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Converting to cable actuated rear drum brake, need input.

Discussion in 'The Garage' started by arcticXS, Mar 27, 2020.

  1. arcticXS

    arcticXS XS650 Guru Top Contributor

    As I totally prefer moderate rearset pegs, instead of the (too far forward) stock peg position, I am now considering converting the rear drum brake on both my XS650D and my RD350A to cable actuation, instead of the heavy and clunky stock brake shaft/arm/stay, plus the required linkage between rearset pedal and the splined shaft.

    DCC, and some other vendors are selling some setups, and on those, the cable ends up in a fairly severe S shape. Basically pointing aft, then down, then aft, like shown in the attached pic.
    On drum brake Yamaha roadracers, like the TR3, rs=w_600,h_600.jpeg Yamaha-TR3-1972.jpg the cable went up in a smooth arc, then down.

    I am thinking about having the cable point down at the pedal end, then arcing back towards the brake drum. Just making a pedal that is more or less straight, instead of L-shaped. That way, I can have the stopper for the cable sleeve on/attached to the static brake stay, which is the most convenient.
    I believe there are two main objectives here, minimizing cable friction, and minimizing any feedback of suspension movement into the brake. Feel free to provide suggestions, constructive criticism, and ridicule:)
     
    gggGary likes this.
  2. kevski

    kevski XS650 Addict

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    Another reason for the upward curve in the cables is they are not a water trap, which is what they become if you curve them downwards.
     
    gggGary and Paul Sutton like this.
  3. arcticXS

    arcticXS XS650 Guru Top Contributor

    Yes, I didn't think of that. I guess a rubber gaiter at the highest end will help a bit with that?
     
  4. kevski

    kevski XS650 Addict

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    On your first pic the curves are to tight and may hinder the braking, the mount at the rear of set up needs to be on the drum thereby straightening out the bend, you need to minimize the bends hence why in the second pic the cable takes the upward route allowing the cable to take a far gentler curve, you cannot do that by going under as the cable then becomes a snag hazard, it's about finding optimum curve and length
     
    arcticXS likes this.
  5. gggGary

    gggGary Stop that! XS650.com Supporter Top Contributor

    I agree I've seen way too many convoluted linkages. There is no reason a pedal/bell crank that PULLS one rod connected directly to the drum brake arm can't be designed and used. Hint the arm can be flipped so it points up rather than down. Check that you have a late model cam inside the drum that works in either direction.
     
    GLJ likes this.
  6. fredintoon

    fredintoon Fred Hill, S'toon. Top Contributor

    Hi arctic,
    move the bike's rear end forward in time from the 1950s, switch to a rear disk brake.
     
    gggGary likes this.
  7. arcticXS

    arcticXS XS650 Guru Top Contributor

    The problem with a rod, is that the front end of the rod needs to be very close to swing arm pivot, in order to avoid suspension movement interfering badly with braking. This is not always easy to accomplish with rearset pegs.
     
    gggGary and GLJ like this.

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