Should I add a motor to this MTB bike frame or find another source?

[banshee28]

Hi... So I have been down this road for a while now and been back and forth. This would be my first e-bike so really learning alot before proceeding. I read lots of great posts here so still trying to narrow down my best options.

So I have a 2018 Cannondale Trail 4 hardtail mtb. Its practically brand new and has hydraulic disk brakes, so I figured it would be a good choice for a e-bike upgrade. https://static.evanscycles.com/production/bikes/mountain-bikes/product-image/Original/cannondale-trail-4-2018-mountain-bike-blue-EV308176-5000-1.jpg

I debated between mid-drive and rear HUB and decided rear hub would be best for me since I am not really into very technical tails or have any steep hills where I live. However I noticed the rear drop outs for this particular bike seem a little odd to me (i am not an expert so maybe this is normal) that the rear dérailleur takes some of the space of the drop outs vs the frame! I posed over on reddit and got some really good and interesting advice that this does not sound like a good/safe setup for a rear HUB! So for the most part I think I will have to drop the rear hub motor option on this project!

https://www.reddit.com/r/ebikes/comments/hfwzer/rear_drop_out_question/?sort=new

My only other choice would be a mid drive. So each has its pros and cons and if this is the only setup I can get, then I am perfectly fine setting this up instead. I like many of the advantages of a mid drive too!

Questions:

1) Would a mid drive motor setup be SAFE on this bike? It has a Aluminium frame I think and the same issues with the rear drop outs I mentioned above. I guess with a mid drive, the rear setup does not really matter much? Is the Aluminium frame vs Steel ok here? I am not really into high speed runs or super technical trails (at least not yet) so maybe its ok for now? Should I consider upgrading the wheels or spokes as I was going to do at least on the rear with the HUB option?

2) If so, I am considering a BBSHD or maybe the new CYC X1 Pro Gen2. However I almost dont want to get too heavy into modifying this so maybe a BBSHD is plenty! I dont mind paying a little more but not sure if it would make a difference for me and this setup?

3) Any other suggestions on these options and controllers/batteries etc??

Thanks for the help, loooking forward to doing this right, and hopefully DIY vs a pre-built kit.... :lol:

 

[MadRhino]

Good frame for a BB drive. With a hub you’d have to build it low power. High power hub builds requires good full suspension frames.

 

[markz]

2018 Cannondale Trail 4 has 29" wheels, not good for hub motors. Better to have 26" or smaller wheels for a hub motor. Thats why you should install a BBSHD on your 29" bike. www.em3ev.com

 

[banshee28]

Thanks guys! Yea seems like this is the right way to go vs hub! Been reading up on bbshd for a while today! Still a few things to verify before pulling the trigger.

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[AHicks]

Good frame for a BB drive. With a hub you’d have to build it low power. High power hub builds requires good full suspension frames.

I have to disagree here, maybe because the term "high power" here means something different to me. Here, "high power" might be used to describe power from something like a MAC 12t geared hub, which will work just fine on a hard tail. I have several months and a few hundred miles behind that opinion.

Then too, clueless how this new bike will be ridden. I agree it might make a great e-bike, but what kind of a mountain bike is it intended to be when done? Would likely make a great street/trail hybrid. Serious off road may be a different story. That's beyond my pay grade.

If that bike were in my garage, there would be 2 ways to go. Sell it for what I could get for it and use that toward an inexpensive OEM bike, OR, maybe fab an aluminum plate to beef up the drop out and provide a mounting point for the derailleur?

 

[banshee28]

So yea, I was also considering just getting a pre built for now as not invest in a diy kit for this frame! Does not sound like the best base for this? Was reading about igh's... then I could use a single sprocket which would make the chainline perfect all the time. So many options with diy!!!! Too many, lol.

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[banshee28]

As far as how it will be used, a little fun commuting, and eventually some light trails soon. So nothing really heavy. May put street tires on soon. So yea, I know I probably should focus on one priority, but this is step one to get into the ebike scene!!!

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[markz]

fun

You will be addicted in no time.

 

[MadRhino]

Here, "high power" might be used to describe power from something like a MAC 12t geared hub, which will work just fine on a hard tail. I have several months and a few hundred miles behind that opinion.

Yep, a mac is good for that bike, but it is nowhere near high power.

Here, the fun begins from 10kw and high power 25 kw. I see a mac as a toy that is very easy to break and even easier to fry. And I have more than a decade, about 100,000 miles behind that opinion.

But, I agree that power and speed are subjective. High for one is low to another.

 

[banshee28]

Here, "high power" might be used to describe power from something like a MAC 12t geared hub, which will work just fine on a hard tail. I have several months and a few hundred miles behind that opinion.

Yep, a mac is good for that bike, but it is nowhere near high power.

Here, the fun begins from 10kw and high power 25 kw. I see a mac as a toy that is very easy to break and even easier to fry. And I have more than a decade, about 100,000 miles behind that opinion.

But, I agree that power and speed are subjective. High for one is low to another.

Based on this, I am definately looking into "low power", lol. I think 1500 or so is what I am thinking.
Having said that, I am still not sure if that original hub motor idea was optimal based on the drop out of this frame? I actually had an order in with Grin (which has been great for support) but I dont want to risk this on a sub-par frame. :?

I may ditch the entire DIY on this bike and get a OEM for now, still deciding... :lol:

 

[MadRhino]

It would be a great bike with a BBSHD and 1 kw/h of batteries. I bet you would still be riding it after building 2 others. Bikes are calling for a type of build IMO. When I see a bike geometry, I see instantly the kind of build that is gonna suit it best. I like Cannondale frames, stiff, robust, light weight and fun to ride. The 29ers are calling for a BB drive. That is my opinion, but many would be happy with a slow winding hub.

 

[markz]

Cruisers are where its at for me.

I keep looking for a used Townie, Electra, Beach, Cruiser are the search terms I use everyday. Saw an EVO Rocky Ridge today, 1x7, fat, cruiser, but the guy wanted C$950, which is a tad more then new cost from web searches. I got my C$200 Costco fat bike, needs a layback seat post, and wheel base extended, cheap enough to mess with. My Cyclone 4kw will go on it one of these yrs.

A great source for bicycles is BikesDirect.com but they dont ship to Canada. Pinkbike is for newer stuff, usually more expensive stuff. Kijiji in Canada is what I search everyday while I am dropping a deuce.

 

[amberwolf]

High power hub builds requires good full suspension frames.

No, they don't.

Perhaps high *speed* builds would, but you can have thousands of watts available in a hubmotor with no suspension at all, when used at speeds appropriate to the use of such bikes.

 

[amberwolf]

Having said that, I am still not sure if that original hub motor idea was optimal based on the drop out of this frame?

Torque plates bolted to the existing dropouts. See the Torque Arm Picture thread, or any of the many posts about torque plates, clamping dropouts, etc. for ideas. (yes, you would have to make them)

 

[999zip999]

You need to able to fit a DD hub nut next to the derailleur. Some frames don't leave enough room between the derailleur and where the nut should go.
The bbshd should work or Mac 8t rear hub if fits.

 

[banshee28]

Having said that, I am still not sure if that original hub motor idea was optimal based on the drop out of this frame?

Torque plates bolted to the existing dropouts. See the Torque Arm Picture thread, or any of the many posts about torque plates, clamping dropouts, etc. for ideas. (yes, you would have to make them)

I just took at look at many of those threads! Wow, did not know there was such a large discussion on these, but I DO see why now!!
Thanks...
I also see there is a pretty big difference between a "generic" TA such as a Grin V4 vs a custom one based on the exact bike. It sounds like the gereric one may be ok but the custom one will be stronger and hold more power and/or for longer life. I was originally going to simply use the Grin TA since I am not able to custom fab one of these myself! So far I think my best bet as many of you have pointed out is simply focus on a mid drive (BB) and drop the hub idea.

So for now that is my plan! BBSHD and will figure out the chainline and possibly dropping a few cogs to leave only 4 or so since I wont need the 11 I have now with a BBSHD! :lol: :lol:

 

[banshee28]

I see a mac as a toy that is very easy to break and even easier to fry.

Hi... So just curious here... I was actually planning a 9C DD hub but its prob close enough to a MAC, just not geared. Why do you say this about the MAC? Is it due to it being geared or a hub?

 

[markz]

Geared motors have more parts to them, and the gears can break. A direct drive motor is more durable as there are no moving parts aside from the rotating assembly. All there is are bearings, magnets, windings, laminations nothing to break easy. If you use a geared hub motor well within its power limitations it will be fine. There is a more noticeable whine to it as the gears mesh and touch each other, but others have said that if you use a sinewave controller that the sound reduces abit. Direct Drive motors can have no sound, but with cheap trapezodial controllers there is a noise that can be heard, so you just buy a sinewave controller and there will be literally no sound aside from the tire tread.

"Custom Fab" a torque arm, is as simple as getting an angle grinder and some 1/4" x 1" x 4' flat plate from Home Depot and some hose clamps. Heck, I've been using the rear derailleur hanger off an old Shimano on one side, for 36V 40A of power, 375lbs total weight, and a washer with the nub on it for the other side. Something like this - https://www.ebikes.ca/shop/electric-bicycle-parts/torque-arms/torqarm-8mm.html
it does bite in, but I would use something better to be sure.
Out of Stock at the moment - https://www.ebikes.ca/shop/electric-bicycle-parts/torque-arms/torqarm-ez.html

 

[Balmorhea]

I see a mac as a toy that is very easy to break and even easier to fry.

Hi... So just curious here... I was actually planning a 9C DD hub but its prob close enough to a MAC, just not geared. Why do you say this about the MAC? Is it due to it being geared or a hub?

Don’t mind him; he only likes motorcycle hub motors that weigh as much as a good bike all by themselves. MAC is the most robust and proven of the commonly used geared motors. Nine Continent motors have a pretty good track record, too.

 

[MadRhino]

Geared hubs just can’t survive my riding style and power requirements. Gears and clutch, and a fast spinning small motor with poor heat shedding ability...

Don’t get me wrong. They have a place in the ebike market, and as you can see some really like them. There is a type of bike for every usage. My usage now, is ULM commuting and MTB motor sport. Fried small motors had filled a garbage can in my shop.

 

[ScooterMan101]

What speeds are you wanting to ride at ? and for how long at those speeds ?

Remember : the faster you go the more you will need full suspension , and quality suspension makes a huge positive difference .
Slower speeds and a hardtail will be fine, a seatpost like the Thudbuster LT helps .
Slower speeds for many of us are speeds under 17-20 mph.

1) Mid-drives chew up a drive train several times faster than a Rear Hub and put stress on the Paws/Ratchet of the Rear wheel freehub . so be prepared to spend much more money on Chains/Chainrings/Cassettes/Rear Hubs/Brake Pads.

2) From what you describe of your local terrain and riding a rear hub will work better.

If not going fast you do not need a heavy DD hub , a smaller geared hub will be fine .

When you do a e-bike conversion you most often have to make things work such as , with your rear frame dropout design you will have to use some small washers to get the big washer and nut out far enough from the frame.
Just drill out some small washer/spacer and file the area towards the top where there is less room. ( this will also work as a low power torque arm when being precise with the washer mod. )

Grin Technologies has determined that 80% of people will be better off with a hub motor . after building up and running both ... several rear hubs and one mid drive I agree with them .
I had a mac motor , it was great , was only 10.5 pounds built up into the wheel and did most everything except for riding up very long and very steep mountain roads .
The rear hub I have on a bike now is 15.5 pounds built up in the wheel, and the next DD I will be using is 17 pounds built up onto the wheel .
The 10.5 of the mac hub/wheel felt better, I am only using DD rear hubs now because of more speed , more hill climbing ability and higher voltages than 52 volt .
Depending on speed you might even be happy with a smaller motor than the mac , Grin sells those also .

 

[banshee28]

So not too fast, 30Mph tops is plenty.

I figured the DD 9C RH212 rear hub was a good choice for the speed and terrain i was going to use this for. I think my only concern here is simply the drop outs and making sure whatever TA I would have to use would be appropriate and safe!

I know everyone will have their own opinion and experiences and there are very clear pro's and cons to hub vs mid drive. I am good either way, but for this project (my first build) was thinking hub would be easier overall and hopefully more reliable. So still trying to figure this out, and like you said maybe I will have to "make things work" a little so I will have to get some tools ready 8)

 

[MadRhino]

Pros and cons about BB drives and hubs are not that clear. I build with hubs and usually recommend hubs. Still, the light weight Cannondale 29er MTB that you have is a bike that I would build with a BB drive. Not because of its dropouts, for I always make custom dropouts for any hub build. Not because it is Alu, for all the bikes that I build are Alu. I would build it BB drive because I find it must retain the bicycle feel in weight and handling. Because it is what this bike is about in the first place: a well balanced light weight bike that is an easy to control, comfortable ride.

Some reasons would make me build it with a hub nevertheless, the main is:
If it is built as a daily commuter, because traveling to work all year long does require a DD hub IMO, for all weather long term reliability.

Also: If it will be pulling a child trailer or have a child seat installed. Because if the balance of the bike will be compromised anyway for utility usage, there is no point to care about its balance and weight.

 

[amberwolf]

since I am not able to custom fab one of these myself!

Hacksaw. Drill. Files. Patience.

 

[amberwolf]

I was actually planning a 9C DD hub but its prob close enough to a MAC, just not geared.

Geared usually means more torque for the same power level, but less able to sustain the max power levels over longer periods (see the http://ebikes.ca/simulator ).

If you mostly need the torque for startups with cargo/trailers, it doesn't matter. If you need it for sustained long hill climbs, it might.