Ok so It's time to ask for ideas. My front left brake (GL1500) is dragging slightly.
With the wheel off the ground I can spin it by hand and it will spin only 1 - 1 1/2 turns. If I remove the caliper the wheel spins freely, with only the right caliper attached. The back brake releases nicely and the rear wheel spins freely (by hand) also. So the other two brakes are fine.
I have flushed and bled twice, with speed bleeders installed. The braking action is excellent. Pedal firm.
I have removed the caliper and the pistons and they were spotless. I cleaned them with just a toothbrush and some brake clean, as well as the seals and bores,then hit with clean DOT4 and re installed. I have also removed the caliper bracket and cleaned and greased the slider pins. I have removed the pads and cleaned the pins and the spring clip. There are no leaks anywhere.
Wheel bearings are fine.
After all this work, no change.
As a last ditch effort I did a fork alignment top to bottom.
The pads are worn evenly. The disk is no warmer than the rear after ridden.
Q: Am I just being too anal, or is there something I'm missing.
Shouldn't that wheel spin about 3 or so revs like the rear does
when turned by hand? And as it does with only the front right caliper attached?
You say the frotn wheel rotates 3 times with the left caliper off and right in place . 1.5 times with both in place . Have you removed the right caliper to see about the rotation with only the left caliper in place ?
The left caliper , connected to the rear system is used frequently and therefore might not be as relaxed as the right caliper . Do you use the front brake often ? Try stopping with the front and rear brakes together so that both calipers are recently used . Then check how free the wheel rolls with both calipers inplace or either in place. I am suprised the rear wheel spins freely . Disc brakes do drag . The have no retacting mechanism other than the seal/dust boot . That wont move a piston far .
KB - I did not do a rebuild, and did not disturb the seals. Therefore was not able to clean the grooves that the seals sit in. I did a gentle cleaning of the seals and pistons with a toothbrush, some brake clean spray and then DOT4. Everything inside was very clean when I opened it up.
OWP - I did not check with left caliper mounted only.
I do use more front than back brake, old school style, as I have been accustomed to for the last 35 years. After this last service and bleed I noticed improved stopping power from the pedal, so I am trying to use the rear/left hard too see if that will help settle it in. Went for a 2 hr. ride and checked when I got home but so far no diff.
I do believe that the front left was not performing well previously, and perhaps is still stiff. As mentioned it's very strong now, and am able to get the front end to dive a bit with just the pedal. So hopefully things will free up as you mentioned.
The only thing that helps the pads to fall away is the slight lateral movement of the caliper on the sliders. And mine are clean and greased. As you said the pistons barely retract. You made me think that if both calipers have an equal amount of drag then perhaps that resistance is simply doubled when both are mounted, and halved with only one on???
How well does your front wheel spin by hand when lifted off the ground?
Look close at the caliper pistons , with the pads removed and caliper in hand , AND hydraulic from bike attached .
When you put pressure to the pedal , you should see piston move forward , - and when you release pressure , YOU SHOULD SEE PISTON RETRACT A LITTLE ,(maybe 0,1 mm. ), - if it dosnt retract , it is time for rebuilding the caliper !
It is the special form on the seal and grove which retract the piston .