How To Build An Ebike From Scratch: Assembly Day 2

Assembly Day 1 got us a rolling chassis that looks like a bike. If you squint a little. Lets keep up the pace of progress here on Day 2

Introduction
Step 1: Planning
Step 2: Hunting
Step 3: Tinkering
Step 4: Buying
Step 5: Assembling
Build Day 1
Build Day 2 (you are here)
The Wire Harness Tube
Display and Throttle
Chainring
Crankarms
Pedals
Shifter, Chain and Derailleur Install and Adjustment
The Speed Sensor
Battery Attachment
Motor Function Testing
Build Day 3
Step 6: Perfecting
Tools List

The Fight Goes On

Well, really its not a fight. We’re moving forward pretty steadily despite a couple of time sinks that came in the form of a failed Tannus Armour installation, and a ‘peat-and-repeat motor installation where it took a bunch of time to get the cable routing off the motor just right. And speaking of motor cable management, thats where we will start.

We’re nowhere near done with the motor, but on this second day we won’t start there.

Since we bolted the derailleur on the bike as our last act yesterday, lets continue with the drivetrain and start today with…

Craft The Wire Tube

This is a component that is unique to this bike. That doesn’t mean it can only be done on this bike. But its an unusual element for an e-bike, so bear this in mind when you are building yours.

Usually (maybe even ideally) when you build an ebike you choose a frame that has ample room in the forward frame triangle for a battery pack. You secure this battery pack in a battery bag (Since we have already repeated the mantra of DIY does not have to mean half-assed enough for it to sink in, I will ignore the fact that some ‘builders’ use duct tape – or worse – to secure a battery in the triangle). Myself personally I really like battery bags, and I use them on most of my bikes.

Battery bags let you secure the pack on multiple sides, nice and tight. They also let you pad the pack so when you are bouncing around, your pack stays protected. You know what else they do?

They hide all the damn wires.

So, the Apostate’s 1999 Intense Tracer frame has the nearly unique and wonderful characteristic that it fits a Luna Cycle Wolf Pack almost as if it was made specifically for it. Not only was no battery bag needed… I couldn’t use one even if I wanted to. In the lead-up to the actual assembly days, during Tinkering, I tried all sorts of alternatives including different batteries (I have several that can either be pulled out of storage or off of another bike), the use of rectangular, strong cordura/molle bags and even jerry-rigged strapping. No alternative worked.

Its not just a perfect fit. Its the ONLY fit.

So that, as they say, is that. I can forget about having the luxury of a battery bag, where I can stuff all my loose wires and just run them thru slots in the bag, back to front with no one the wiser. I had to come up with an alternative.

For the Stormtrooper, I used matching white heatshrink to cover the exposed wiring, effectively hiding it in plain sight.

I couldn’t do what I did with the Stormtrooper above as the most ‘red’ heatshrink I could find looks pink against the deep, fire engine red of the frame.

Now What?

I decided to make a wiring tube – a bit of fixed plastic pipe clamped to the frame. I can run the main motor harness wire and the unused-but-still-dangly shift sensor wire through it.

I bought a 5-foot length of 1/2″ PEX pipe (inside diameter is actually about 0.68″) from Home Depot for a whopping US$2.93. The ‘hot’ version of PEX is red. But not right red. To fix that I spiral-wrapped the pipe with the red silicone tape I had on hand. I affixed the tube to the frame with a combination of careful wraps of more silicone tape, and red zip ties. Yes I hated to use those ties. Topping off the attachment was about 8″ of velcro cinch straps I chose to use to secure the battery as firmly as possible.

Annoyingly, I did not take close-up pictures of the wire tube during the time it was created and attached to the frame. The tool used to cut the PEX pipe to size was a simple hacksaw and the pipe was cut while holding it by hand. The hacksaw went through it like butter.

Here’s a good, close look at the wire tube at the end of my first ‘live’ ride of the finished bike (note the rain water)

This is another instance where a lot of prep time in advance of the actual build day was spent figuring out exactly how to deal with a problem. While cosmetically I wasn’t thrilled with doing it, functionally it worked very well to both hide the wiring and give it strong protection.

I was never happy with the look of the tape-wrapped PEX pipe, or its connection to the frame.  Shortly after build completion I placed an order for different parts and did a different, better tube.  Since it took weeks for the parts to arrive, many early ride pictures (particularly the ones in the Grand Canyon) show this original PEX pipe.  We'll address its replacement in the Perfecting post.

Run Main Wiring Harness Through Wire Tube

With the wire tube in place, its time to run the wire harness up through it from the motor to the handlebars. Because the connection between the motor side cable and the harness will be in the middle of the tube, and the tube has been affixed to the bike, we need to do this in a particular order.

  1. Feed the harness into the tube from the top, down to the motor. Feed it all the way in until it gets to the knot where the wires separate. This will leave plenty of extra harness wire sticking out, motor-side.
  2. Connect the harness to the motor-side plug. Be careful to line up the little arrows on each plug housing to ensure everything goes together properly. Do this wrong and you can destroy your harness by bending the wire ends inside the plug.
  3. For this build I am not using the shift sensor, which is the wire coming out of the motor with the yellow HIGO/Julet plug. Stuff it into the tube just ahead of the plug you just connected in Step 2.
  4. Feed the harness back up the tube so there is no longer any slack down at the bottom and the wires now feed straight into the tube. Because you stuffed the shift sensor plug in ahead of the wire harness plug, that thick plug, which is almost the width of the inside of the tube, will drag the shift sensor up with it; keeping it safe and snug. When the shift sensor wire has extended fully into the tube you can stop.
  5. You now have a fair bit of extra wire sticking out of the front of the tube. On some bikes, there won’t be a lot of excess. On others there will be a lot. We’ll deal with this on Day 3. Just let it hang for now.
The generic BBSxx wire harness. Green to display, yellow male to throttle, the two yellow females to brake levers. For this project, I am using a harness from California Ebike that substitutes red females for the yellow ones for Magura brakes.
As noted above, most bike builds will not use a wire tube.  If you are using a battery bag, you can just run the harness up inside of and thru the bag.  You can also use velcro onewrap straps or zip ties to run the harness wire along the bicycle frame tubing.  Remember... zip tied cables all over your frame look cheesy.  Avoid them as much as possible, but if you must use them, try to use colored ties that are at least in the ballpark of a match to the frame.  Even a rough color match sticks out a lot less than say black on red.

Attach Display and Throttle To Handlebars

This step is here simply because it has to happen somewhere. This is a good time to get it over with. Attachment of the throttle, by necessity, involves slipping it over one end of the handlebars since its a single piece, tightened to the bars with a small metric hex socket. Displays tend to be a little more flexible, typically using a hinged attachment that makes them a little easier to install. Usually they tighten up with another small metric hex socket. Sometimes you’re unlucky and its a Phillips head.

For both pieces, just get them onto the bars in roughly their expected final position. Tighten them only so they are snug, but still movable. Do not connect them to the wiring harness yet. We won’t put on the grips and brake levers until tomorrow so what we’re doing here really is just ticking a box, so we can do our motor functionality test at the end of the day.

Attach Chainring To Motor

Here again, we’re just taking a relatively easy step that gets us closer to our goal. We need the chainring on so we can put on the chain, which will let us do a motor test.

Since we’re doing a Bafang mid drive motor, attachment of the chainring involves the use of five short M5 socket cap screws. As always I recommend you visit your hardware store and acquire upgraded stainless steel examples. Also – and this is pretty much true everywhere – DO NOT use button head screws. It is tempting to do so because the low profile button heads give a more finished appearance, but they are a bad choice on a bike for a number of reasons – all of which I learned the hard way.

  • A button head uses a smaller hex socket because of its diminutive size. So when torqueing it down (or removing it after time has passed) it is much easier to strip.
  • If a button head is stripped, you will need a specialty tool to back it out. If instead you had used a socket cap, a small vise grip could clamp onto the socket and has a pretty good chance of working.
  • A socket cap is much less likely to strip in the first place thanks to the larger size hex head.
  • A socket cap is rated to withstand more torque (see above).

The prohibition against button heads used to apply especially to M5 brake rotor screws, and after losing a couple of them I switched to M5 button caps, but in recent years, the industry has fixed that problem by using screws with Torx t25 socket heads, which solves the stripping problem. If you can find longer, stainless steel Torx M5-sized screws, those could be an option for fastening the chainring.

The five mounting screw holes for the chainring.

Tighten the chainring screws in an alternating star pattern. The torque spec you use should vary by the kind of screw you are using. Here is a table showing the different common metric screw material grades, and the Nm settings that represent a maximum for each. Keeping in mind we also don’t want to strip out the threads in the socket, I would not exceed 8Nm. The minimum of 7Nm on the chart should also work just fine.

While I am a big fan of never using a thread locker, as a properly torqued bolt doesn’t back off, this is one place where I have violated this rule. However you need to use the right kind of thread locker. Consider Vibra Tite gel. It is a vibration-resistance product with roots in aviation. It never truly dries. It just goops up the threads sufficiently so they don’t back off. I learned about it participating in shooting sports, where the old hands use it on extremely expensive – and delicate – optics that are subject to repeated, severe recoil impact.

If this thread locker is used, bolts will stay put. They can always be backed off with a simple hand tool without risking a seized bolt or a twisted-off socket cap.

Quick Chain Alignment Check

Do this BEFORE applying final torque to the chainring above: Just snug the chainring bolts. At this point, you can now use your final wheel assembly, complete with rear cluster installed, to check your final chain alignment. There is no need to actually install the chain. Just drape it over the chainring, and back over the rear cluster onto its middle ring. How does it look? This is probably the first time you can see for sure what your bike’s chain alignment is really going to be.

For this project, doing this quick check, I found my chain alignment was too far inboard to the frame. My Lekkie 40T ring provides a bit over 20mm of inward offset. Which is a lot as these things go. Too much in this case. I used a Lekkie 2mm spacer (which was included in my motor cover kit) to bring it out just a bit. I also used slightly longer M5 screws to make up for the spacer moving things outboard.

This fits between chainring and motor to move the ring 2mm outboard.

Luckily this simple spacer gave me a best-case solution without having to reinvent any wheels. Which I have had to do in the past.

If your luck isn’t so great when your turn comes, Here’s a link to the likely path to your solution.

Attach the Crankarms

The crankarms are the next logical step after fastening the chainring. Here again we don’t really need them on the bike other than to make some forward progress.

Jump into the time machine again: Drivetrain fully assembled. Note the stainless M5 socket caps bolting the chainring down, courtesy of the local Ace Hardware store.

Crankarms – especially the square-taper variety commonly found on aftermarket ebike motors – must be tightened down by a torque wrench. Torque specs for crankarms specify to a range, typically, of 25-35 ft lbs. Even at the low end, thats tighter than you can guess at.

Especially because you are tightening down onto a tapered spindle (axle), for two reasons. First, the crankarm will slowly tighten down onto the spindle, going deeper and deeper, and you won’t realize it has bottomed out at the right place unless you are monitoring the actual torque being applied. You will be turning and turning on that wrench and watching the crankarm descending down, further and further and think ‘gadzooks thats got to be enough’… It won’t be. If you don’t go too little and tighten too much, you will smoosh your crankarm onto the spindle. The softer aluminum crankarm will spread as its jammed too far down onto the steel, and it will be forever loose (wobbly) once you make that mistake.

Seen from the right and left edges, this square-taper spindle end (from a Cyclone) looks square. The taper isn’t noticeable until you look at the bevel at the corner, head-on.

And of course, if you don’t tighten it enough, its going to come loose sooner rather than later. In fact, square taper crankarms will ALWAYS come loose, and do so faster the more you ride. They have to be maintained. If you are pedaling hard 30 miles a day on a commute, for example, you should check crankarm torque roughly once every two months. If you are riding around the block on a leisurely cruise every week or so, once a year should be fine. But make no mistake: It has to be done or sooner or later your luck is going to run out.

So… thats why you need that torque wrench. This is the first and maybe only time we will use the larger 3/8″ version, because the torque needed is too much for the little 1/4″ unit to handle. Worth mentioning: Its possible to use the larger 1/2″ torque wrench for this job, although its overkill. Still, if you are not down with buying three wrenches, two (the 1/4″ and 1/2″) will suffice.

For square taper spindles and both high end and low end alloy crankarms, I have found a setting of 25 ft lbs (30 tops!) to suffice. I know that Lekkie says 50-60 Nm (37-44 ft lbs) right on the crank extractor plate of the crankarm… I don’t go that hard and I have not suffered any ill effects from being a bit kinder and gentler to my bolts and (expensive!) crankarms. But I also keep on top of my torque settings by checking the bolts regularly.

How do I perform a routine torque Check?

I said this was crucial, and it is. So we’d better go over how to do it, since if done wrong, you will snap off the head of your crank bolt. Don’t ask me how I know this.

Failure is always an option. Could not get the sheared bolt out of this axle, so I had to buy another axle, disassemble the motor and replace it. Use a torque wrench.

If you just set your torque wrench to the desired setting, then stick it in the socket and give it a tug until you hear a click, just the act of doing that imparts added torque to your bolt. So lets say you check it once a day (you won’t) and in so doing you give it that click once a day. A torque wrench either clicks when you reach the required torque or it clicks if you are already past that torque limit when doing a checkup. Yikes. That means once a day if the bolt has not loosened in between checks you are overtightening it a little at a time every time until … snap. Now you are screwed and you will literally have to take an angle grinder and cut your crank arm off to move forward.

The good news is alloy cuts pretty easily with a power tool. Thankfully these were cheap Bafang crankarms and not something a lot more expensive like Lekkie Buzz Bars. Use a torque wrench.

Here’s how you do it right: Back off the bolt a hair. 1/8 of a turn is enough. Now you’ve loosened the bolt just a little, when you tighten it again the click you hear will be the torque wrench for-reals reaching the desired value. If this technique sounds familiar it may be because its used at any decent automotive tire shop, after a pneumatic impact wrench has been used to install your new set of tires.

Attach the Pedals

Again, we are just ticking a box and thankfully this is a pretty simple item. Or… is it?

As an admin and moderator on a couple of online ebike support groups, I literally cannot count the number of times I have seen noobs have a disastrous experience with pedal installation, or catastrophic failure after the fact from a botched installation, where the tragic flaw wasn’t recognized right away. So lets make something simple as complex as possible by looking very closely at it.

One Pedal is Reverse-Threaded

This one item is the cause of almost all pedal installation problems. You would not believe how many people don’t know this, and then cross-thread the pedal in whether it likes it or not. This results in the pedal threading in nice and tight. Until the now-shredded threads give out a month or two later, at which time they see the trashed threads and blame the manufacturer for making crummy parts. Yeah. No. The problem is the loose nut holding the wrench.

Having suffered through so many of these sagas, I was thrilled when in 2019 I bought my Mongoose Envoy and saw it came like this (see pictures below) from the factory. Obviously they’ve seen enough of the same mistake to try and do something about it.

So if you are trying to thread a pedal on and it doesn’t go easily right in… STOP, gather your wits for a moment, think about what you are doing and why the pedal may not be going in like it should, and remember the reverse threading on the non drive side. Then proceed.

You Can Always Tell Which Pedal is Right Or Left

Just by looking at it! You won’t need any stickers. Look at the left picture above and check out the threaded pedal bolts. You can just barely see the left pedal’s threaded portion, but you can see enough. Just above the threads, its ridged. Now look at the right pedal sitting underneath it: No ridges. This is a theme across all pedal manufacturers. Usually what you see is a single circumferential line around the left (non drive side) pedal. Here are the pedals I am using on the Apostate right now. Left on the left picture and right on the right picture.

See that? There is a line scribing the pedal axle on the left, no line on the right. Easy peasy.

Grease The Pedal Threads (Anti-Seize)

I believe I have mentioned what a good idea the use of anti-seize is, and why its especially useful when bonding dissimilar metals like the steel of the pedal and the alloy of the crankarm. Its also particularly helpful if you are going to be connecting and disconnecting a threaded part, as the anti-seize will protect those threads from galling while they are being screwed and unscrewed repeatedly over time.

Why would you be taking the pedals off? Well, on a bicycle that is going to be stuffed into the back of a car, the pedals stick straight out on both sides. Also thanks to the rippy, stabby little studs festooned across most mtb pedals, they are going to hang up on and tear into all sorts of things. Just taking the damn pedals off makes the bike amazingly easy to manipulate and move around inside of a car.

Good luck leaving the pedals on and packing a bike in with all that soft cloth and canvas to rip into.

Can it be done with the pedals on? Sure. Can it be done as easily after taking 30 seconds to remove the pedals? You know the answer 🙂 .

Use Very Light Torque When Tightening Pedals

This goes hand in hand with ease of removal, but the benefits of doing this are not limited to a bike that has its pedals frequently removed. To the contrary, this is how you should install any pedal on any bike.

And no, this is not the advice you are going to get from most everyone else, everywhere else. I’ll make my case:

Its common to see torque specifications for a bicycle pedal in the ballpark of 40 Nm. Thats pretty tight. I never do this. Instead I use a pedal wrench and just give a quick, light tug to snug the pedal on when it bottoms out in the crankarm.

Unless someone helps them come undone, pedals will not work their way loose through normal use. That is why the left pedal is reverse threaded. In fact, the threading on each pedal, coupled to forward pedaling action, means pedals self-tighten as the rider rides (assuming the pedal bearings are functioning, but that is a rabbit hole we don’t need to go down; especially given the modern use of sealed bearings).

Given that pedals in good working order, used properly, cannot loosen: there’s no mechanical reason I have ever come across to use high torque on a pedal. On the other hand, I have repeatedly been thankful my pedals come off easily when I want them to – and only when I want them to – as a part of the routine maintenance, transport and wear/tear of a stable full of bicycles over many years.


So thread them on, put the right pedal on the right side, just give a quick tug on them after they are threaded on and fuggedaboudit.

Install Shifter, Chain and Adjust Derailleur

I have used the Box Two derailleur and single-shifter in the past. Since I am using a Box Two derailleur here, I decided to upgrade to the Box One single-shifter, with a matching Box One shifter cable kit. The Box Two shifter worked great, but the upgrade is not much more money and has a marginally better handlebar clamp. So I splurged.

Installing a shifter involves some standard jobs. I’ll cover those in brief and then note how this bike, because of how old it is, needed some special handling.

Unbox The Shifter

I find that I don’t have a picture of the actual Box 1 shifter I put on this bike, so I swiped a couple from the store page at Box Components where you can buy one for yourself (I got mine at Jenson USA).

Looking at this shifter above, the most noteworthy thing to be aware of as a new bike builder is the fact this shifter has a hinged attachment ring. That means you don’t have to pull off (or cut off as is often the case) the grips on your handlebars, should at some point in the future you need to remove the shifter, reposition it… whatever. That silly little feature – that seemingly has nothing to do with the intended functionality of a shifter – is a big deal over the life of the bike.

Box Components does not deliver the shifter as shown in the picture above. What you get is like what you see in this different shifter, below:

Put simply: you are given a shifter with the shifter cable already installed. this is a nice little timesaver I have come to expect from every shifter I have ever bought. They all seem to come with the cable. Thats great, but you need more than that. Here is a complete parts list for a plain vanilla shifter cable; completely installed from the shifter on the handlebars to the end of the cable sticking out of the derailleur:

  1. A cable ferrule stuck onto the end of
  2. The shifter cable housing, which goes over the shifter cable and all the way back to the derailleur and terminates in
  3. Another cable ferrule. The ferrule snicks into a slot made just for it on the derailleur, where the cable continues on into its clamp, and is terminated by
  4. A cable end crimp

While I have all of these parts in quantity in little cubbys in my workshop, I decided to buy the Box One Shift Cable and Housing Kit. Box’s marketing people put up some snazzy graphs showing how muck slickerier their cable housing is versus The Other Leading Brand. So… fine. In for a penny, in for a pound. I spent the $25 on a dedicated parts kit that gives me everything I need for how I intend to build this bike. You’ll see why I put that in italics further down the page.

Now that we’ve established the parts in order of assembly above, your first job to install your shifter assembly is to bolt that shifter loosely onto your handlebars. It goes on the right hand side unless you fancy yourself some kind of rebel and want to put it on the left. Upside down and backwards. Either side, at this point the shifter and its bare cable should be just barely be able to hold its position on the bars. Not so tight it will leave a mark if you move it around.

Whats a Ferrule?

Its a metal or plastic finishing sleeve that covers the end of your bare, cut shifter cable housing.

Above: The little whatsit sitting next to the bare cable is a ferrule, which I then stuff onto the end of the shifter cable housing. The fit will be snug but easy to make just by hand. No tools necessary. We are not going to attach the ferrule on the other side just yet.

Once we have fit the ferrule onto the end of the cable housing, we want to run the wire coming out of the shifter thru the housing. All the way through. The shifter cable will be longer than the shifter housing and we want it that way. Snug up the cable to the just-snug-on-the-handlebars shifter.

Now that we have the cable-and-housing hanging loose and on the ground, we want to run it back to the derailleur along the bike in the path its going to take when its finally installed. There are a variety of ways you can do this, but perhaps the easiest is to use cheap, reusable velcro OneWrap cable ties. I love these things, and they are perfect for this job as they are reusable, easy on/easy off and not permanent – unless you want them to be at which point they seem to last forever on a bike.

Important:
When running the cable back to the derailleur for this fitment exercise, leave slack up front coming out of the shifter so the cable is never tugged upon no matter what position the handlebars are turned to.

You should be able to figure out the path the shifter cable is supposed to take as there will be braze-on cable guides along the frame dictating the appropriate path. Most modern frames will have what looks like a little altar that you lay the cable across. Under the altar there is a slot made to run a little clip or a zip tie through to … strap the cable down… er… onto the altar (I should have sounded this out in my head first before coming up with that name).

Most modern frames have these simple cable mounts where you just lay the cable over it and use one zip tie (or two very small ones) to clamp it down.

I am bringing up this ‘altar’ and ‘modern frame’ business because my frame, designed in the previous century, is a product of an era when such things didn’t exist. So I had to improvise. But, I digress. We’ll get to the improvisation part last. For now I want you to see what it is that most likely you will be looking at on your own frame.

So you have followed the path laid out by your frame’s braze-ons to route your cable, and strapped it down temporarily with wire ties or similar. What you have now is a cable and guide assembly that is hanging out past your derailleur and is way too long for it. Its time to cut the cable to size.

Top Tip: Don't screw this up.  Its better to cut a little too long than it is to cut too short.  You can cut again if its too long.  Too short... not so much. 

Hold the cable with your hand such that it loops up and goes directly into the socket on the derailleur that is meant to accept it. You want the cable to go in straight, but not have so much extra in the loop it will catch on something – when you are whizzing down a hill a branch could tear that cable clean off, or worse.

I am measuring the cable to go right into the little hole where that arrow is pointing.

Find a way to mark the spot you’ve chosen. Do not cut!

Why? Because the cable is still inside the housing. After marking the cable, you need to get some slack up front at the shifter and pull that cable entirely out of the housing. I know you only really need to pull it back several inches, but lets not guess wrong and screw up. Another 10 seconds of effort and the cable is safely, completely removed.

NOW you can take your cable cutters and, with one quick authoritative snip, cut the cable housing to size. Run the cable back thru the now-snipped housing. And here we are:

Snipped housing and still a full-length cable.

Now that the cable has been threaded back thru the housing and pulled gently taut, we fit the second finishing ferrule over the bare wire, and snug it down onto the end of our cable housing.

Next, pull the wire through the receiving socket on the derailleur and gently pull the cable housing assembly into that socket so the cable is snug inside of it. You aren’t trying to clamp anything down at this point so I am using words like ‘gentle’ on purpose.

Turn all of your ‘provisional’ and ‘temporary’ cable mounting into permanent mounts. If you do it right, ‘permanent’ is a misnomer as all you will have to do is cut the zip ties to free your cabling up again. But for our next step, we want everything in place as it is going to be as a final assembly. Try and get your positioned shifter about right on the handlebars. This will be one place where having a little extra slack in the fitment will help you later on down the road.


At this point I’m going to jump from written description to video. We’ve covered the installation of a new cable and a new cable housing. From here I can let the Box Components installation video do all the heavy lifting for final cable attachment, chain sizing, chain installation and finally derailleur adjustment. These instructions work great for the entire rest of the process, and not just for a Box Components drivetrain. Remember if something confuses you, you can always hit pause, drag back the cursor and play a step over again until you understand it.

Some quick notes on the video above:

When I first saw the instructions on derailleur adjustment in this video, I was skeptical. I was very familiar with the method shown in the excellent – and gold standard – Park Tool video below. However, what Box is describing above is a lot simpler than the method Park lays out… and it is after all the manufacturer’s official installation instructions. So I followed the instructions and was entirely surprised they worked perfectly.

The chain sizing method shown is different than many other instructions on chain length. Nonetheless it is absolutely correct for a 1x (single front chainring) drivetrain. Many builders get this wrong in part because there is so much misinformation on how to size a chain; particularly on a 1x system.

Here’s another source that describes the same method. This time in writing:
Installing A New Chain For Your 1X Drivetrain (How to do it Right!)

The key is to only slightly tension the rear derailleur cage. That ensures you have a taut chain, but also that there is much chain on your bike as your derailleur cage can possibly wrap. Make it any longer and it will sag and skip. Any shorter and you have shortchanged yourself when moving up to your biggest, lowest gear.


If you have followed through step by step on the video above, you have now installed and adjusted your your drivetrain. However, if shifting isn’t perfect, here are a couple of alternatives.

A Different Example

I recently installed a low cost Microshift Advent system on my Mongoose Envoy. The Microshift install video shows an entirely different derailleur adjustment procedure. And since the Box video worked so well when I first used it (on 2Fat), I decided to follow the Microshift directions to see what happened. It worked. This video has a slower pace and gives a much better look at some of the components and operations common to all 1x drivetrains (like the limit screws). However, I would not follow their directions on cutting/sizing the chain, as the method shown in the Box video addresses the real issue that has to be addressed (chain cannot be too long, so you make it as long as possible).

The Park Tool ‘Gold Standard’ Tutorial

This is the method I have used for years. It takes the most time, but it always works, and if you do nothing else, just watch it and learn all about how your derailleur’s adjustors interact. The methods above worked great, but they may not translate to your derailleur. If so, do it the long way with these detailed adjustment instructions. Since this is not an installation video it concerns itself solely with adjusting a derailleur in a completely installed drivetrain. This video is also the best in terms of helpful visual instruction of common component parts.

Unique Weirdness Worth Mentioning

My chosen frame comes from a bygone era. In that era, cable routing was done differently. First of all, those handy little zip-tie altars hadn’t been conceived yet. Instead on this frame we have circular braze-ons that require the cable to be routed inside of them. Want to re-route the rear brake cable? You have to disassemble the brakes to make that happen. Which was a pain back then, but more so now that we have hydraulic brakes that you don’t just take apart unless you feel like bleeding the system all over again.

It gets worse with the shift cables. Here again on this vintage frame we have the fixed cups meant to accept a cable end… but back in the day, cable housings were nowhere near as well-engineered (and slick) as they are today. So you see a frame designed to only use a minimal amount of cable housing wherever there is a bend, and then run all straight lengths of shifter or brake cable bare and out in the open air.

Well its not 1999 any more. In 2022 we have some pretty slick cable housings, and in fact my Box 1 shifter kit’s main purpose in life is to provide super slick performance with resistance so light the Box Components marketing department went crazy making sure you know all about it. On top of that, the brake cable runs meant for wired cable aren’t going to get any since we are using hydraulic hose instead.

Luckily there are inexpensive little doodads made that let you convert – more or less – these old school fittings to accept hose. Here they are installed, prior to cable and hose installation.

And below, here is how they are used. Not ideal, but a necessary evil unless I wanted to compromise performance for a vintage look on the shifter cable (which I didn’t) You can find these little parts (listed as ‘cable guides’) on the parts list in the Planning post.

And you will not need to use them at all if you are building your bike with a frame manufactured in the modern era.

Yes we’ll trim that zip tie. And I think this is the only picture of the battery mount on the bike, before I permanently attached the battery.

Figure Out Placement and Install The Speed Sensor

I’ll make no bones about it: This item was very time consuming And there’s no reason it should have been. In the end I used almost exactly the same approach as I have taken with all of my other bikes, and the final solution looks like something I could have knocked out in a half hour. Sometimes when you are building a bike these things just happen. I only bring this up because I want to emphasize that if something similar occurs in your build… don’t get frustrated or upset about it. Just stick to it – or maybe walk away for the afternoon and come back tomorrow, fresh-faced. It’ll work out.

Like this one did. Here it is fully installed and wired up:

At left, you can see an overview of the entire sensor assembly including the magnet on the wheel, attached to the spoke. Please note this is not the Bafang magnet that came with the sensor kit. The Cateye sensor magnets you can buy from Amazon are lighter weight, and at least as strong if not more so.

As you can see in the photos above, the sensor is not sitting directly on the stay. Its sort of strapped to something. That something is a marine cable crimp. A couple of them are pictured below, and while they are not quite the same as the one I used on this project, the picture gives you an excellent idea of what they look like. I buy them at my local hardware store, but you can find them on Amazon too.

I have used crimps like this for most of my BBSHD builds. They are square-ish enough and rounded enough that they can easily be mounted either on a round surface or as here: a square one. They have rounded edges that mimic a rounded chainstay, which the Bafang sensor mount is curved to and designed for. And of course being a hunk of hollow aluminum, they are both strong and light. Below is perhaps my first use of a cable crimp (I was still using the Bafang magnet back then. This photo was taken in 2018).

In both cases as shown above, the cable crimp was used to move the sensor inward, closer to the spokes. If I hadn’t done that on either of these bike builds, the sensor would be nowhere near close enough to that magnet to register.

Here is an up close look at the entire Bafang speed sensor kit. the wire that goes to it comes directly off the motor and is included with same.

Also above is a close look at all the parts that make up the speed sensor. The silver screw goes into the back side of the magnet to glom it onto a spoke. The black screw is a set screw. The actual sensor end is a sliding arm that you can move inward or outward to help you come up with a fitment that works on your bike. This set screw anchors the parts once you’ve decided what position they need to be in. You can also see the two slots on the sensor base that you will thread a couple of zip ties thru to do your final anchoring. On the other side of those slots is an adhesive-backed curved surface that we’ll use as described below.

Lets go step by step on how this mounting is accomplished:

  1. Figure out placement before sticking anything onto anything else. Your speed sensor will need to pass within about 1/4″ of the magnet (see the installed pic above – the middle of the three. That is how close you want to get). You can get away with a little more separation if you use the stronger Cateye magnet seen in this project. But don’t push it if you can at all help it.
  2. Lay down a bit of 3M 2229 mastic rubber tape directly onto the chainstay. Just big enough for the crimp to smoosh into, which is what you will do next. This will provide a vibration free base for the crimp, as well as protect the paint on your frame.
  3. Wrap the crimp with your paint-matched silicone tape. You can see in both pics above I used white. I actually have some gray now that I will use if I ever have to remove and replace this working mount (if it ain’t broke…). Between the tightly wound tape and the sticky, thick mastic, you have pretty much locked that crimp onto your frame.
  4. Attach the speed sensor’s curved base to the curved corner of the crimp. This is where the shape of the boat crimp really shines as it mates the sensor perfectly to what is now a solid mount. The speed sensor has an adhesive base. Peel off the protective film and carefully stick the sensor onto the crimp. It should now stay put, but that sticky base cannot be relied on for long. Which is why our next step is to…
  5. Zip tie the sensor to the mount and chainstay. For the Apostate, you can see I used grey zip ties to make as close of a color match to the bare alloy as possible. For the white bike above (that is the Stormtrooper in case you were wondering) I used translucent white zip ties. Once those zip ties are on, you have a rock solid mount whose only weakness is the plastic of the sensor. Be careful when you remove a wheel (on some bikes its smart to deflate the tire. You’ll know after the first try at taking the wheel off).

Connect Display and Speed Sensor

Coming out of your motor is a plug with a captured knurl-nut on it. That is your speed sensor cable. It has a flat side on its otherwise circular surface that matches up to the speed sensor. Plug it in and thread that knurl nut onto the threaded sensor, so the connection is locked together nice and tight.

Attach The Battery

Ordinarily I would not be placing the battery in the bike in its final position at this point. I’d usually put it on a table next to the bike stand; perhaps connected by an extension cable for convenience. This bike was different as I expected the battery to be a permanent fixture on the bike. I needed to be able to see the wiring challenges ahead of me: all of that wiring was going to have to live in plain sight. Cable management was not just something cosmetic I could tidy up later when I felt like it on this build.

Mount Fitment

As noted earlier, I found – via a V1.0 pack I already owned – the Luna Wolf pack was a perfect fit for this frame. I had a spare V2.0 magnet mount I wasn’t using, and that is what you see in my early fitment pictures with the bare frame. Here’s a closeup of that magnet mount.

Thats a lotta magnets!

Its a really well-thought-out product, what with its variety of mount holes and lonnnnng magnet engagement. On a frame with a big triangle you won’t be moving that pack without really wanting to, which is a good thing. On the Apostate, fitting it in the space available was tough, but once that pack clomps onto that magnet it really is best to not try to move it at all (and yes, it did eat one of my fingers once when I wasn’t careful).

To be brief, I bolted the magnet mount as centered as I could in between the two bottle bosses on the frame. The idea was, the attachment is so strong I did not want to create a situation where the battery being pulled up bends a long extension of magnet mount. These two pieces really, really do not want to separate and damaging the frame or the mount is a real possibility (my bottle bosses are drilled steel inserts into the alloy frame… 1999 technology).

As with some other elements of this build, this mounting issue was unique to this specific frame. Your experience is much more likely to be simpler and less drama-filled. This magnet mount is not problematic on modern frame construction.

Battery Placement

I wanted this puppy pushed as far forward as possible. For starters, once this pack is on its on. Its not moving and I need to be able to connect and disconnect my cables to and from this otherwise wireless battery pack (a unique feature of the Luna Wolf – you make your own cables and plug them into the battery using built-in XT60 and XT90 receptacles).

Speaking of which, when building an ebike you are going to need to be making a cable or two. This is a great time to introduce you to a complete tutorial on the subject:

How To: Safe, Reliable Electrical Crimp Connections

Since I didn’t do the wires on Day Two, we’ll save that discussion for Day 3. Suffice it to say as Day 2 wound down, I just made a test connection to the motor from the battery with a short Anderson-to-XT90 adapter (BBSHDs from the factory have a long battery lead terminated with Anderson powerpole connectors).

Test Motor Functionality

Its getting late, and I’m starting to get sick of looking at this bike. I need to knock off for the day. But before I close up shop I want to just test the motor to make sure it works. Otherwise I’ll be tossing and turning in bed, wondering if I got it all right. With the speed sensor and battery connected, all I need to do to make a functioning motor is to

Connect the Display

Remember how early in the day we put the display on the bars, and left the connection wire dangling? Its got a green HIGO female plug on it and the only place for that to go is the green male HIGO plug on the wire harness that we also left dangling nearby. HIGO plugs have little arrows on each side that you line up (also there are pins on the inside you need to see to double-check you have it right). Push them together once you have them lined up. These waterproof connectors will often come together with a little, audible pop.

Connect The Throttle

When we put the display on the bars, we also put the throttle on. Now its time to reach for the female yellow plug on it, and mate it to the male yellow one on the wiring harness which is the only possible match. Same deal here: Match up the arrows, and double-check by also visually watching the inside pin on the male side line up with its matching slot on the female side.

Turn On The Display

This is it. Moment Of Truth time. At this point, if you hit the On switch the display should light up (naturally you need to have at least some juice in the battery 😀 ).

When I did it for this bike, it worked! Now what do I do? Well the bike is up in a stand, so its safe to give it a little throttle… and the wheel spins around! Yay throttle works! What about pedal assist? Click down to the minimum level of assist (“1”). Grab the wheel to stop it from spinning (since we haven’t put the brakes on yet) and now… rotate the pedals. If the motor fires up and spins the wheel again, our pedal assist sensor works! Look at the speedometer display. Is it registering some kind of speed value? If so, the speed sensor is working. Look at the back end of that sensor. There’s a little red light you probably didn’t notice before. Is it lit up? Hooray. So far so good.

And with that, its time to call it a day.

End of Day 2! Its almost rideable. Almost.
Final Day 2 Note:
You may have noticed the chain is not installed in the end-of-day picture above.  On the actual build day, chain installation and derailleur adjustment was held over to the start of Day 3.  I spent so much time fighting with unusual issues getting the speed sensor positioned I lost a lot of time.  By the time the photo above was taken it was evening.  I was done looking at this thing for the day.  A less fiddly build (i.e. almost all of them) would have allowed for chain attachment on Day 2.

We’ll Be Done Tomorrow

Author: m@Robertson

I'm responsible for the day-to-day operations at my place of business: Leland-West Insurance Brokers, Inc. We do classic and exotic car insurance all across these United States. I'm also an avid auto enthusiast, a born again cyclist (i.e. an ebiker) and participate in medium and long range CMP and NRA sanctioned rifle competitions.

11 thoughts on “How To Build An Ebike From Scratch: Assembly Day 2”

  1. Extremely detailed article. Thank you very much for all of this valuable information. Cheers.

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