Originally Posted by
TiHabanero
... ... and just yesterday started modifying the brake mount. The drag brake is for a single person bike, not a tandem. Weight load will be significantly less than a tandem. Hoping a 160 rotor will do the job as it is as large as the frame will accept. Doing this more for winter fun project than for actual application on a touring rig, however if it works out as envisioned, then I will keep it on the bike.
As for the Suntour chain stay mounted brakes, they work exceptionally well, better than cantis or V-brakes. Coupled with the Can Creek EC5 brake levers they are remarkably easy to apply, as in power brakes in a car vs the old non-power brakes (first car had 4 wheel drums and they were a handful in panic stops). Love the modulation. I have the KoolStop salmon pads on them and will put these things up against any rim brake out there including hyro rim brakes. Yes, they are that good. Road use only, off road the position collects crud and makes them less effective.
I can understand experimenting with a bike as a hobby, and from your past comments I understand you have competence with fabricating things like racks and have mechanical skill. That said, I agree with Inanek, you can put a lot of torque on the stays and dropouts with a disc brake.
When people first started using disc brake mounts as the torque control lever for a Rohloff hub, I was surprised that the frames did not fail. But from that we have learned that frames with a disc brake mount are built to be strong enough to handle the torque from a Rohloff hub. I would assume that your disc brake can put a lot of torque on the dropout of a rim brake frame.
Do a google search for
images of broken frames and rohloff hubs and you will see lots of photos of rim brake frames that cracked from the torque that a Rohloff hub can put on a frame.
I pulled this image that shows a cracked frame with a Rohloff hub from the internet from using that search.
My 1960s vintage utility bike with drum brakes (rear hub is a Sturmey Archer 3 speed, with drum) is in storage behind some other stuff, but I managed to get a photo of the brake and torque arm to include here (the bike is hanging from the ceiling from the front wheel, thus forward on the bike is up in the photo):
You can see that the torque arm is attached to the chainstay so that the brake does not apply all torque to the dropout, some of that force is applied to the steel chainstay.
So, I suggest you do not try to do any panic stops with that disc brake modification you fabricated, especially down hill.