Are you riding a bike without rear brakes because you can't find calipers that work for your frame/wheel combo? Do you have an older frame that you'd like to upgrade? If so, this is the instructable for you.
- TIG Welder
- Drill Press/Bits
- Wire Wheel
- Cantilever brake posts (new ones are available from Paragon Machine Works)
- Steel flatbar, 2ea, 1x1/4", 6" long
- Misc washers
- Silicon Bronze filler rod
Step 1: Starting Point
Here's my Frankenstein ride. It's a 1960s Gazelle frame, with 1980s Bianci mountain bike front fork and wheelset, and a random collection of other components. It's a fun ride, but I enjoy the extra stopping power and redundancy of rear brakes (it's a single speed, but not a fixie).
I thought about adding disc brakes, but I didn't want to spend the cash, or upgrade the wheels, which I'm quite happy with. I had a set of cantilever brake posts that I had cut off another bike that I had converted to disc brakes (I was glad I saved them!). Now I simply needed to attach them to the frame.
Before starting out, I took the cantilever arm that I planned to use, and put it alongside the rim so I could get the right position on the seat stay. Then, I marked this with a slight mark with a file. That way, when I stripped the paint off, I'd still be able to see the mark.
Step 2: Building the Jig
Using a couple pieces of scrap steel, I built this jig. I drilled ø5/16" (8mm) holes in the top plate, and a ø1/4" hole for the clamp, which is a simple piece of 1/4-20 threaded rod. The spacing of the studs can vary, but I used the 77mm center-to-center spacing.
After cleaning the paint of the brake studs, I clamped them to the fixture using 6mm bolts and a stack of washers.
Step 3: Attaching the Posts to the Frame
First, I stripped off the paint where I would be brazing the posts to the seat stays. I like to strip off several inches, as the smoke put off can be highly toxic.
I lined up the jig with the mark on the seat stay I had made while the rear wheel was still in place and eyeballed that the jig was square to the frame. It's not entirely critical that this is perfect, as the brakes are highly adjustable.
After a couple tacks on each post, I let the setup cool and then removed the jig.
Step 4: Test Fitting and Final Brazing
Next, I reinstalled the rear wheel and installed the brake components. The tacks are plenty strong to support them at this stage.
Everything lined up nicely, so I took everything apart again and finished brazing the posts. It's a good idea to do as much brazing as you can with the jig in place- as welding can cause things to move more than you expect.
Step 5: Final Assembly and Test Ride
Once everything cooled, I put everything back together, made the appropriate adjustments, and took it for a spin. Success! The extra stopping power, ability to stop with one hand (while getting keys out of my pocket), and redundancy are all welcome. Good luck!