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K75 front brake rubbing

barooo

New member
I just finished my fork job and reassembled everything, and I noticed that my front brake is rubbing slightly. If I raise the wheel and spin it it can be spun, but it stops almost immediately. I re-loosened the axle and the 4 bolts on the forks and re-seated everything (compressed the forks 6-8 times), and I cleaned the pads and rotor. This seemed to help a little, but it could be my imagination.

Don't know if it was doing this before I removed the wheel for the fork job or not. I hadn't ever noticed it and I could tell something was a bit off when stopping/starting. After cleaning, etc. I no longer notice it riding but it still has a hint of friction when spinning the wheels.

So, 1. is there a trick to re-installing the front wheel or forks I am not aware of that could cause a caliper alignment issue? If not, am I possibly looking at a caliper rebuild or something? and 2. would just re-bedding everything (do some hard 60-5 stops then let everything cool down) maybe help, or perhaps new pads (although they'd be thicker and therefore probably worse, no?), which I was going to do this winter along with braided stainless lines and a flush. I notice no pulsing or noises when stopping so I don't suspect warped rotors, and prior to the disassembly had noticed nothing, either. The right rotor was warm (not glowing hot but uncomfortable), the left was cool, so it seems to be primarily the right.

This is an 87 K75T (disc front drum back), 40K miles. I believe it's the original rotors since I don't see antything in the history about rotors.

On the plus side I'm in love with the progressive springs already.
 
Because there is nothing in the brake system to pull the pads away from the rotor when you release the lever they will always slide across the surface ever-so-slightly. A bit of dirt or corrosion on the piston can keep it from retracting far enough to not create drag.

In your case, I'd pull the offending caliper and clean under the piston to caliper seal. Look for crud on the piston, you might need to remove it and use a bit of emery cloth to polish off the crusties. You might also need a new seal ,they don't last forever.
 
FYI, it seems fine now, cleaning the pads and actually riding it a bit seems to have knocked some sense into it. I still think new pads and some caliper inspection, and a fluid flush is in the near future for me, but it's no longer dragging. I'm trying to get together pads, spiegler lines, and time to do it.
 
FYI, it seems fine now, cleaning the pads and actually riding it a bit seems to have knocked some sense into it. I still think new pads and some caliper inspection, and a fluid flush is in the near future for me, but it's no longer dragging. I'm trying to get together pads, spiegler lines, and time to do it.

There is normally some drag on the front rotors from the brake pads although it should be minimal. If there is room in the brake fluid reservoir you can push the pistons back into the caliper and the fluid will push up into the reservoir. Otherwise the pistons would not normally return to the fully retracted position. You want to push the pistons all the way in when replacing the seals so that there is the least amount of air in the calipers when refilling and bleeding the system. But that is only when you split the calipers for a rebuild.

The way it has been explained to me the drag on the rotors keeps them warm and dry (or drier than they would otherwise be) which improves braking performance. Your brakes are least effective when cold and they warm up due to the slight drag.

If you pulled the front wheel without blocking the pads the pistons and pads could have moved out from their normal position and then when you reinstall the wheel the pads rub more than usual on the rotors. Once ridden things return to normal and the rubbing is minimized.

Try putting a soft spacer in the calipers next time you remove the wheel. That will prevent the pistons from moving out and restricting the space. Can make it easier to reinstall the wheel, too. Again there has to be someplace for the fluid to go so don't overfill your reservoir.

I use a piece of cardboard covered with duct tape for my spacer. It's not elegant but it works and it's easy to get it just the right thickness by layering the tape wrapped around it. If the pistons do move out (for example you forget the wheel is out and squeeze the brakes you can push them back in by gently using a large flat blade screwdriver to pry the pads apart. Be very gentle.

Ride safe,

-Gary
 
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