An Unholy Union V: DRZ forks on an Airhead

Discussion in 'Airheads' started by Ras Thurlo, Jun 28, 2014.

  1. bleaknessengine

    bleaknessengine Been here awhile Supporter

    Joined:
    Mar 29, 2009
    Oddometer:
    211
    Location:
    Portland, OR
    i got them from swt, i think they are remakes of a magura bar. they came with 22mm fat bar adaptor/risers.
  2. antoinemo

    antoinemo Adventurer

    Joined:
    Jul 10, 2019
    Oddometer:
    39
    Location:
    NYC
    Hello unholy inmates! Has anyone been successful in fixing pads rubbing on the disc? I run an F650GS brake with Prutser's calipers and his Motomaster disc, with a new set of EBC HH pads. On initial mounting I get it pretty nicely setup with only a slight noise but the front wheel spins freely, however after flushing the brake system and pumping the brakes the pads rub quite a bit and the disc gets fairly hot. I can then spread the brake pads and remove a lot of the friction, but another pump of the lever and I'm back to a lot of rubbing and I feel like the pistons don't get back into the caliper enough. I changed the piston seals but that hasn't really helped. Could I have messed that up? Or should I take a look at my master cylinder maybe? I'm still running the stock MC. Any help appreciated!
  3. Motopsychoman

    Motopsychoman Not a total poseur Supporter

    Joined:
    Jun 2, 2013
    Oddometer:
    8,108
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    Oaklandish
    Stock 12mm MC?
    Prutser's calipers? You mean his caliper hanger with the F650 Brembo caliper?

    I have the Brembo 30-32 calipers on both my bikes and neither binds. Some things to check:
    1. Have you verified that the caliper is aligned correctly over the rotor?
    2. Does the caliper slide on the slide pins freely? With the wheel off, you should be able to push the caliper in and out with little effort.
    3. When you push the pistons back into the caliper, do they go smoothly or take a lot of force?
    4. Does the rotor move on the floater pins with a small bit of effort?
    The slight wobbling of the floating rotor is supposed to push the pistons back into the caliper very slightly so the wheel will turn freely. Any misalignment or binding can interfere by putting uneven pressure on the pistons or the slide pins. There is still a small amount of drag but it should be minimal.

    If it takes a tremendous amount of force to push the pistons back into the caliper, it is possible the seals are bad, the pistons/caliper are scored or the bleed hole in the MC is plugged not letting the fluid return to the reservoir.

    Just some thoughts.
    Scott in Missouri likes this.
  4. antoinemo

    antoinemo Adventurer

    Joined:
    Jul 10, 2019
    Oddometer:
    39
    Location:
    NYC
    Thanks Marty!
    You’re right, I meant to say Prutser caliper brackets, and I do run the stock 12mm MC. Brake pressure is plenty but indeed maybe there’s a problem with the fluid returning into the reservoir.

    1/ Alignment seems to be good. I’ve played with the bolts a few times and I’m not getting a lot of improvement. The pads seem to be rubbing evenly on the disc, and on initial mounting there is only a very slight noise. It’s only after the first application of brake pressure that things get worse.
    2/ Calipers slide well. I’ve polished the slide pins a bit and played with various amounts of grease and they seem to be moving ok.
    3/ They do take quite a bit of force. I’m not sure what to expect there once the system is fully setup? To me that seems to be the problem, when looking at the pads the pistons are definitely not at their most backed up position. I’m running the stock 12mm MC, I’ll take a look inside as a next step.
    4/ I’m not sure what you mean there. Are you asking if I can move the caliper back and forth on the rotor when looking at it from the side? If that’s it I can’t as the pads are rubbing pretty much on both sides.

    Thank you!
  5. Motopsychoman

    Motopsychoman Not a total poseur Supporter

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    On 3, the pistons should take some force to retract but not so much that tools are needed. I can normally push in the pistons using both thumbs against the pad, but it does take force.

    On 4, isn't your Motomaster rotor a full-floater? It should look just like this
    [​IMG]
    The big round pins with the holes are the floater pins. You should be able to wiggle the outer ring of the rotor just a bit (it will take a bit of force). The idea is that that small amount of wobble while rolling should push the pads away from the rotor when you are not braking (that won't happen when spinning the wheel by hand). It also allows the braking surface to expand and contract independent of the center, reducing the likelihood of warping. They way to test if the pads are being pushed back would be to ride the bike around the block, applying the front brake and then returning home using only the rear brake. The wheel should then spin pretty easily.
    I have an eBay Chinesium rotor currently on my G/S and it wiggles pretty easily. So did my prior EBC rotor. Some of the OEM full-floater rotors on my old Suzukis took a fail amount to make them move.
  6. Scott in Missouri

    Scott in Missouri Lake of the Ozarks, MO

    Joined:
    Feb 4, 2008
    Oddometer:
    475
    Location:
    Missouri
    Very nice reply. I'm always glad to see well thought out responses to help folks out.
    Restores my faith in the internet.
    The Patagonia Kid likes this.
  7. antoinemo

    antoinemo Adventurer

    Joined:
    Jul 10, 2019
    Oddometer:
    39
    Location:
    NYC
    Indeed- thank you Marty! You be been incredibly helpful all along!

    I took a look at the MC and it was leaking a bit, but that was hidden by my hand guards. Got the rebuild kit, cleaned everything thoroughly, pushed back on the pistons which got back in without too much resistance, put it all back together, and it feels quite a bit better. Still a bit of rubbing but on a short ride with as little front brake as possible the front disc only gets warm to the touch which wasn’t the case so it seems like the pistons are retracting without as much resistance as they used too. I’ll let the brakes bed for a couple hundred miles and monitor the situation.

    Indeed- I do have the floating disc. I can’t get it to move more than a hair though.

    So here goes, back on the road!

    C844BA4C-1F1E-46BB-8762-9E8C8F5D02BB.jpeg