Complete noobie asking about converting a bike

[dudebro]

Hello! I'm an active mountain biker with many years of experience in XC, trail, enduro and downhill riding. Last weekend I got to borrow a high end Specialized e-bike for test ride. I certainly could see the the benefits but I still did not get convinced. Because of the assist works only when pedaling and the 25 km/h speed limit, the bike did not feel that mind-blowing.

So I started wondering about building a custom e-bike and found this forum. Is converting an existing ebike really a reasonable project? I'm planning to use the bike 100 % for mountain biking, zero commuting, single track and off-road only. Are there mid drive conversion motors that are really robust and can whitstand hard enduro/downhill style riding? I am pretty confident I can come up with a solution to securely attach battery cells to the frame. If the project itself is worth starting

I read this topic:

eMTB - Specialized Enduro with CYC Stealth (aka The e-Duro!)

Hey all, figured I'd post this most recent build up for interest. Not quite a build thread as I've finished it for the most part, but it's interesting to me and maybe other folks are interested. Here she is on her first ride this past weekend: Goals of this build: A real, real, electric...

endless-sphere.com

and became heavily inspired. My knowledge of aftermarket mid drive conversion kits are basically zero. I know Bafang and CYC make motors but that is it. What kind of motor should I choose if I want to have plenty of power and a possibility to use the assist without pedaling? Basically I want a bike that I can ride as ahard as a downhill bike is intended and it should have noticeable more power than a normal 250 W ebike that assists only when pedaled.

I have a good long travel bike already that I could convert. Another option would also be that I get an used e-mtb, remove the stock shimano/bosch motor, and install something more powerfull. Is there more powerful aftermarket motors that could replace fr example a regular Shimano EP8 motor?

Thank you in advance!

 

[2old]

You'll get lots of advice here, maybe some contradictory, but a Bafang BBS02 (or the slightly heavier and more powerful BBSHD) and CYC (at about twice the price) are excellent systems. Both have PAS (pedal assist) and throttles AFAIK (I've never built a CYC). My BBS02 has been perfect for seven years. The most critical thing to look out for in a donor bike IMO is that the bottom bracket area does not have a flat spot like many current ones or the motor will hang down like a cow's udder. Start reading and ask questions.

 

[Chalo]

Are there mid drive conversion motors that are really robust and can whitstand hard enduro/downhill style riding?

Unless you pick a known crappy option like TSDZ2, the mid drive will be just fine. The thing you have to worry about is the drive components. The more power you stuff through them, the smaller a chainring you use, the more wear and breakage you'll see in the chain and sprockets. Know this, and either use cheap and robust parts like Microshift Acolyte, or else resign yourself to spending a pile of dough keeping your bike in working order. It sounds like you're the kind of rider who loads the bike onto a smog machine and carries it to a playground to ride, so I guess financial responsibility probably isn't your jam. But be aware of the costs.

Me, I'd use a BBS02 with a 42t chainring (stock, Lekkie, or Luna), Acolyte 12-46 cassette and 8sp shifter, and an e-bike rated chain. At 48V and 25A, you'll have plenty of power for climbing and for top speed in excess of 30 mph. And I'd keep spare chains, cassettes, and chainrings handy.

 

[scianiac]

The main thing I think you should think about is how you will be using it, if you are using primarily with a throttle then a BBS-HD/02 would be fine and only downside is loss of a little ground clearance which depends totally on what your trails look like. If you want to use it in pedal assist then something with a torque sensor like the CYC drives is pretty critical for mountain bike use, you need that precision power control that you don't get from PAS for any technical riding. The main downside I would say of the CYC besides cost is they can be a little noisy, not terrible but louder than most other options and louder than factory ebikes.

 

[dudebro]

Thank you for the replies! I think the opinions from more experienced converters really help with my thinking process. I'm aware that the drivetrain components absolutely will wear out quicker with powerful motor than without any motor at all. I was planning to go with maybe 10 or 11 speed drivetrain, so the parts will be cheaper to replace. I'm also interested in the new Shimano linklide rear cassette, if Shimano estimates right, the 300 % increased durability sounds good for an application like this.

My frame is a Canyon torque that slopes slightly upwards from BB so I think I would not be sacrificing too much ground clearance with mid drive conversion. I have already replaced the fork and front wheel with 29er versions so there is more ground clearence than in the stock version. Pic is not my bike, but an example where the shape of the bb area can be seen:




>The main thing I think you should think about is how you will be using it
I think I would be using both, throttle mode and pedal assist mode. I'd like to keep the pedal assist option open so I can attend group rides and ride with my friends. But when riding solo I'd like to have throttle and ability to use more power than Shimano/Bosch e-bike motors. So maybe the CYC would suit my needs better.



And another thing is the batteries. I think I can come up with a secure and clean looking solution to fit batteries to the bike. Only thing is that because it is over 10 years from high school, I remember barely anything from basics of electricity. I'm assuming it would be wise to use 1860 battery cells, but how many of them? Usually ebike battery capacities are arvertised in Wh. Quick googling tells me that 1860 cells are 3,6 V and 3500 mAh so if I recall correctly one 1860 cell should be 12,6 Wh, correct? If I used 40 pieces of 3500 mAh batteries, the capacity would be 504 Wh.

The bike I tested earlier had Shimano EP8 motor with 504 Wh battery. It barely gave me 30 km of trail riding with the trail assist mode. So I assume I should double the battery capacity on this project if I want the bike to be usable in real life.

 

[offGridDownUnder]

Lithium cells tend to catch fire and explode if

• overcharged
• charged at too fast a rate
• physically smacked around
• overheated

Fires sparked by lithium batteries are confounding firefighters
There are many more stories about this as it is happening more due to more EVs. Using an EV is fine. Mis-using an EV has serious consequences.

• Buy quality name-brand cells only. Ask the people here.
• Size the pack large enough that you can use it without using the entire charge each cycle - 20% charged to 85% charged avoids overcharging. The Grin Satiator charger can do this automatically.
• Never leave a pack on the charger while you are asleep - the gases will get you before you wake up.
• You cannot pick up a burning Lithium battery and throw it outside - even if it is attached to your bike and you try to grab your bike frame - you probably won't be able to get close without serious injury.
• Water does not put out a Lithium battery fire.

Consider buying a quality pack from a reputable maker who guarantees to use quality cells.

 

[dudebro]

Lithium cells tend to catch fire and explode if

• overcharged
• charged at too fast a rate
• physically smacked around
• overheated

Fires sparked by lithium batteries are confounding firefighters
There are many more stories about this as it is happening more due to more EVs. Using an EV is fine. Mis-using an EV has serious consequences.

• Buy quality name-brand cells only. Ask the people here.
• Size the pack large enough that you can use it without using the entire charge each cycle - 20% charged to 85% charged avoids overcharging. The Grin Satiator charger can do this automatically.
• Never leave a pack on the charger while you are asleep - the gases will get you before you wake up.
• You cannot pick up a burning Lithium battery and throw it outside - even if it is attached to your bike and you try to grab your bike frame - you probably won't be able to get close without serious injury.
• Water does not put out a Lithium battery fire.

Consider buying a quality pack from a reputable maker who guarantees to use quality cells.

Good info, thanks! What battery pack makers are the good quality ones? I live in Europe if that makes recommending things easier

 

[offGridDownUnder]

Good info, thanks! What battery pack makers are the good quality ones? I live in Europe if that makes recommending things easier

Alas, I am in Australia. I would post (and search) a separate topic so people can see it if it's not already answered. It is a different question.
Cap Rouge here in Victoria has good batteries. I think they may have their mother company in the Netherlands.
The Satiator is from Grin Technologies in British Colombia, Canada. It may be supplied by local companies - search for that.

 

[2old]

em3ev for your battery. Also, consider using 8-speed for components (unless you need to wear out the ones on your bike first). You'd be surprised how few gears you need with a motor; I ran 11-17-28 on my BBS02 spaced 8-speed with Altus shifter and derailleur in its first iteration and it was durable off road.

 

[scianiac]

The battery can be the annoying part on these full-sus bikes due to mounting so I'll share my experience with batteries on mountain bikes. The first thing is to consider just how much battery you need, some of these production ebikes come with frankly unnecessarily large batteries to counteract buyer range anxiety I guess? You probably know how long your average rides are and it's not exact math but you can assume that in pedal assist it will be pretty close power usage to a factory ebike and in throttle it depends a lot on the terrain but maybe 2-3 times the consumption if using it pretty aggressively.

My primarily pedal assist ebike has a 270wh pack and I've never gotten close to using it up in pedal assist but have a couple of times when using the throttle. If I recall about 3 moving hours in pedal assist and I wasn't even close to empty, about 2 in mostly throttle but it's pretty low powered. My throttle only bike I'm building a 600wh pack and I can't see how I will ever use it all.

For mounting without doing a custom battery that is shaped to fit it will be pretty hard to mount anything but a smaller pack. My solution on the throttle only bike is lipo bricks so that I can mount them in multiple locations but I do have much less space than you have. The pedal assist bike I still run with a backpack battery.

DIY ebikes do allow for a lot more modularity in the batteries though so you could for instance have a small battery mounted to the bike whereever you can and have a 2nd larger battery you can take in a backpack for longer/higher power rides, no need to carry around a massive battery if you aren't going to use much of it.

 

[E-HP]

The main thing I think you should think about is how you will be using it
I think I would be using both, throttle mode and pedal assist mode. I'd like to keep the pedal assist option open so I can attend group rides and ride with my friends. But when riding solo I'd like to have throttle and ability to use more power than Shimano/Bosch e-bike motors. So maybe the CYC would suit my needs better.

If you are riding offroad, and on steep narrow trails, and dropoffs, and plan to use PAS in those situations, then I would advise against cadence based pedal assist, like the BB series to avoid flying off a cliff. That leaves the crappy (Chalo;'a words) TSDZ or the noisy CYC (my words) for the popular aftermarket options. Out of those options, I'd learn to deal with the noise.

 

[tomjasz]

Unless you pick a known crappy option like TSDZ2

Like many kits appropriate depends on expectations. I’ve seen score of happy users. But they’ll never be a BBSHD.

 

[nicobie]

I think I'd run a modern hub motor with a relatively hi Amp controler. KISS.

 

[E-HP]

I think I'd run a modern hub motor with a relatively hi Amp controler. KISS.

Agreed, but I've found adding a temp sensor provides peace of mind.

 

[nicobie]

Yes, very important. I'd forgotten to mention this.

 

[calab]

Its good to see some diy ebikes out there, I'd never see them for the longest time. I guess with everyone buying ready made ebikes, people priced them out and had a bit of an upchuck on their prices and so decided to twist some wires together. Good to see.

---->You wont be able to convert a Specialized ebike to higher power or no pas. You could go for the cheaper no-name ebike, but why bother converting some junky Amazon/ebay/department store p.o.s. ebike-------> Build your own ebikes from an existing normal xc bicycle. Twist some wires together, lock some bolts down tight and go riding.

I would only suggest you go look at Luna Cycle, if I had the cash I would but its to easy to convert bicycles to ebike and build them the way you want it, on a bike, any bike you like. Hub motors are great that way, mid drives you have to look at the frame geometry a bit more.

 

[From-A-To-B]

I defer to others with more experience, but it occurs to me that bolting a 20 pound DD rear hub motor onto a mountain bike intended to be used on dirt trails at climbing speeds under 15mph is heavy, inefficient, and gives less usable power (climbing torque) than a BB motor.

Plenty of folks strap 10KW of rear DD onto a bigger frame, call it a dirt bike, and ride backcountry trails all day. But I suspect that sub-1000W systems may be better served by running that power through a transmission (cassette).

I only ride on the road and love my DD hub. Gets me up steep, paved roads nicely. This just seems like a different use case.

It sounds like you're the kind of rider who loads the bike onto a smog machine and carries it to a playground to ride…

Sounds like Chalo is a ride-to-your-ride proponent. That tracks—and one can build fitness by spending more time on the bike.

I appreciate his technical expertise and willingness to share his knowledge and shop experience.

 

[E-HP]

My frame is a Canyon torque that slopes slightly upwards from BB so I think I would not be sacrificing too much ground clearance with mid drive conversion. I have already replaced the fork and front wheel with 29er versions so there is more ground clearence than in the stock version. Pic is not my bike, but an example where the shape of the bb area can be seen:

View attachment 334128

Do you ever fall while riding? For offroad riding, I would do everything I could to get the battery mounted on the bike. Backpacks are an option, but I worry that falling the wrong way with a backpack battery risks spinal injuries more than I'm willing to take. I guess it depends on the type of trails you're riding on though. My trade off would be to go the opposite direction and convert to 26" wheels to gain enough clearance under the downtube to mount a decent sized battery, maybe like this one:

EM3ev 52V (14S4P) Super Shark Ebike Battery | EM3ev

em3ev.com

 

[richj8990]

Hello! I'm an active mountain biker with many years of experience in XC, trail, enduro and downhill riding. Last weekend I got to borrow a high end Specialized e-bike for test ride. I certainly could see the the benefits but I still did not get convinced. Because of the assist works only when pedaling and the 25 km/h speed limit, the bike did not feel that mind-blowing.

So I started wondering about building a custom e-bike and found this forum. Is converting an existing ebike really a reasonable project? I'm planning to use the bike 100 % for mountain biking, zero commuting, single track and off-road only. Are there mid drive conversion motors that are really robust and can whitstand hard enduro/downhill style riding? I am pretty confident I can come up with a solution to securely attach battery cells to the frame. If the project itself is worth starting

I read this topic:

eMTB - Specialized Enduro with CYC Stealth (aka The e-Duro!)

Hey all, figured I'd post this most recent build up for interest. Not quite a build thread as I've finished it for the most part, but it's interesting to me and maybe other folks are interested. Here she is on her first ride this past weekend: Goals of this build: A real, real, electric...

endless-sphere.com

and became heavily inspired. My knowledge of aftermarket mid drive conversion kits are basically zero. I know Bafang and CYC make motors but that is it. What kind of motor should I choose if I want to have plenty of power and a possibility to use the assist without pedaling? Basically I want a bike that I can ride as ahard as a downhill bike is intended and it should have noticeable more power than a normal 250 W ebike that assists only when pedaled.

I have a good long travel bike already that I could convert. Another option would also be that I get an used e-mtb, remove the stock shimano/bosch motor, and install something more powerfull. Is there more powerful aftermarket motors that could replace fr example a regular Shimano EP8 motor?

Thank you in advance!

The CYC would be the best choice for you (and probably 'should' have been for me too). I'm trying something cheaper right now. Don't buy a Bafang BSSxx, it most likely will not fit into your frame. They have longer boost-spec axles now, but if you look at where the bottom bracket is compared with the motor, you'll see that there is not much room between them. Modern bikes --- especially if you are already changing around an e-bike with a huge downtube --- have thick frames that make it difficult to slide in a BSSxx axle. I've seen pictures where the motor is pointing almost completely down towards the ground, and that's going to be really bad for offroading. The advantage of the CYC is that the motor and axle are separate, so you can mount the motor up where desired on the downtube.