Home Built Rear Disc Brake Conversion

rick_p

100 W
Joined
Feb 16, 2021
Messages
260
Location
Los Angeles
The following demonstrates one way to covert an eBike rear wheel to a disc brake, but note that this bike was an eBike from the factory, so this method may or may not be applicable when converting a regular bike to an eBike.

The bike is an early Pedego Interceptor and the original rear wheel was a drum style brake. The frame is wider than most bikes to accommodate the drum brake.The bike was operational when I bought it (second hand) and would have been a death trap were it not for the front disc brake because the rear drum brake was awful.

The hub motor started sounding like coffee can full of nuts and bolts rolling down the street, and not much later it died. I might have considered fixing it but since I already hated the brake, I decided to buy a new wheel.

Here's a picture of the old wheel:
Drum-wheel.jpg
Here is a picture of the new wheel already mounted on the bike with washers added on both sides to center. the wheel in the frame. Note the two factory threaded holes intended to mount a fender:
Disk-wheel.jpg

To get started I needed to get a sense of alignment between the caliper and the frame, so I centered the pads in the caliper and clamped the caliper on the disk using a short piece of brake cable to squeeze the pads against the disc:

caliper.jpg

With that in place, using a piece of raw material (3/16 flat aluminum) I was able to determine where the bracket aligned with the frame, and in this case it (luckily) aligned with the outer torque washer being used as a spacer:

bracket-spacing.jpg

Next, I mocked up the bracket design, but this step is purely optional, it just helped me visualize the design of the bracket.

bracket-mockup.jpg

Using a piece of Foam Core as template material I tested my design with something easy to cut out that was approximately the correct thickness:

bracket-template.jpg

From the rear angle you can see that the template aligns nicely with the caliper bracket (on the left), and rests on top of the frame of the frame (on the right), which will act as a torque bracket when braking (prevent rotation):

bracket-template-alignment.jpg

Next step was to cut the actual bracket. Note that before cutting the real bracket I changed the design slightly from a slot to a hole with two flat sides. This will help prevent the axle from turning from motor torque, but I also moved the torque washer to the outside to double up on motor torque rotation prevention. Brake torque rotation of the bracket is handled by the combination of the bracket resting on top of the frame, and two bolts through the frame and into the bracket:

bracket-template-transfer.jpg

Test fit and final adjustments:

bracket-test-fit.jpg

Finished product. Note that I have put 500 miles on the bike since the conversion and have braked hard several times to test the strength of the bracket, bolts, and design:

bracket-final-fit.jpg

I hope this was helpful for your project :)
 
Finish it off nicely with an upgrade to hydraulic. I’ve seen them for under $50. I’m using some right now on a fatbike conversion, better than the cable pulling type.
 
Skaiwerd said:
Finish it off nicely with an upgrade to hydraulic. I’ve seen them for under $50. I’m using some right now on a fatbike conversion, better than the cable pulling type.

Good call!!
 
Skaiwerd said:
Finish it off nicely with an upgrade to hydraulic. I’ve seen them for under $50. I’m using some right now on a fatbike conversion, better than the cable pulling type.

Better at failing. Better at leaking their "cable" onto the pads and ruining them permanently. Better at resisting the user's attempts to maintain or repair them, or even just change the hose length to fit the bike.

If you prefer things to be disposable, then hydraulic bike brakes are for you.

If you'd rather have a bike that stops well all the time and is easy to work on, Avid BB7.
 
Chalo said:
Better at failing. Better at leaking their "cable" onto the pads and ruining them permanently. Better at resisting the user's attempts to maintain or repair them, or even just change the hose length to fit the bike.

If you prefer things to be disposable, then hydraulic bike brakes are for you.

If you'd rather have a bike that stops well all the time and is easy to work on, Avid BB7.

I did not know that was a problem with hydraulics for bicycles. I’ve never owned any but my assumption was they would be good, just like they are on cars and motorcycles. Thanks for the heads up!
 
rick_p said:
Chalo said:
Better at failing. Better at leaking their "cable" onto the pads and ruining them permanently. Better at resisting the user's attempts to maintain or repair them, or even just change the hose length to fit the bike.

If you prefer things to be disposable, then hydraulic bike brakes are for you.

If you'd rather have a bike that stops well all the time and is easy to work on, Avid BB7.

I did not know that was a problem with hydraulics for bicycles. I’ve never owned any but my assumption was they would be good, just like they are on cars and motorcycles. Thanks for the heads up!

Man, we wish we had the same level of reliability and standardization among bicycle hydraulic brakes as with motorcycle and automotive brakes. But these a-holes can't agree on hydraulic fluids, bleed fittings, reservoir or no reservoir, hose diameter, or anything else. And they don't have to-- the things are toys for folks who don't know better to throw money at.
 
I’ve never had any of those catastrophic scare me away problems with hyd. Maybe after I try to shorten a brake line ha ha. Just leave em.
I’ve often thought it would be neat to convert the plastic lines to nice hard coated steel automotive brake lines using appropriate flex sections and adapters to make it work with bike caliper/lever. Using the correct flare tool needed and anchoring the lines appropriately is a must. Ok so motorcycle brakes. No still keep the small sleek bike parts just the lines. You’d have the ultimate brake lines for the zombie apocalypse or land speed record or whatever you’re into. I’m thinking it would be like a functional steam punk look. As ideas are cheap I myself will never do this.
 
Skaiwerd said:
I’ve often thought it would be neat to convert the plastic lines to nice hard coated steel automotive brake lines using appropriate flex sections and adapters to make it work with bike caliper/lever.
Keep in mind that each additional adapter/fitting/connector/transition adds an additional failure point.
 
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