RAT Electric Bikes

You now have a ‘donor’ bicycle, a rear-hub kit, and a battery with mounting hardware. What’s next? Taking inventory, that’s next. What parts on the bicycle can be salvaged and what can’t? Using my ‘budget’ Trek 4500 as an example NOTHING WAS SALVAGABLE! Here’s my inventory list and parts cost. If you’re able to get a bike with more salvage value, then just subtract from the list below the things you DON’T need to buy, and that will be a fair estimate of your build cost. Case in point, the parts list below add up to just over $600, and that’s AFTER you just put out $600 for the e-bike kit! Are you sure you want to do this? You can stop now and buy that RadCity 4 for $1600 and be done with it. Sounds tempting…

rear derailleur	$22.25
front derailleur	$18.00
chain	$15.15
shifter set	$17.54
tubes	$15.89
pedals	$14.83
seat post	$16.95
seat	$19.07
head bearing set	$17.88
crank bearing set	$28.29
wheel (for disc brake)	$79.48
rim strip	$9.57
disc brake set	$55.10
handlebar	$20.34
handlebar stem	$21.18
headset spacer set	$7.41
cable set w/ tool	$17.69
front fork	$104.03
tires	$50.00
controller case	$20.00
crank set	$30.00
handlebar grips	$7.00

Even though I tried to capture all the major build expenses, add another 10% for other stuff like a bell, lights, mirror, cell phone mount, thumb throttle mod – that sort of thing.

I didn’t say this build would be cheap, but there are ways to control your final cost. For example, my next (mid-drive) build will not be using disc brakes. I like the brakes and wheels that bike has, so other than the mid-drive kit cost, my other rehab expenses should be minimal…

Without getting into a rear-hub versus mid-drive debate for the moment, I’m just going to focus on rear-drive kits. My experience so far is with a rear-hub system sold under the name ‘Voilamart’. I learned about Voilamart through some YouTube videos and thought it would be a good place to start. Here’s the kit I used for my first build (and should have bought for my second build):

Voilamart Electric Bicycle Kit 26″ Rear Wheel 48V 1000W E-Bike Conversion Kit with Controller and LCD Display ($290 on Amazon)

The other expensive component you’ll need to get your e-bike on the road is a compatible battery. The one I chose, and am very happy with so far, is the Joyisi 48v 14ah battery

48V 14.5AH A Grade Cell (200W-1000W) ($310 on Amazon)

There are many other rear-hub systems you might want to consider. Bafang makes a nice 48 volt 500 watt kit for several different wheel sizes (here). Again, my experience (so far) is with the Voilamart rear-hub units, but you’ll find many of the commercial e-bike builders use Bafang parts, so I expect Bafang’s reliability is quite high considering that these builders need to stand behind their product.

PS – Later on, I’ll talk about mid-drive options, but until I install my Bafang mid-drive kit, I just don’t have enough experience yet to share. Stay tuned…

So, you have your bicycle and you’re ready to get started. Of course you’re going to need to think about e-bike DIY kits, but first, invest in some essential tools. Here are most of tools I use:

From left to right;

Star nut setting tool

Bottom bracket extractor

Cable cutter

Crank puller

Bicycle tire levers – 3 work, 4’s better

Crescent wrench and assorted open-end/box wrenches

Screw drivers

Chain breaker

Assorted Allen keys

Assorted sockets, socket wrench

(Optional) Headset press-in tool (I had a bicycle shop do the bearing race extraction, but made this $8 press-in tool to insert the new races)

(Optional) Lockring Removal Wrench & Chain Whip with Cassette/Bicycle Flywheel/Sprocket Remover

(Optional) Bicycle Chain Master Link Pliers Tool for Quick Link Removal

And of course, surgical gloves to keep your hands from getting grimy.

I’m sure there are a few other tools I forgot. And for my builds, a soldering iron, lead solder, electrical tape, assorted Zip ties, drill and drill bits, vice grips, etc. also have a role to play.

Bottom line: I helps to have a fairly well stocked workshop when building e-bikes! Also, even though I don’t own a bike stand, I do use a hoist system to elevate the bike when I’m working on different parts or tuning the derailleurs. This is very handy…

Being a Gary Fisher and Trek brand fan, my search is a bit easier than most, but let me reiterate what’s most important when considering using your existing bike or purchasing a used bike for your e-bike build.

1. Look for sufficient space between the horizontal (top) and down (between the headtube and bottom bracket) tubes for your battery. And while you’re here, it’s a good idea to know the bicycle size (measured from the center of the crank axle to the top of the seat tube) so you know the frame’s not too short or tall for you.
2. Look for usable/reusable components. The better the bike’s condition, it makes sense that your build should cost less to complete. Also, be sure you’re buying a bike that you e-bike kit will work with. My builds have all been on bikes with 26″ wheels. Be sure your kit matches the specs of the bike you’re going to use.
3. Consider what upgrades you’ll want to invest in and how much that will cost above the bike’s purchase price. On the average, your e-bike kit will add 20 lbs or more to the overall weight of the bicycle. Add your weight, and consider that you might be riding at speeds slightly higher than you would without a motor, and now you might need to think about installing better brakes. I prefer disc brakes on my builds, so I make sure the bike either has disc brakes installed, OR has the fork and frame hardware that makes a conversion to disc brakes possible.
4. Once you have made your bicycle choice and have a rough idea what you want to do and how much it’s going to set you back, it’s time to start preparing for your build. Next, I’m going to talk about some tools you’ll definitely want to invest in to help make your e-bike dream come true.

PS – I just went through the exercise of locating a suitable e-bike on Facebook Marketplace (my favorite place to shop for used bicycles). Here’s what I found (date 1/9/2022) for example:

Mens Trek 820 26″ Mountain bike 21 speed 19.5″ ($125)

I spent about this much just for a replacement front fork for my 4500 build, so at this price point, this could be a good platform to start with if the frame is straight and the bike has been taken care of. I would definitely check this bike out if I was in the market for another rear-hub build…

Whether you intended to or not, you just connected with my new website which speaks to DIY (do it yourself) electronic bicycle builders everywhere. In the ‘About’ section of this site, I’ll explain what this is ‘all about’, but for the moment, Welcome! I’m glad you’re here and I hope you’ll be able to learn something new before leaving to go to the site you had originally planned on visiting. Thanks again, and bye for now…