Thoughts on adding a BBS02 or front hub to an Alfine 11 urban bike?

[Andrie]

Hello fellas.

Looking for advice on converting my BMC Alpenchallenge 01 urba commuter to an ebike. I have been toying with the idea of either adding a front hub motor or a mid drive. I have heard concerns for both builds.

For the mid drive, I've heard that the Alfine 11 might not withstand the torque from the BBS02. But most of those comments seem to be speculative and there seem to be a few Alfine 11 BBS02 out there according to youtube.

For the front I've heard that you should never use a front hub on a carbon fork. Yet there are plenty of users who have used torque arms and have gone thousands of miles on carbon forks with front hubs with no issues.

Also does anyone know what the BBS02 conversion process is like when you have a carbon belt? Does it require some special parts or can I attach it like I would on a non carbon belt bike?

 

[harryS]

That's too nice of bike to break by hanging on a motor, especially one that stands upright with no kick stand.
Front hub motor on carbon forks is high risk. Bafang middrive might crush the BB, unless it has a metal tube.

Get a cheaper bike for the ebike conversion. Weight doesn't matter as much with a motor.

 

[Andrie]

That's too nice of bike to break by hanging on a motor, especially one that stands upright with no kick stand.
Front hub motor on carbon forks is high risk. Bafang middrive might crush the BB, unless it has a metal tube.

Get a cheaper bike for the ebike conversion. Weight doesn't matter as much with a motor.

Haha @ upright with no kickstand. But thanks for the input, appreciate it.

I'm not that fussed about the niceness of the bike to be honest. I got it second hand for around $800 and I rarely use it. So I would be okay with something going wrong.

I feel like a small front hub motor and a small lightweight battery would be fun. Is a motor on a carbon fork that much of an issue? I'd get a small motor like the Bafang mini G311 and torque arms.

There are people out there that have 2-3k miles with very high powered front motors on their carbon forks and they haven't had any issues.

 

[rannyv]

Assuming that the frame is aluminum, I think it would be OK with the BBS-02. I use BBS-HD (1000 vs. 750 watt) on a steel bike with an Alfine 8 speed. It's gone 1400 miles without issue. Common sense when shifting is required.

I agree with @harryS - don't add a hub motor to a carbon fork. I also agree that it's too nice a bike to muck up with wires and add on kit parts.

 

[rich c]

Carbon forks are great, until they aren't. And when they are not right, they fail hard and fast. I agree, no hub motor on carbon forks.

 

[Andrie]

Thanks for the input guys.

Even though pretty much everyone here is telling me it's a bad idea, I'm thinking about adding a G311 bafang mini 250w front hub with a Mighty Mini 52V 7AH battery pack. Justin at Grin said the fork should be okay with such a small motor.

I figure with such a small battery and such a small motor the build should look fairly clean. I could probably fit the battery in a bag like this. Might put the controller in there too. Thoughts?

 

[rich c]

Personally, a feeling like "should be okay" is not a safety factor I like. A failed front fork will result in broken bones. Good luck!

 

[CodyDog]

The risk of a broken carbon fork is much higher than a steel fork. The risk-reward factor is what I would be concerned with. The intergraty of your carbon fork will be compromise somewhere along the line. The fact that some have done it does not change the dynamics of carbon in a fork that was not designed for what you are wanting to do.

There added weight will effect the carbon fork with an increased load factor each time you brake or hit a bump. The carbon fork is designed with a proof load. The carbon material must remain in its elastic region which is typically 85-95% of the yield strength. Adding the hub drive will take you near or out of the limits of the intended design (proof load).

I am one to push the limits but having failure of a front fork at 20 mph is not something you will want to experience.

 

[indianajo]

Used bikes in my area go $40-70 at Salvation Army, the flea market, etc. Not all charity resale shops have them but some specialize in them like SA.
I converted a 70's huffy savannah steel frame with a front motor, had to grind out the fork slots to fit the axle. $35 at New-to-You charity resale. You don't want to grind out a $800 bike. You'd probably set fire to a carbon fork with a grinder.
Conversion is not that hard, do it twice if you're really sold on this bike. Making the brackets to mount the display, controller, battery are the time consuming parts, and those could be moved. I had to make a bracket to hang the PAS sensor, since crank design changes every 10 years. At least the crank arms won't go loose every 50 miles like the oh-oh's PO* mountain bikes. Also the steel fork from a donor bike probably will fit this one if it is the same wheel size. If not, get on craigslist and buy a $150 bike. At those prices, cables will be frozen or something, $2 parts. You have to go into the brakes anyway to hook up the stop switches.

 

[thewardenofnorth]

@Andrie have you gone through with it?

I was thinking of trying something with a BBS02 or a BBSHD and a second-hand ALPENCHALLENGE AC01 ONE (the TWO has the Alfine 8, so it might be a better option to slap a motor onto it).