20" Bmx to electric

Fvrdol

10 mW
Joined
Jul 3, 2022
Messages
21
Hello to all,i need help . I would like to convert my bmx 20" to electric. So i need any advice from you.
A loot of questions is in my mind like single gear bike,whatto put hub or mid drive .... Do i need single cog.... What w i need ...please help
 
What specifically do you want the bike to do for you, under what specific conditions?

For instance: how fast you want it to go, and how far do you want to go at that speed, on what terrain (including the slope and length of any hills), what kind of roads or paths (paved, rock, sand, etc), riding style (hard acceleration, slowly getting up to speed, start/stop traffic, continuous riding, etc).

Which specific bike do you have? They're not all identical, and some may have features or specifications that require different parts to convert it than others.
 
I have 20" bmx wethepeople. My main thing is to go with bike to work and home. 8km one way. And it has some uphills so for me speed will be nice ih i go 30km/h and can make on trottle 30km .
Mostly time i drive it on asphalt.
I do not know from where to start
 
Is it steel or aluminum? I've looked into it a little, thinking it would make a good pit bike. Rear dropout spacing is something you need to check on if you want a rear hub motor. Not an issue if you went with a front hub. Steel frames allow for a little stretching/spreading of the dropouts to get the motor to fit. If you use a mid drive, your bottom bracket matters, since most BMX frames would need an adaptor to use motors like the Bafang or Tongsheng mid drives.
 
This bike? Aside from the issue with the single gear, have you thought about where you would mount a battery on the bike? You don't need a large battery for 9-10 miles round trip, maybe you could put the battery in a saddle bag hanging off of the seat. Anything else you are carrying to and from work would have to be in a backpack.

I prefer to carry my laptop and work stuff in a pannier on a rack than on my back. I think for commuting, you would be better off finding an old hardtail mountain bike that you can mount a rack on the back.

607323a4c685438c92a474b0_WTP_MY21_CRS_20_galactic_purple-01-on_white.jpg
 
RunForTheHills said:
This bike? Aside from the issue with the single gear, have you thought about where you would mount a battery on the bike? You don't need a large battery for 9-10 miles round trip, maybe you could put the battery in a saddle bag hanging off of the seat. Anything else you are carrying to and from work would have to be in a backpack.

When I was looking into it, I was looking for a long top tube steel frame, with 1 1/8" head tube, and very little triangle. The plan was to replace the fork with a 110mm front suspension fork, which would relax the head angle (and maybe make the bike more stable, instead of twitchy, at higher speeds), but also allow me to mount a Hailong pack under the downtube. The frames I've seen that meet those specs are expensive, so just casually keeping an eye out. The other option was 24" BMX, which also seem to cost a lot. I also thought of using a 100mm front hub in the rear, and changing the side cover to allow a single speed freewheel to be added to it.
 
E-HP said:
When I was looking into it, I was looking for a long top tube steel frame, with 1 1/8" head tube, and very little triangle. The plan was to replace the fork with a 110mm front suspension fork, which would relax the head angle (and maybe make the bike more stable, instead of twitchy, at higher speeds), but also allow me to mount a Hailong pack under the downtube. The frames I've seen that meet those specs are expensive, so just casually keeping an eye out. The other option was 24" BMX, which also seem to cost a lot. I also thought of using a 100mm front hub in the rear, and changing the side cover to allow a single speed freewheel to be added to it.

I can maybe see it in your application as a pit bike. But for commuting 5 miles each way to work, I wouldn't want to ride that bike. It only has one brake in the rear, the seat height doesn't allow for comfortable pedaling, the steering will be twitchy, and the one low gear will not allow for much pedaling anyway. Even if you could mount a rack on it, I bet your heel would keep hitting any pannier mounted back there. If you are going to invest $1000 into a motor kit and battery, you may as well put in another $200 to buy a decent donor bike on Craigslist. For a commuter, you also need to buy lights, a lock, and optionally a rack and pannier.

I have a Brompton with 16" wheels that I used to use for commuting. The steering is twitchy like the BMX, but the saddle goes high enough for comfortable pedaling, it has a front luggage block I could mount my laptop bag on, and it has six gears. Still, once the building I worked in installed installed bike lockers, I rented one of those, switched to a full size bike, and only rarely road the Brompton into work after that.
 
Yes it is steel 20" bmx from wtp.
She is good for pedaling becouse i put banana seat with sisy bar. Under banana seat i would put batteries which i will make by myself.
I need help which motor mid or hub to buy. Which is better ? How much power? Do i need single cog to buy?
 
I think you may find it challenging to mount a mid-drive with the press-fit bottom bracket on that bike. The O.L.D. of the rear hub is 110mm and the O.L.D. of the front hub is a standard 100mm. Any front hub laced into a 20" wheel will fit that bike and that is probably what I would use. I think that it would be hard to find a rear hub motor to fit that bike. The O.L.D. of a standard bike is 135mm. That is a steel frame, so it might be possible to spread the rear dropouts some, but 25mm (1 inch) would be a lot and I wouldn't try that.
 
Can you send me link for the press-fit bottom bracket which fits withbafang mid drive for that bike? I do not know how it looks like, i am tottaly amater, So i will see to try to focus on mid drive motor
 
I am not sure what you are looking for. The current model year of that bike uses this bottom bracket:

https://www.danscomp.com/salt-plus-...cket-black-19mm-45095010514/p1205296?v=431061

Of course, you will have to remove the bottom bracket to install a mid-drive motor. Mid-drive motors are designed to work with 68-73mm wide jis-bsa threaded bottom brackets. You will need to get some kind of adapter to make it work with your bike. I don't really have any experience with that. Maybe someone else here who has done it can comment on it.

MTA: The bottom bracket is described in the specs as "SALT "MID" bb, 19mm, press fit, sealed bearing". It doesn't say what the shell size is, so you will have to measure that.
 
A mid drive on a 20" wheeled bmx would be a sight to see.

Hub motor on a 20" wheel would mean a radially laved or 0-cross lacing of the rim, even perhaps a 22" but you'd just go to the spoke calculator link at www.ebikes.ca to see things clearly, lots of good info on there on everything ebike. Go check it out, yes you whos reading this now new to the fun hobby of riding ebikes and building ebikes. It sure is a great way to get some physical acitivity with very low impact on the joints which is why they are so popular with older folks locking their multi-thousand dollar ebike up with a cheap fuking lock.

How tall are you?
Do you know about the 22" bmx wheels as well that match up to motorcycle rim sizing of ????
Luckily its listed by Spinning Magnets online article but more importantly, Eric has Google-Fu, the ability to put his links at the top of search terms.
3rd link in on "bicycle rims to moped rims" - https://www.electricbike.com › moped-rims-tires-hubmotors
Link is dead, my internets still up was a live link not long ago. Hope Eric is on the ball with his internet server, I could only assume or outsourced is more common.
 
I am 1,75 cm so i fit in my bmx bike 20" with banana seat. And i am 80kg
I am starting to put batteries under banana seat it has enough place.
The question which i do not understand is which motor will be best to fit to 20" bike
 
A mid drive on a single speed is not a wise idea, defeats the entire purpose of a mid drive system for ebikes. People are doing it.
Any hub motor is fine, just depends on the terrain, wind and other factors and top speed you want.
Check out the simulator and plug in your route and see, analyze it, study it, post about it and buy it.


Fvrdol said:
I am 1,75 cm so i fit in my bmx bike 20" with banana seat. And i am 80kg
I am starting to put batteries under banana seat it has enough place.
The question which i do not understand is which motor will be best to fit to 20" bike
 
Fvrdol said:
Hello to all,i need help . I would like to convert my bmx 20" to electric. So i need any advice from you.
A loot of questions is in my mind like single gear bike,whatto put hub or mid drive .... Do i need single cog.... What w i need ...please help

The small wheel diameter of a BMX bike plays to the strengths of a hub motor.

If you're using a single speed pedal drive, there are only disadvantages in a mid drive, and no advantages.
 
Then i need rear hum motor kit with 110mm at rear o.l.d.
If anyome has idea where to find thst kit please replay
 
Fvrdol said:
Then i need rear hum motor kit with 110mm at rear o.l.d.
If anyome has idea where to find thst kit please replay

Or you could just put a front hub motor kit on it and be done with it. It will get you to work and back. You can buy them already laced into a 20" wheel for under $300 without the battery. Why take the path of most resistance?

Putting 1000 watt motor on a bicycle with one brake in the rear and twitchy steering is a really bad idea. That bike isn't going to feel or be safe above 20mph unless you are an adrenaline junkie. Honestly, I would find an older hardtail mountain bike to convert. They are easy to find, make much better commuter bikes, and you can put any kind of kit you want on it.
 
Fvrdol said:
Then i need rear hum motor kit with 110mm at rear o.l.d.
If anyome has idea where to find thst kit please replay

You could probably go with a standard width motor between being able to spread the dropout width a little and when you fabricate new dropouts that match a hub motor axle. Do you have a welder?
 
I am open for every advices... Nice idea front wheel.. so i need go buy hub motor with single speed?
Whole afternoon i was searching fromt hub motor 20" for single speed and i lost my eyes without suxcess
In my country we have a loot uphill and downhill so can you tell me how front wheell did on uphill?
 
Fvrdol said:
I am open for every advices... Nice idea front wheel.. so i need go buy hub motor with single speed?
Whole afternoon i was searching fromt hub motor 20" for single speed and i lost my eyes without suxcess
In my country we have a loot uphill and downhill so can you tell me how front wheell did on uphill?

I am not sure what you mean by single speed motor. Geared hub motors that have more than one gear are very rare. You will adjust the speed with the throttle or PAS assist level and how much pedaling you do. You can either get a direct drive (DD) hub motor or geared hub motor. Geared hub motors are lighter and more efficient in their designed speed range, but DD motors can take more abuse than a geared hub motor and can do brake regen.

https://www.ebay.com/itm/115024754588?epid=13037986380&hash=item1ac802779c:g:3GkAAOSw21NfG9xn
https://www.amazon.com/EBIKELING-Wa...ike+kit+front+wheel,aps,156&sr=8-4&th=1&psc=1
 
https://www.leafbike.com/products/diy-bike-conversion-kit/20-inch-48v-52v-1000w-rear-bmx-hub-motor-bike-conversion-kit-1151.html

Look what i find...kit which can fit in rear bmx frame only you need single cog

Main problem is that the delivery is tooo expensive
 
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