E-bike without rear disc mount

[Smurf2]

Hi. I build my ebike started from forum here:

Help me build e-bike (mtb)

Guys. I made first run yesterday evening, and can say that motor is very good. No one bridge can stop me! :) Speed 35km/h and 37km/h top speed. But measure with gps, it's been little lover than that. Going up on bridge with minimum 31km/h :) Feel some vibration when starting, think they come...

endless-sphere.com

It is more than 1 year and working fine, for now.

I noticed that my rear rim start wear and create a little channel. So, before I destroy it, I want switch to mechanical disc brakes (from V-brakes).

Need only caliper, disc/pads and adapter(using existing hand levers), right?

On back rim (hub motor) I have 6 holes, think that is fit for standard disc size.
Don't have yet front rim with holes for disc, must buy it.

Holes at front holder caliper are around 51 mm (it seems standard).

But problem is that back holes on fork (needed for caliper) are around 20 mm. It seems that not for caliper, for what they are? Rack?

I can drill extra hole +20mm for install adapter and caliper there.

Or I can order adapter BRACELET , which tightens around fork. But saw on YT that after some time bracelet moves and need adjust it.

Which option you recommend me?

Don't know many about bike disc, so any information will help.

 

[glennb]

You deserve top marks for creativity, lateral thinking, economising, researching, and most of all for being humble enough to request outside expertise to assess the solutions you’ve devised.

Do you know the expression: “the devil is in the detail”?

To work well, the parts need to be fabricated specifically for your frame, to a degree of precision that is too impractical to be worthwhile.

And even then, the best solution that you can implement for that frame is still inferior in every regard to swapping the frame for one with disc tabs.

The fact that you can get a slightly used equivalent disc brake frame for anything between $0 and $50 makes all other options non-worthwhile.

I understand that you have time and effort invested in this bicycle, and that you’ve had good times together and you understand and trust it. However, if you want disc brakes your requirements from the frame have altered significantly enough that you should set aside any emotional attachments to it.

 

[docw009]

You can redo another torque plate, and make it bigger so you can attach a disk brake caliper. It also has to be thick enough not to bend.

You can also buy adapters, but you will still have to machine them to fit. I've used this one on both the front and rear of my conversions, but I had to modify it so the motor axle would slide in like a dropout. Each install is going to be different. Check the reviews for ideas.

Bikeberry Adapter sold on Amazon



Here is another type. It was designed to clamp over the frame. Works good for regular bikes with skewer type axles.Unwieldy for a motor because you have to unclamp it. I also modified so a motor axle could slide in, Also added mounting bolts to screw it to the frame. Not shown is a cross brace that pushes against the chainstays.

Chinese Disk Brake Adapter



Finally, it's a good idea to add a brace on the first one too. so that when the adapter tries to twist forward when the brakes are applied, it will push against the frame.

 

[2old]

Another option, since you're creative, would be to rebuild the rear wheel and maybe use Kool Stop pads on the brake calipers. The rear brake isn't nearly as important as the front (IMO) so you could change the front and be OK.

 

[Chalo]

I noticed that my rear rim start wear and create a little channel. So, before I destroy it, I want switch to mechanical disc brakes (from V-brakes).

Many modern rims have a groove in the sidewall as a wear indicator. That's what I think I'm seeing in the photo. Certainly if you haven't gone through half a dozen or more pairs of brake pads, and haven't let the pads wear down until the steel cores start cutting into the rim, your rim probably doesn't have any significant wear from braking. So I think your concern is unfounded.

My advice is, don't try to retrofit a disc brake. Your frame doesn't have the right mounts for one, and scabbing on some hokey adapter will not work as well as you think. But it will make wheel changes and wheel alignment much more of a problem.

If you think you don't have enough braking power available, first switch to new brake pads. Kool Stop black, "Salmon", and "E-bike" (gray) compound are all very non-abrasive to aluminum rims and have great friction coefficient and long wear life. If the brake arms aren't super cheap and horrible, you can get harder and more reliable braking from this approach than from any mechanical disc brake.

So if just new pads and a good smooth fresh cable don't do what you want, the next step would be a nicer brake (like one that retails for $20-40). Next step after that would be to add a brake booster arch, though this is seldom helpful for a rear brake.

Putting a disc brake on the front is straightforward, just use one with IS mounting. But it won't be as strong as a decent V-brake with good pads and cable.

If both your brakes are fitted with these:

Amazon.com

and these:

Amazon.com

and set up and adjusted correctly, you won't have any reason to buy a front wheel or mess around with disc brakes that need more frequent attention, make more noise, and become much more easily contaminated.

 

[Smurf2]

@docw009
Thanks for that examples and links, I will study that !

@Chalo

That's what I think I'm seeing in the photo.

How can you see in photo? I am not posted 'used' rim in zoom yet.

If you think you don't have enough braking power available

No, no, don't need braking power. I don't want rotating over myself, guys! Just want to avoid wear of rear soft rim. I think that I have first time pads from old bike, which pads was too hard (sound like you grab iron to iron) and that cut inside a rim. Now my newer pads are at like 45 degrees (see picture) because that channel.

@2old

The rear brake isn't nearly as important as the front (IMO) so you could change the front and be OK.

Don't know for you guys, but I am braking like 90% with rear. I mean at 45km/h on my bike is not safe start brake with front, because I will rotate around myself! So, I start braking with rear, and when I close the stop target, I slow push front brake to stop full.

But I use too often brake (I slow to 99% on each hole or house entry, risols, etc.), because shaking electronic and tyre guard (5 puncture in 14 months!), in that way my pads wear to fast, and need discs.

Overall, is good to be both disc same sizes? That means that I can start from front, where I can 51mm space mount holes. Is better 180 disc size for ebike?

But I don't understand why adapters are so stupid classified, I mean they are without space mount data. So how do I know which adapters have 51mm holes ???

When find setup (which exist) for first fork, then I can try to find same size adapter/bracelet, with same holes, which fit for same calipers?

Now I add zoom pictures of rim, you can't see too much, but can fill 'chanel' with finger. The red marks show some line (maybe is that wear indicator?).

 

[amberwolf]

I noticed that my rear rim start wear and create a little channel. So, before I destroy it, I want switch to mechanical disc brakes (from V-brakes).

I don't see any significant wear. Could you take a picture of the wear you are seeing? The only thing I see is the wear-indicator groove that Chalo refers to.

EDIT: your new post with the pics just showed up as I clicked Submit on this one.
There's some wear; I can't tell if it's really bad, but the pads are severely misaligned and are definitely badly worn from it. See here for info on aligning them and setting up your brakes (I'd start with new pads, though).

Adjusting Direct-pull Cantilever Bicycle Brakes ("V-Brakes ®")

A practical guide to adjusting direct-pull brakes ('V brakes')to get the best braking performance on your bicycle.

www.sheldonbrown.com

Bicycle Rim Brakes

A practical guide to the different types of rim brakes for bicycles: how they work, choices, adjustment.

www.sheldonbrown.com

But problem is that back holes on fork (needed for caliper) are around 20 mm. It seems that not for caliper, for what they are? Rack?

Probably.

I don't really recommend those "bracelet" things; they can work but they may not stay in place over time, and some of them are made of pretty thin and/or bendy metal so the calipers don't stay aligned. (to be fair, this is also true of some of the tabs on cheaper bike frames and forks)


If you really need rear disc brakes (probably not--follow Chalo's advice and you'll get braking that will be better than you can use all of), you can make your own torque-plate / disc adapter combination that bolts to those rack holes. See the other posts people have made above for examples. The Torque Arm Picture Thread has a number of examples in it, too.

If you do require disc brakes, I'd recommend the Avid BB7 MTN calipers; a single one on the front wheel of my heavy heavy-cargo SB Cruiser trike is easily able to skid the wheel (more braking power than I can use) if I pull it hard, so even one on your bike's front wheel would easily be more stopping power than you can use, and you wouldn't need to modify the rear.

If you use them, I recommend also using the Avid Single-Digit lever to control them, as it is adjustable to your needs and works well.

If you want nice smooth cable operation, you can use Jagwire cable and housing; it's been reliable.

 

[amberwolf]

But I use too often brake (I slow to 99% on each hole or house entry, risols, etc.), because shaking electronic and tyre guard (5 puncture in 14 months!), in that way my pads wear to fast, and need discs.

FWIW, you'll probably have faster pad wear on the discs; you may wish to carry a spare set. Semi-metallic on the BB7s will probably work best; I recommend either the Avid or Koolstop pads.

Make sure that when you buy the BB7s (or whatever you get) that you are actually buying genuine parts--there are plenty of fakes out there, and lots of stuff on amazon and ebay and the like that uses Avid or BB7 in the title or description, but even the pictures they show are not of those brakes, and are just generics that are probably not nearly as good or well-made.

Same for the pads--don't get the generics; they may work but they'll wear faster and are not as good. (already tried this to save money).

Overall, is good to be both disc same sizes? That means that I can start from front, where I can 51mm space mount holes. Is better 180 disc size for ebike?

The bigger the rotor, the greater stopping power for less pad force; it's likely that in the rear you can only use so much stopping power before the wheel skids. If you are not having that problem now, with good pad grip on the rims, then you can use larger rotors' full power.

But I don't understand why adapters are so stupid classified, I mean they are without space mount data. So how do I know which adapters have 51mm holes ???

If the tabs on your bike are ISO, then all of the adapters for ISO will fit them. You can look up your bike or it's fork on the manufacturer site and possibly find this out, or you can look up the ISO standard for the tabs to see if they match.

In other cases you may run into the problem another user did here:

IS Mount Misalignment 160mm vs 203mm

While I'm working on my torque arm extension, part of the setup is replicating the rear wheel IS Mount (aka I.S. Mount / International Standard Mount / ISO Mount / forum-search-term-stuffing) on the extension arm. However, in both this design and the previous version, the mounts seem to work...

endless-sphere.com

 

[99t4]

From those last photos, it sure looks like your brake pads have been improperly aligned for a long time. When the pads contact the rim the entire surface of the pad should make full contact with the flat surface of the rim, not half falling off the edge of the rim like yours are.

Should be aligned like this:

Yours are not correctly positioned, like this:



That will degrade braking performance, and can cause uneven wear of the pads and the rim.

 

[Chalo]

Take a look at the working surface of the pads. If there is any metal showing through, then that, and not normal brake surface wear, is what bit your rim.

Note that the rims that come laced to hub motors are almost invariably the cheapest, lowest quality rims that look approximately right. So if the manufacturer used an alloy made for window trim or beverage cans, that's not really a surprise.

 

[Smurf2]

@99t4

looks like your brake pads have been improperly aligned for a long time. When the pads contact the rim the entire surface of the pad should make full contact with the flat surface of the rim, not half falling off the edge of the rim like yours are.

@99t4 and @amberwolf
Yes, I know that. I installed them at 6.2023., and it seems right pad was move, and I am figure out that too late which results pads at 45°. Now aligment is good.

If I buy just new pads, maybe rim will deform pads in shape again, because existing chanel.

For brands, I don't have many options in my local store..They are very very limited. They force Shimano and Tektro hydraulic brake the most. But I need mechanical.

Let say idea is to buy 2x 180mm disc with same brand calipers, right?
I can try with this rear adapter, which work against the fork. If adapter will be too thin, I can extend it.

https://a.aliexpress.com/_mPwCD4q

At Amazon, one set of Avid bb7 are 60-70€ included discs. Two of them are 140 € + postage. That is a lot??
(Keep in mind that I bought whole bike for 112€!).

I can try find on ebay.co.uk, amazon.de or Aliexpres. All life I buying from Aliexpres (included my ebike conversion). They have pretty nice and cheap sets, which will braking like other expencive brands. That idea will not support @amberwolf, and other which preffer just original parts

Is there some cheaper version than Avid bb7?

 

[Chalo]

Is there some cheaper version than Avid bb7?

There are many cheaper cable disc brakes. They're all weaker, more of a hassle to adjust, and more likely to rub than BB7.

If cost vs performance is a factor to you, rim brakes will win 100% of the time.

 

[Chalo]

Tektro Aries cable disc brake is super common on ready made e-bikes and rental e-bikes. It's pretty durable, pretty easy to live with, not terribly impressive but not bad. And it's cheap.

 

[99t4]

My forecast: You will not get good results from a disc brake conversion requiring a caliper mounting adapter.

You need to replace the damaged rim anyway. Those rims are low quality and fail there (they crack apart right where yours is excessively worn) often, even without wear from rim brakes.

For the same price (or less!) of converting to disc brake (with disappointing results), you could rebuild the wheel with a good quality rim and better spokes, install improved brake pads, and enjoy high performance braking.

Especially if you learn to use the front brake correctly and safely.

BTW your handgrips are installed backwards. (Unless you did that on purpose for your own reasons.)

 

[Smurf2]

@99t4

You need to replace the damaged rim anyway.

Not sure that I can change spokes on other "aluminum" rim and Hub Motor. It is a lot of precision work. (Btw that rim with motor is 260€.)

@Chalo

Tektro Aries cable disc brake is super common on ready made e-bikes and rental e-bikes.

Do you mean hydraulic?

Can't believe that mechanical brake are so rare, only few of them on amazon.de, and with disc in set also few.

I found this set. Reasonable price with shipping.

But, example of caliper specifications:
"F160-R140 (front brake), F180-R160 (rear brake)."
Why is that? So that caliper can't be installed with disc of 180 front and 180 back? or can?

@99t4
Thanks to tip. I am not found any manual how to install that handgrips

 

[Chalo]

[Not sure that I can change spokes on other "aluminum" rim and Hub Motor. It is a lot of precision work.

You can do it. Not as well as a seasoned professional, but it's just hand work and attention to detail. Look at Sheldonbrown.com's material on wheel building. It's the most concise yet adequate instructions I have seen.

Do you mean hydraulic?

Can't believe that mechanical brake are so rare, only few of them on amazon.de, and with disc in set also few.

No, Tektro Aries are definitely cable brakes. Cable discs are very common; they're just something you usually see on cheap original equipment. People who buy brakes by themselves are overly impressed by needless hydraulics, so that's where the profit is.

There are lots of choices of cable discs less than $50. Some (like Promax) are super crappy. Others like Tektro are not bad. Avid BB5 and Shimano mechanical discs are uncharacteristically mediocre, probably sabotaged to make their cheap hydros seem less lame.

Hydraulics less than $50/brake are extremely suspect, leaky, unreliable, non-versatile. If the hose isn't the right length, or you can't route it without opening the system, it might cost you more to install it than the brake costs.

But, example of caliper specifications:
"F160-R140 (front brake), F180-R160 (rear brake)."
Why is that? So that caliper can't be installed with disc of 180 front and 180 back? or can?

International Standard (IS) brackets are the same for front or rear, but they fit different sizes front and rear. If you get the wrong one, you don't need to find another caliper; you only need to find a different bracket. Post mount brakes use the same caliper without the bracket, and are dedicated to a single size (though you can get fiddly adapters to retrofit to a larger rotor).

Flat mount brakes are accursed, incompatible with better systems, and if you need them, you bought the wrong frame.

 

[Smurf2]

Aha. I am interested in mechanical disc brake. Not hydraulic.
I think that someone wrote that wear is similar with normal brake shoes and disc brake pads?

I drive this year almost every weekday 45 km (at good weather). Much braking. Rear shoes bought at 6.2023. and almost gone. Front bought a couple of months before and still in good condition.

I mean, the disc is made from metal, and disc brake pads can't last longer than normal brake shoes ?

International Standard (IS) brackets are the same for front or rear, but they fit different sizes front and rear. If you get the wrong one, you don't need to find another caliper; you only need to find a different bracket. Post mount brakes use the same caliper without the bracket, and are dedicated to a single size (though you can get fiddly adapters to retrofit to a larger rotor).

So, that front rear not matter like they describe. I can buy just adapter, and if says 140/160, I buy ISO adapter for 180mm? One Caliper can work for all sizes disc?

 

[neptronix]

Honestly dude, that looks like significant wear on your rim so far..
I take it you live in a hilly area and that's a geared motor that has no regen capability..
Just guessing!

I would not consider an off the shelf disc brake adapter at all, braking forces are many times stronger than acceleration forces and any amount of 'play' is unacceptable.

If you are in a hilly area as i think, i would suggest getting a motor with regen braking. Regenerative brakes don't wear..

 

[99t4]

Not sure that I can change spokes on other "aluminum" rim and Hub Motor. It is a lot of precision work. (Btw that rim with motor is 260€.)

Most all rims that are on prebuilt motor/wheel kits are poor quality. They crack even when used with disc brakes (no rim brake wear). Yours is appreciably worn making it more of a risk. Why risk it? For example, mine cracked with no sidewall wear. I caught it before it cracked further. The tube can pop out, explode, throw the tire off the rim, potentially causing loss of control. I rebuilt it (first time for me also) with good quality rim and spokes following advice from this forum, and these three helpful videos (at the bottom of the page):

Wheel Building - Learn

There are many good print and online references for lacing bicycle wheels. Many will defer to Sheldon Brown, Brandt's Bicycle Wheel Book, and others. However, a lot of the points and details with a conventional bicycle hubs don't necessarily apply to hub motors with their much larger flange...

ebikes.ca

 

[Chalo]

Regenerative brakes don't wear..

Not until you spin an axle, anyway.

 

[neptronix]

Not until you spin an axle, anyway.

With an adequate torque plate that will not be a problem.

I used to run 1000W regen on my 6kW bike.. no problem.

 

[Smurf2]

@neptronix

I take it you live in a hilly area and that's a geared motor that has no regen capability..
Just guessing!"

Hey. I will just repeat for you how I drive, to be clear.

Yes, I'm living in area of middle hills, but that is nothing have with hills.
My almost all drive is flat, from village to city every day, on bad asphalt with too many holes and curbs, 2-3 bridges.
Bike paths are very old. They are not road path, they are out of road, so must go up/down all time.

My ebike drive is something different than you guys. I told that I drive too carefull because saving my battery and electronic shaking/vibrations, also watch to not puncture tyre (5 punctures in 14 months, but let please that for another thread) with avoid glass, wood parts, garbage etc., because that.

When mean careful, I mean:
From full power (or half) slow down to 5-15 km/h, on every:
-traffic light/crossing (3-5cm curbs)
- every house entry (can be 5-10cm high curbs)
- parts of very old rough asphalt and bumps (causes much vibrates).

I know that is funny or strange, but If I had driven differently, battery could have fallen out and the rim bent. And when hit hard the hole with bike, I want cry.

And my hub motor braking a little, but not too much.

 

[neptronix]

Okay, a decent amount of braking, but you don't live on a rollercoaster like i do

Your terrain sounds similar to mine ( awful ) and it sounds like full suspension would make your life a lot easier. Maybe swapping to a full suspension frame can solve two problems for you

 

[Smurf2]

@Chalo
So, that front rear not matter like they describe. I can buy just adapter, and if says 140/160, I buy ISO adapter for 180mm? One Caliper can work for 140/160/180 sizes disc?


I think that someone wrote that wear is similar with normal brake shoes and disc brake pads? Which will win?

 

[Chalo]

@Chalo
So, that front rear not matter like they describe. I can buy just adapter, and if says 140/160, I buy ISO adapter for 180mm? One Caliper can work for 140/160/180 sizes disc?

That's right. Any IS caliper mount will work front or rear, but the matching rotor will be 20mm larger in front than in the rear.

I think that someone wrote that wear is similar with normal brake shoes and disc brake pads? Which will win?

That depends entirely on the specific pads you're comparing. "Organic" or "fiber" disc pads tend to wear quickly, but sintered metal pads can last a very long time. For rim brakes, cheap OEM pads usually wear quickly, Kool Stop "Salmon" or "E-bike" pads are very long lasting.