'77 R100RS Front Caliper Removal Woes

Discussion in 'Airheads' started by shadeobrady, Jun 29, 2019.

  1. shadeobrady

    shadeobrady Adventurer

    Joined:
    Mar 30, 2016
    Oddometer:
    22
    Location:
    CA, USA
    Hey folks - sorry to blast you all again. I don't know why something as simple as a brake pad replacement is giving me so much trouble here...

    I've removed the cap screw and spring from the bottom of the left caliper (shown below).

    The last step in the Clymer Manual (before yanking off the caliper) says:
    "Thread an 8 mm x 1.25 x 50 mm bolt into the bearing pin. Withdraw the bearing pin from the brake caliper and fork slider."

    I'm completely stuck here - I tried threading up an 8mm bolt I had laying around and it's catching nothing up there. I can see a cam up there that adjusts the angle of the pads on the disc by screwing left and right (I believe).

    My understanding is there's a pin up in there that's the only thing left holding the caliper in place that's stopping me from pulling it off and accessing the pads.

    Am I totally missing something here? :confused

    IMG_2127.JPG IMG_2128.JPG IMG_2129.JPG
    #1
  2. bmwrench

    bmwrench Long timer

    Joined:
    Nov 10, 2006
    Oddometer:
    7,705
    You don't need to remove the pin to replace the brake pads. Retract the "live" pad by prying against the "dead" one until the piston is pushed all the way back. Remove the clip from the dead pad and remove the pad. Next, simply pull the live pad out.

    The pin is eccentric and simply pulls out of the fork slider. Sometimes, though, they are stuck, and need extra measures. There is an 8mm thread inside it.
    #2
    shadeobrady likes this.
  3. Big Bamboo

    Big Bamboo Aircooled & Sunbaked Supporter

    Joined:
    Sep 29, 2010
    Oddometer:
    16,344
    Location:
    Big Island of Hawaii
    You'll have to take the wheel off first... :D
    #3
    shadeobrady likes this.
  4. TwoShoes

    TwoShoes How Many Shoes?

    Joined:
    Aug 18, 2003
    Oddometer:
    484
    Location:
    Fredericton, New Brunswick, Canada
    If it's catching nothing, are you sure you're using a correct bolt? I usually just use one of the front axle pinch bolts, it's right there and removed (assuming you've taken the wheel off first :-))
    #4
    dmftoy1 likes this.
  5. Disston

    Disston ShadeTreeExpert

    Joined:
    Aug 31, 2009
    Oddometer:
    16,157
    Location:
    Silver Spring, Md
    I use the longer bolt holding the fender brace and then I have something to pull on. Sometimes I have even beaten on this bolt with a screwdriver and hammer to get the eccentric pin out.
    #5
  6. bmwrench

    bmwrench Long timer

    Joined:
    Nov 10, 2006
    Oddometer:
    7,705
    On the rare occasion that the pin resists extraction, I make up a puller with a bolt and spacer. Seems like the last time I had to do so, I used a socket.
    #6
    Big Bamboo and dmftoy1 like this.
  7. shadeobrady

    shadeobrady Adventurer

    Joined:
    Mar 30, 2016
    Oddometer:
    22
    Location:
    CA, USA
    Thanks folks! I'm a dummy - I was apparently using an M6 or M7 - double checked a larger size (M8) since I didn't have them labeled and it came out immediately!!

    Now that it's all back together, getting the angle correct has been interesting... that may just take trial and error I guess (which sucks since it's my freakin brakes).

    How exactly does that work? I could see sliding out the "dead" pad with the clip, but the "live" outside pad slides into a hole. You can actually get enough space in there to pull one out/put one in against the disc?
    #7
  8. Big Bamboo

    Big Bamboo Aircooled & Sunbaked Supporter

    Joined:
    Sep 29, 2010
    Oddometer:
    16,344
    Location:
    Big Island of Hawaii
    Not with the disc in the way. I've used my fingers to push the pad with the piston back into the caliper. Beware! If you have recently topped off the fluid reservoir, it WILL overflow out the top! I use a turkey baster to suck some out. It's a good time to renew the fluid anyway...
    #8
    shadeobrady likes this.
  9. nobbylon

    nobbylon Long timer

    Joined:
    Aug 13, 2012
    Oddometer:
    1,076
    When you have the pads adjusted so that they are biting parallel hold the brake on while you replace the spring and bottom cap.
    #9
    Kiwiabbo and shadeobrady like this.
  10. Disston

    Disston ShadeTreeExpert

    Joined:
    Aug 31, 2009
    Oddometer:
    16,157
    Location:
    Silver Spring, Md
    It's this thing about the pads biting parallel that gets me. The pads are parallel no mater what position they are in. They are cut parallel. Now I have to set them so they are parallel to the disk, I think.

    Last time I got a response from Bud he said something about the pads being closest to the inside edge of the disk? Is this the position the caliper is mostly forward also? It would be so easy if that was it.
    #10
  11. nobbylon

    nobbylon Long timer

    Joined:
    Aug 13, 2012
    Oddometer:
    1,076
    Look at the pads and disc and there will be one position that looks like the pad surface is parallel to the disc at contact with the disc when lever is pulled. Now pull the brake on so the pads are close to the disc and fine tune with the eccentric so that when you pull the brake lever you get 100% contact. Release the lever and spin the wheel and check again after you have pulled the lever again. Once you’re happy pull the brake on and refit spring and cap. I’ve set mine up like this for years and always had good brake power and feel. When set up correctly the caliper doesn’t move. Hope this helps.
    #11
    shadeobrady likes this.
  12. nobbylon

    nobbylon Long timer

    Joined:
    Aug 13, 2012
    Oddometer:
    1,076
    I’m sure that airhead brakes get a bad rep’ because of poor set up and pad choice. Well....on double disc anyway ;)
    #12
  13. shadeobrady

    shadeobrady Adventurer

    Joined:
    Mar 30, 2016
    Oddometer:
    22
    Location:
    CA, USA
    Yeah - I was incredibly confused when trying to get the eccentric lined up... never seen something like that as far as brakes are concerned.

    Thanks for your extended explanation above - very helpful!
    #13
  14. Disston

    Disston ShadeTreeExpert

    Joined:
    Aug 31, 2009
    Oddometer:
    16,157
    Location:
    Silver Spring, Md
    In the past I have not had this problem. It's only recently and I think it may be related to the rotors I have on the bike. For some reason I don't know why but that's what I have been thinking I may try messing with. So I have another front wheel from an R100S bike I took apart some years ago and gave a lot of the parts to away. I still have the front wheel. Very old tire tho. But if I can get the brakes working I'll put a new tire on it.
    #14