Help and guidance replacing rum on motor hub

[CookFLHX]

Hello! I’ve recently acquired three e-bike conversion motorized hub wheels. Currently, they are outfitted with 26”, very skinny road tire rims. These rims won’t work for my application. The tires need to be a least a good mountain bike width, or even 3” tires would be better.

I’ve never replaced a rim, or laced and trued a wheel, but from what I have read, it is a very doable project. The main issue is there is a lot of specifics that I’m just not familiar with.

Im going to do it. I’ve already decided. It’s just a matter of educating myself.

In addition to the research I’m doing I wanted to see if anyone was familiar with this. In particular, working with the motorized hubs.
Are there any vendors or resources available that will allow you to provide specs such as hub size in order to get a kit with all the needed stuff? For example, it would be great if there was a kit that included the rim, spikes cut to size, etc.
I’ve found one or two, but if anyone knows of any good resources that can help guide me to install a rim on an e-bike motor hub.

Thanks for your time

 

[harryS]

You will need a spoke calculator, and this is the one I've used, I've done over a dozen wheels,

Online Spoke Calculator for Hubmotors and Ebikes

Our handy spoke length calculator allows for easy calculation of spoke length for custom builds - and is the only one of its kind to include paired spoke holes in the flange as is common with many large diameter hub motors. It also creates an automatic side view drawing of the laced wheel and...

ebikes.ca

The most critical measurement is the effective rim diameter, ERD. For the above calculator, this is measured from the top of the nipple in the rim to its opposite member on the other side of the rim, Sometimes the rim manufacturer will give an ERD, but you have no idea of how it was measured . I have used the manufactirer's ERD twice and ordered spokes that were too long, as a result. Buy the rim first and measure it yourself.

It's tricky to measure with a metal tape measure because you need 1mm accuracy. I saw this method on another forum. He uses two old spokes, trimmed to the same length, Spin a nipple on each end, flush with the end of the spoke, Insert in opposite holes, and measure the gap.

A comment on spokes. Existing hub motors tend to use thick spokes, usually 13G, sometimes 12G. There are arguments from old timer wheel builders that thinner spokes work better, but the hub motors are drilled for 13G. Meanwhile, many rims are drilled for 14G spokes. Spoke makers provide spokes with 13G elbows and 14G ends for this purpose. Sapim makes a good one. Quite a difference in quality between Sapim spokes, and the cheap 50 cent spokes I used to order from China. I ordered spokes from wheelbuilder.com last time.

You want a double wall rim. If your measurements are off, the spokes will protrude past the end of the nipple, but the error is inside the rim. With a cheap single wall rim, that's going to stick into your inner tubes, even with thick rim tape. You can be a little long on your spokes with a double wall rim, as you can also add washers,

There's no real skill to buiding a wheel. High school kids paid 5 bucks an hour used to do it, Just be patient, You don't need a fancy rig. I used an old fat tire fork (135mm) clamped to my bench. You can use an upside down bike frame. Tape a piece of paper across the fork next to the rim. Mark the edges with a pencil and true the rim up, In the end, you'll find that a quarter turn on two spokes can move the edge dramatically,

As for the patterns, a single cross is what hub motors use. Keep one wheel intact and refer to it for hints as you do your first wheel. You'll learn that rear wheels are always dished, i.e, the rim is not in the center of the hub. The spoke calculator foresees that. even if you don't know that,

I followed this youtube vid originally,

 

[fritz katzenjammer]

I would highly recommend going on Sheldon Brown’s site and reading his articles on wheel building. The guy can explain anything in terms mere mortals can understand.

Have a good look around while you are there… because he explains almost everything else as well.

“Sheldon brown wheel building” will dump you right on his doorstep.

 

[CookFLHX]

You will need a spoke calculator, and this is the one I've used, I've done over a dozen wheels,

Online Spoke Calculator for Hubmotors and Ebikes

Our handy spoke length calculator allows for easy calculation of spoke length for custom builds - and is the only one of its kind to include paired spoke holes in the flange as is common with many large diameter hub motors. It also creates an automatic side view drawing of the laced wheel and...

ebikes.ca

The most critical measurement is the effective rim diameter, ERD. For the above calculator, this is measured from the top of the nipple in the rim to its opposite member on the other side of the rim, Sometimes the rim manufacturer will give an ERD, but you have no idea of how it was measured . I have used the manufactirer's ERD twice and ordered spokes that were too long, as a result. Buy the rim first and measure it yourself.

It's tricky to measure with a metal tape measure because you need 1mm accuracy. I saw this method on another forum. He uses two old spokes, trimmed to the same length, Spin a nipple on each end, flush with the end of the spoke, Insert in opposite holes, and measure the gap.

View attachment 201221

A comment on spokes. Existing hub motors tend to use thick spokes, usually 13G, sometimes 12G. There are arguments from old timer wheel builders that thinner spokes work better, but the hub motors are drilled for 13G. Meanwhile, many rims are drilled for 14G spokes. Spoke makers provide spokes with 13G elbows and 14G ends for this purpose. Sapim makes a good one. Quite a difference in quality between Sapim spokes, and the cheap 50 cent spokes I used to order from China. I ordered spokes from wheelbuilder.com last time.

You want a double wall rim. If your measurements are off, the spokes will protrude past the end of the nipple, but the error is inside the rim. With a cheap single wall rim, that's going to stick into your inner tubes, even with thick rim tape. You can be a little long on your spokes with a double wall rim, as you can also add washers,

There's no real skill to buiding a wheel. High school kids paid 5 bucks an hour used to do it, Just be patient, You don't need a fancy rig. I used an old fat tire fork (135mm) clamped to my bench. You can use an upside down bike frame. Tape a piece of paper across the fork next to the rim. Mark the edges with a pencil and true the rim up, In the end, you'll find that a quarter turn on two spokes can move the edge dramatically,

As for the patterns, a single cross is what hub motors use. Keep one wheel intact and refer to it for hints as you do your first wheel. You'll learn that rear wheels are always dished, i.e, the rim is not in the center of the hub. The spoke calculator foresees that. even if you don't know that,

I followed this youtube vid originally,

Credit where credit is due. Bing Thst right there is the kind of answer you hope for.

That’s a good tip about the different gauges. It’s applies.

Here is my project in a nutshell:

I have three hubbmotor wheels from an e-bike conversion kit. Two of them are identical in all but the stamped markings. The one with the bad paint has no markings at all. All three have what appears fo br the same rim, just with two having 26” and the other a 24”.
One of rhr 26” is installed as the front wheel on a tricycle, and I’ve acquired a second tricycle I plan on doing that same with. However, I want to replace the rims with smaller, 20” rims to match the rest of the wheels.
All three hub motors have skinny, road tire type rims that just aren’t suited for the use I need to get from them.
So I gotta replace two of the rims.
I am thinking of using the existing rim from the original front wheel and just lacing it to the motor hub with shorter spikes.
I’ve included pictures of the original 20” front wheel from the tricycle, and the two spare motor hub wheels. The pictures are bad because I had to take them in the dark.
Sorry for the poor quality, but it illustrates what I’m working with.

The goal is to both increase the width to allow a wider tire for better traction purchase and shock absorbsion as well as to reduce the overall diameter of the wheel from the 26” and 24” rims currently installed on the hubs, down to 20”, which is the original diameter of the front and rear wheels.
I will need to purchase at least one 20” rim. Two if the rim in the picture isn’t compatible with either hub. It’s should be. I would think I just need to order shorter, dual gauge spokes.

Right now the plan is to remove the 20” rim from the original front wheel hub, so that I can most accurately measure the ERD using the method you specified, and go from there.
Changing from a 26” and 24” wheel to 20” should provide a notable difference in the torque felt in the seat, I would think. Top speed would will be reduced proportionally.

Thanks again for the excellent information and for taking the time to lend advice. I’m open to any and all input.

 

[gromike]

I built four motor wheels so far, all thanks to Grin's (ebikes.ca) tutorial videos, spoke calculator, and spokes.
The cost of a rim and spokes (and the time) should best be used on a decent motor.
Grin's spokes are reasonably priced, but not shipping, and a custom duty is due.
Regardless, lacing a wheel makes a pleasant winter's eve.
Remember, elbows out, and single cross. 14g/13g single butted spokes. (As per Grin). Though, a direct drive in a 20in wheel would probably be radial laced.