewhere, such as a bad wheel mounting (which we corrected in step 1), or an off-center or warped rotor (which means replacment). Spinning the wheel with the calipers off should let you eyeball the rotors to easily see if they are seriously warped. MC rotors rarely warp if they aren't below minimum thickness for replacement -- unless you dropped the bike at some point. If either rotor is warped, replace it.
If none of this was it (caliper pistons working right, rotor not warped, wheel centered in the forks correctly), then you need to look to see if the wheel isn't true, the axel bolt is bent, or the bearings are bad. With a bike that old, bad bearings isn't uncommon -- and fortunately, not all that expensive either (compared to rotors, anyway).

Good Luck!

Cheers,
=-= The CyberPoet

Perfect, thank you. I have already torn into the calipers and given them a full cleaning and rebuild with lots of those expensive little rubber parts, so I will check out the things you have mentioned.

[Skier]

After pulling and looking at the calipers, the pistons are not in there lopsided or anything. I set the front wheel to center as perscribed and put the rotors back on. Now there is only one pad that touches the rotor, but it's just barely touching it. I think it should be just fine, it's certainly not evident the brakes are on when pushing the bike around my garage.

[The CyberPoet]

After pulling and looking at the calipers, the pistons are not in there lopsided or anything. I set the front wheel to center as perscribed and put the rotors back on. Now there is only one pad that touches the rotor, but it's just barely touching it. I think it should be just fine, it's certainly not evident the brakes are on when pushing the bike around my garage.

If you look closely at the rotor, you'll notice that's joined to the carrier hub by little circular mounts (floating carrier hubs). In theory, the rotor can move left-to-right & visa-versa on these hubs to self-center to the pads, as long as the location the pads close down on are within the width of the space.
In theory, both pads should be barely kissing the rotor when the brake is off, and both should be pushing firmly against it when the brakes are on. To explain that in a little more detail:
With the same pressure being pushed onto the caliper pistons from the front master cylidner, both pads should come out and push against the rotors. When the pressure is released, the pads will stay there, but without any pressure against them to hold them to the rotor (there's no spring to cause them to retract). This is by design, since keeping the pads grazing the rotor lightly keeps both the temps for the brake friction system where it should be and continuously wipes away water or other contaminants that might otherwise interfere.
There is one other possible source of issues that I didn't cover, and that's the pin system the pads slide on; if this pins have a lot of build-up or any notching, the pad may not want to transit forward/backwards across that (more pressure being needed on one side to effect movement than on the other). Examining/cleaning these pins and possibly even lightly coating them with a very (VERY) thin layer of a high temp brake grease & rotating them can help in such cases.

The other thing you'll want to look at is the pads themselves: are the pads worn evenly, or are they possibly worn at an angle (where the front or rear edge is worn more heavily than the opposing edge)? If so, that indicates a past or present caliper piston travel issue.

Cheers,
=-= The CyberPoet