Tight Front Wheel

[jphan]

I replaced the right front brake line and bled the lines on my 1997 R1100RT(21000 Mi.). The brakes work great but the front wheel does not spin freely. The calipers seem to be dragging on the discs. Do the calipers need to be rebuilt? My BMW dealer says you cannot rebuild the calipers. You have to replace them for $400-500. Comments or suggestions please!!!

[BubbaZanetti]

how much drag are you experiencing???

all my bikes have had some level of drag from the brake pads, maybe you need to try pushing your pads back off the disc a little, careful, it may overflow the reservoir if you filled it up

[jphan]

If you push the wheel hard it may turn one revolution. I've had the calipers off a couple of times and have pushed the pistons back to their stops. When you pump the brake pads back out again they stay right on the discs.

[dbrick]

The same symptom might occur if one or both of the brake disks are not free to move laterally on their mounting buttons.

[jphan]

I don't understand. Could you explain further about the lateral movement of the brake pads dragging on the discs!

[dbrick]

I assume the disks on your RT are mounted in the same way as those on my RS: they "float" laterally, on little aluminum bobbins. While the flexibility in the brake caliper piston seals pull the pistons back just a bit after brake application, so the pads don't drag on the disks, they can't pull the pads back very far.

If the disks don't move laterally a little, then even though the pads retreat a little, they (the pads) will drag on the disk once each revolution. (This is the same symptom you'd see with fixed (not floating) disks, but the cause there is warped disks, not stuck bobbins.)

Grab the edge of the disk at a point opposite to the brake caliper. Can you wiggle the disk laterally? Rotate the wheel 180 degrees, and do it again. If you can wiggle the disk laterally at both orientations of the wheel, then the disk is floating correctly, and your problem is somewhere else. If at one (or both) of these orientations of the wheel you can't move the disk, then the disk mounting (the aluminum bobbins) need to be changed.

[boofer]

Disc brakes are supposed to have a slight constant contact between the pads and rotors. Run it ten or twenty miles at highway speeds, stop and touch a rotor. Should be warm, if you burn your finger ya got a problem.

No, the seals don't pull the pistons back in the calipers.

Tim