Convert from DISC brake to RIM brake

Current situation: I have a hard-tail mountain bike equiped with Mac 10t motor and a 52v (14s) battery that I have been riding as a commuter bike since 2014. I ride around 20-25 miles per day at a pace around 15-20 mph with this setup, and it has mostly worked well for me.

The once exception is the experience of fixing a tire on the road when I get a flat. It always happens in the dark when it's raining, and it's quite an ordeal due to my glasses fogging up, the need to hold a flashlight, the weight of the rear wheel, and the tight clearance of the rear disk and the need for spacers needed to get the correct alignment. In general, I struggle to get it back together so that is is aligned properly.

I think that this would be easier to handled with rim brakes on the rear, but I haven't been able to find a solution to convert a bike with disc brakes back to rim brakes. Note: my frame doesn't have braze-ons for the calipers, so it seems my only option is to get a new frame, but I'm open to other suggestions. The other option that I've considered is keeping the disc brakes and doing a mid-drive conversion.

Thanks,

dancliff

Why do you need spacers to get the disc rotor aligned? Are they on the axle, the caliper, or the rotor?

Rim brakes are also subject to alignment issues when the wheel is installed. If you are having difficulty getting the wheel to set up consistently every time you install it, then that's the problem you should try to solve.

I go out of my way to put the most puncture resistant tires I have available on hub motor wheels. Not all the people I build e-bikes for are capable of dealing with a flat when they're out on the street.

What about alternate tire solutions to avoid getting flats? Tubeless + Sealant (lots of hardcore sealant since weight isn't your concern here), Foam inserts that go outside the tube (to stop what I assume are sharp objects getting deep enough to get to the tube), sealant inside the tube, puncture resistant tubes. None of these will totally eliminate punctures but could dramatically reduce them and some (sealant) will change the event from replacing a tube to just pumping it up and waiting for the sealant to do it's job, the latex + tons of rubber chunk and fiber sealants can seal holes made by amazingly large pointy objects.

Other ideas would be bring a small headlamp instead of a flashlight to free up a hand. Are they cable or hydro discs? I've never used cable discs but I have a suspicion they may have a much larger gap between the pads when open if adjusted as such.

As for rim brakes while I assume you're about to get some comment(s) about how rim brakes are great. I personally would never use rim brakes again for the sole reason they don't work as well when they get wet and while I'm sure some fancy pads improve this I can't help but think they will never be as good at stopping when wet than discs.

@Chalo

I use spacers on the axle to get the chainline and disc alignment setup correctly.

In general I find RIM brakes much easier to deal with when I change a flat. When I'm at home in my garage, and I can clearly see what I'm doing, getting the alignment is not very difficult.

I had some Schwable tires on the bike for a while, but they weren't resistant to roofing nails, and they were extremely difficult to replace. I've switched to using panaracer tires, which I can replace without tools.

@scianiac

I've tried sealants and liners, which also don't work against roofing nails (too big of a hole). Also the sealant is problematic if it doesn't seal, and you need to patch the tire.

I also have a small headlamp, which I had in my pack and forgot about, and so when I needed it, the battery was dead.

I have avid bb7 cable disks. They work well in general.

I don't want to debate disc vs. rim brakes. Either one has worked fine for me in the past, as long as I keep them setup properly.

scianiac said:

What about alternate tire solutions to avoid getting flats? Tubeless + Sealant (lots of hardcore sealant since weight isn't your concern here), Foam inserts that go outside the tube (to stop what I assume are sharp objects getting deep enough to get to the tube), sealant inside the tube,

Click to expand...

Tubeless would multiply his troubles. Think swapping a tube in the dark and rain is a hassle? Try dealing with a burped or spewing tubeless tire in the same conditions. Plus, latex sealants curdle and dry out, and require periodic changing even if you didn't get a puncture.

Sealant in a tube is not a bad idea, and when things go very wrong you can just throw it away and start over.

dancliff said:

In general I find RIM brakes much easier to deal with when I change a flat. When I'm at home in my garage, and I can clearly see what I'm doing, getting the alignment is not very difficult.

Click to expand...

I have the opposite experience. I find it very easy to drop the rotor into the slot in the caliper; that lines up the wheel nicely to go into the dropouts. And no having to release the calipers to get the wheel to go in or out.

Converting to rims is going to be difficult. By far the best way is to have brazeons added for your favorite flavor of brake - I'd recommend V-brakes. This is easy on steel frames, harder on aluminum frames.

If that's too hard for you, your next best option is going to be a new frame. There are tons of frames out there with the right brazeons for rim brakes, and of course your front fork is replaceable to support any sort of brake you want.

I have seen kits that allow you to add brakes to some frames, but the frame has to have the right kind of geometry. One such kit allowed conversion of a caliper brake (i.e. a frame that already had that crossbar over the wheel on the seatstays) to V-brakes, but it only worked for specific frame tube diameters. You are unlikely to find one of those that can work for you.

Your final option is to build an adapter, but that takes some serious machining skills, and not something I'd recommend unless you are already a machinist.

So those roofing nails seem to have thwarted all or out ideas and I assume moving somewhere with less roofers is not an option. I don't recall seeing any good options for solid or airless tires so it's back to rim brakes. Could always make the motor locked and just use regen and no rear brake but there are some issues there....

So if I were to try and retrofit some rim brakes I would go about it like such. First I would laser cut (from sendcutsent.com) a nice thick horseshoe mount like on the old hardcore MTB rim brakes, this will mount both the pivot point things (I have very little experience with rim brakes so I'm just making this up). This will also keep them nice and stiff and then we can mount this plate to the seatstays possibly with just some U-bolts and 3D printed spacers to fit them around the tubes nicely. This all assumes the frame is strong enough to support the load there.

Tubeless would multiply his troubles. Think swapping a tube in the dark and rain is a hassle? Try dealing with a burped or spewing tubeless tire in the same conditions. Plus, latex sealants curdle and dry out, and require periodic changing even if you didn't get a puncture.

Click to expand...

Fair enough, my MTB experience does not always apply well to commuting. There are latex free sealants but they don't work as well, I've been running a mix of latex and heavy filled latex free and experimenting with adding more latex or just more ammonia (the latex doesn't dry out the ammonia dries out which is what is keeping the latex in suspension).

It is your wheel alignment that you need to work on. The simple and only solution is to make it a permanent fit. Hub builds need torque arm or torque plates, or custom dropouts. When alignment is a problem, forget the torque arm. Bolt-on torque plates, or custom dropouts, are giving you the opportunity to tune the alignment once and for all because the fit and thickness can place the wheel exactly where you want it. The time spent cutting and filing the plates/dropouts, is well rewarded with simple and quick further wheel maintenance, and safety for future power upgrade and/or regen.

You think flats are a hassle? I replace tires every 6 week average, because of the high power that I feed. Yet I do it in 10 minutes. Tubeless is good when done properly: tubeless rated rim and tire, with Cush Core inserts. Expansive but very reliable. Fixing a flat with a tubeless plug in 5 minutes in the dark, or even riding home on the flat because the Cush Core insert is letting you do that up to 15 mph without any risk of tire popping off the rim, while providing enough cushion to save the tire from any damage.

I don't have the fabrication skills to create custom mounts, dropouts or flange plates, so not good options for me.

It's been quite a while since I built the bike, but I now recall that the need for the spacers might be driven by the fact that I put a larger rotor (205 mm IIRC) on the back wheel. As it is now, the rotor barely clears the frame. I think that I might experiment with going back to the original 160 mm rotor and see if I can remove the spacers.

Getting a different frame might also be a good option. Any recommendations on places get a decent frame at a reasonable price?

While researching this topic, I came across the tubeless inserts. They look interesting, but I'm not sure if they would work with my rims. Is it possible to convert from tubed to tubeless? Note: I have Alexis dm24 rims from em3ev.

Install a new fork with disc and rim brake mounts, or just rim brake mount but I'd look for a fork with both. Most of the braking is done with the front brake, next solution for braking is direct drive, or GMAC electric braking or regen braking. If your lucky you can talk to some local bike stores and they know someone who can weld/braze bicycle frames to do brake post mounts.

Why would you want to remove the wheel when fixing a flat (inner) tire?
Just leave the wheel in place, lift outer tire off the rim, pull out the inner tire, fix it, put back in outer tire, put tires on rim and inflate...

I carry extra tubes. There are tubes that can be replaced without wheel removal.

ZeroEm said:

I carry extra tubes. There are tubes that can be replaced without wheel removal.

Click to expand...

https://www.flybikes.com/product/cobra-tube

It looks like a good idea, at least as a temporary fix to get home, but I read that they were discontinued.

However, I did find these: https://www.amazon.com/Huffy-Bicycle-Company-Quick-Change/dp/B07MXLDSLK

It's what a person wants todo. I dabbled with slime but it plugs up the valve stems and makes a mess. does not get rid of that piece of wire in the tire.
Everyone does not have the same issue with flats. Some have it bad. I had a small piece of wire from a radial tire three years ago gave me a slow leak. Put on Schwalbe Marathon Plus and no more flats. It's not magic spend most of the time on greenways no nails or goatheads.

So I carry enough tools to get my wheels off and tubes and bike pump. Hope I never need them.