R80G/S upside down brake conversion

Discussion in 'Airheads' started by One Less Harley, Feb 6, 2010.

  1. One Less Harley

    One Less Harley OH.THAT'S GONNA HURT

    Joined:
    Nov 16, 2006
    Oddometer:
    5,457
    Location:
    Bowling Green, Ky
    I had noticed Nathan's (Boxerworks) G/S at the Georgia Mountain Rally last year and asked him about the upside down lever on his bike. He said it was easy to do, take a grinder and match the cam profile to the back side of the ears. So the seed was planted......

    Before picture stock setup

    [​IMG]

    Stock brake location

    [​IMG]



    Remove brake cam and make a cardboard tracing of the original
    [​IMG]

    Cut out cardboard and flip it over like so...
    [​IMG]

    Spray paint to get new profile
    [​IMG]

    Here's the profile.
    [​IMG]

    Start cutting w/ and angle grinder and cutoff wheel. Here's the 1st cut. Hopefully before cutting I don't have to tell you to remove the two o-rings...do I??
    [​IMG]

    ...And more. Proceed slowly and hold the grinder flat.
    [​IMG]

    Keep grinding till it looks something like this, this still needs a little work
    [​IMG]

    I was probably paranoid about weakening the cam as there wasn't as much material on the back side. See drawing.
    [​IMG]


    So I added metal w/ the MIG welder then smoothed down the welds.
    [​IMG]

    [​IMG]


    I then smoothed out the cam where the brakes will sit with a 120 grit sanding pad on a pneumatic angle grinder
    [​IMG]


    Then inserted the cam in the final drive, you will have to flip the brake shoes over and relocate the springs to the opposite side.

    I did notice that the springs may touch the OUTER edge of the FD seal. If this was on the inside edge I would be concerned. The reason for this is that the back bone of the brake shoes favors one side. A little hard for me to put into words but you'll see what I mean.
    [​IMG]


    Put the wheel on, not necessary to bolt it in place, you will have to adjust the brake arm to get it in the correct location. You'll have to fiddle with the arm to position it correctly. Bolt the wheel on then adjust the brakes. Ride the bike a bit to make sure the arm doesn't need to be moved. Once you get it in the right location mark the lever location on the cam with a center puinch.
    [​IMG]
    [​IMG]

    #1
  2. BubbaZanetti

    BubbaZanetti for a corrector life

    Joined:
    Jun 8, 2005
    Oddometer:
    13,160
    Location:
    Almaty, Kazakhstan
    it would have been easier to just flip the transmission upside down.:deal :lol3
    #2
  3. One Less Harley

    One Less Harley OH.THAT'S GONNA HURT

    Joined:
    Nov 16, 2006
    Oddometer:
    5,457
    Location:
    Bowling Green, Ky
    I really wasn't hard to do, just tinkering a bit.

    Flipping the tranny....Now there's a thought...... Humm... with an upside down tranny maybe the reverse light would be easier to replace, hey it wouldn't leak either!!!
    #3
  4. One Less Harley

    One Less Harley OH.THAT'S GONNA HURT

    Joined:
    Nov 16, 2006
    Oddometer:
    5,457
    Location:
    Bowling Green, Ky
    I've ridden the bike with the upside down lever, what I don't like about it.

    The brake gets tighter when pulled off the center stand and weight put on the rear wheel.

    also when ridding and putting pressure on the brake pedal, the brakes feel like they are out of round. I'm not sure why this is happening, maybe the cam shape isn't quite right? To me it feels as if the brake shoes are ridding up and down the cam.

    A third problem- even though I tried to mimic the profile of the cam, it is not shaped quite right. The off shape keeps the brake from engaging solidly.

    So, my conclusion is to remove the cam and return the lever to the stock location.
    #4
  5. BMW Fanatic

    BMW Fanatic n00b

    Joined:
    Jan 20, 2013
    Oddometer:
    6
    I also wanted to do this. Please put a couple of pics back on so I can see. How did you route the "pull rod" past the shock ? Or did you use a cable ? If you just ground 2 "mirror image" cams onto the back of the existing cams, did you weld up the original cam faces for strength ?
    #5
  6. One Less Harley

    One Less Harley OH.THAT'S GONNA HURT

    Joined:
    Nov 16, 2006
    Oddometer:
    5,457
    Location:
    Bowling Green, Ky
    sorry no longer have the picts. I was unhappy with pulsing while braking and went back to the original setup.

    I traced a pattern of the cam and and made a template then flipped the template over on the cam and cut the cam to the new profile. Hope this explains it well enough.
    #6
  7. Airhead Wrangler

    Airhead Wrangler Long timer

    Joined:
    Mar 4, 2008
    Oddometer:
    6,839
    Location:
    Back in Seattle, FINALLY
    It seems that later brake cams are usable for this without any modification, although I've never tried it. The later ones are just flat.

    This:
    [​IMG]

    ...instead of this:
    [​IMG]
    #7
  8. Jim K in PA

    Jim K in PA Long timer

    Joined:
    Mar 15, 2011
    Oddometer:
    2,185
    Location:
    Pocono Mountains, PA
    Hmmm - I wonder though if you would get proper leverage on the early style shoes with that later cam. I think the profile of the casting on the end of the shoe changed along with the cam profile. If you use the later cam, you probably have to use the later shoes as well. But, it may make for an easier conversion.

    I would like to do this lever flip as well on my '79. I have a spare early cam and rod, and was thinking about pressing off the cam and flipping it, rather than re-grinding the profile.
    #8
  9. Beemerguru

    Beemerguru Beemerguru...G/S guy

    Joined:
    Nov 7, 2006
    Oddometer:
    1,205
    Location:
    Redwood City, CA
    I've built 3 of them...but did it a little differently..I cut the cam off, reversed it and had it rewelded back together...

    Not me but a local machine shop that does all my crazy welding request.

    Never had an issue with pulsing and with proper adjustment and good shoes, no issues with binding
    #9
  10. One Less Harley

    One Less Harley OH.THAT'S GONNA HURT

    Joined:
    Nov 16, 2006
    Oddometer:
    5,457
    Location:
    Bowling Green, Ky
    If I remember right I had to swap the shoes around too..for some reason???

    I may have to look into doing it that way...
    #10
  11. greentreephrog

    greentreephrog Been here awhile

    Joined:
    Aug 29, 2012
    Oddometer:
    118
    Location:
    Laguna, Philippines
    As a matter of interest, are these us conversions being carried out because of some problem being experienced (perhaps in certain conditions), or is it more a matter of it just looks to be a logical modification to improve clearance?
    #11
  12. Box'a'bits

    Box'a'bits In need of repair

    Joined:
    Sep 26, 2008
    Oddometer:
    3,169
    Location:
    Wellington, New Zealand
    Looks, & also ground clearance. However most that do this wouldn't ever suffer issues - so it's mostly for looks. :D
    #12
  13. Jim K in PA

    Jim K in PA Long timer

    Joined:
    Mar 15, 2011
    Oddometer:
    2,185
    Location:
    Pocono Mountains, PA
    What Box'a said . . . :D

    Personally, I am doing to to get the cast brake arm up out of harms way. I have laid mine down in some rocks, and if a "simple" relocation can save my bacon when I am on the TAT, I am all for it.

    [​IMG]
    #13
  14. hardwaregrrl

    hardwaregrrl ignore list

    Joined:
    Jan 26, 2006
    Oddometer:
    8,184
    Location:
    Atlanta
    The only problem Ive ever had from crashing HARD on the right side was a bent rod......I swapped a cable for the rod and have had no problems since. Unitl I actually brake the arm, I don't see a reason to flip.
    #14
  15. Dmaster

    Dmaster Been here awhile

    Joined:
    Apr 3, 2012
    Oddometer:
    265
    Location:
    Netherlands.
    I only banged off the adjustment nut once, its a bit bend now but I don't care.
    Carry a spare one and a nut is way more easy (I don't even have one lol), and if you want to use the original suitcases you can't flip it up. It wil bang into it. (well at least if I flip mine up)
    [​IMG]
    #15
  16. Jim K in PA

    Jim K in PA Long timer

    Joined:
    Mar 15, 2011
    Oddometer:
    2,185
    Location:
    Pocono Mountains, PA
    Jenna/Dmaster - I certainly defer to your much greater experience. I have limited experience off road, but the few times I have played in rocky trails, I was concerned about a "lucky" hit on that cast arm. If it bends as Dmaster suggests, then it is far more ductile than I expected. That certainly reduces the likelihood of actually breaking it off.

    But if it can be broken, I suspect I will be the one posting up pictures of it! :rofl
    #16
  17. hardwaregrrl

    hardwaregrrl ignore list

    Joined:
    Jan 26, 2006
    Oddometer:
    8,184
    Location:
    Atlanta
    Well, I'm certainly not one to talk you out of it....but from what I've heard and the bike I rode with a flipped lever, I don't like the pulsing. Just seems like too much time, and the annoyance of an underperforming rear brake, and the slight chance of you busting the arm......=not worth it. I'll let you know when I break mine.:lol3 Then I'll flip!
    #17
  18. Pokie

    Pokie Just plain Pokie.

    Joined:
    Apr 4, 2013
    Oddometer:
    2,071
    Location:
    Fort Collins, CO
    I've turned mine over and re-formed the cam, haven't tried it yet, the bike needs a lot more work. I've jamed up and badly bent the actuator arm a couple of time now and would like to keep it tucked away out of harms way. I still have one of the bent arms that I'm going to use (upside down), seems like it is bent just the right amount to allow the rod to clear the shock, we will have to see to just wait and see.
    #18
  19. Jim K in PA

    Jim K in PA Long timer

    Joined:
    Mar 15, 2011
    Oddometer:
    2,185
    Location:
    Pocono Mountains, PA
    Hey Poke - any pitchas of da carnage? :wink:
    #19
  20. Jim K in PA

    Jim K in PA Long timer

    Joined:
    Mar 15, 2011
    Oddometer:
    2,185
    Location:
    Pocono Mountains, PA
    It's a deal. :deal :D

    Notwithstanding the potential interference with the Krauser panniers (thanks for the heads up on that Dmaster), if the cam is swapped on the shaft, or it is ground so that the obverse profile is 100% parallel with the shoe actuating surface, there should be no difference in feel, braking force, etc. when the arm is pulled from above the axle as opposed to below the axle. I suspect the bike you tried out had a cam that was ground inaccurately, and the shoes were being point loaded at the cam, rather than squarely spread. Just a theory.

    Also, the angle of the arm relative to the rod also makes a big difference in braking force. The rod should be perpendicular to the arm when fully actuated. That produces the most leverage. When flipping the arm on the splined shaft it can be tempting to locate it in a manner that provides the most clearance, but that may not provide the best braking. My rear drum brake will lock up my rear tire at will on any surface, so I have no complaints about it as is.

    It is a "simple" modification that has lots of potential ways to get it wrong, so leaving things as-is might be the best bet.
    #20