silveralien81

I'm considering the possibilities of converting my Priority Classic Plus Gotham Edition bike into an e-bike. My concerns are the aluminum frame and Gates Carbon Drive. My research leads me to understand that putting a hub motor on an aluminum front fork is a bad idea. That leaves mid or rear drive (trying not to have to replace the forks). Are there motors/hubs that will work with a Gates Carbon Drive and Shimano Nexus 3 gear hub without serious modding? My use case is basic commuting/grocery getting. There are considerable hills to overcome (the main reason for looking into this) and I am not light(210lbs). I am not looking for anything over 20mph on flat terrain, just some help with hills so I'm not a sweaty mess at the top and a boost on the flats when I'm feeling a bit lazy.

2old

Sounds like a classic case for a mid-drive IMO. Agree with you not to put a motor on an aluminum fork EXCEPT the one developed by Justin @ ebikesca. Have no experience with belt drive, but think it's a big project.

dilkes

I have a similar style of bike - aluminum frame, Gates drive, Nexus 3 and I put a front wheel hub drive on it. The front forks on mine are steel. You can check this with a magnet. According to the Specs Page for the Priority Classic Plus, it too has steel forks, so if this is the case, you should be OK. I would for sure verify that and still use torque arms for a front hub mount.

silveralien81

Thanks. I just looked that up and you are right. Now I feel dumb. I'll verify with a magnet when I get home. I have looked at the Grin torque arms that attach to the fender eyelets and they seem quality. Do you have any recommendations for a 500w front hub kit? Wheel size is 700x35. Budget <$1000.

NoPhart

Bafang BBS02B belt drive is possible with 68mm (and possibly a 73mm) BB and a wide enough belt line rear hub. Here's my Soma B-Side Gates Carbon Drive build. It has key belt line measurements in it.

https://www.bikeforums.net/electric-...n-build-2.html

I just made up a quick reference chart for some key Bafang BBS02B chain/belt line issues in preparation for my next build.

~55mm = BBS02B on 68mm with current spider adaptor and 50T Gates on the Soma B-Side
54.7mm = Rohloff 14spd speed hub chain/belt line
44mm = Sturmey-Archer RX-RK5 5spd (42-46mm range depending on cog)
~22mm = BBS02B spider mounting surface to right BB edge
~56mm = BBS02B on 68mm BB spider mounting surface to frame center line
~58.5mm = BBS02B on 73mm BB spider mounting surface to frame center line
~10mm = 42T Lekkie Bling Ring inset from BBS02B mounting surface
~12mm = BBS02B BB right edge to 42T Lekkie Bling Ring chain line
~46mm = BBS02B on 68mm BB with 42T Lekkie Bling Ring chain line
~48.5mm = BBS02B on 73mm BB with 42T Lekkie Bling Ring chain line

In short, the best rear hub for a BBS02B conversion is a Rohloff with it wide chain/belt line. If a 3spd is desired, the Sturmey-Archer CS-RK3 gives you a rear cassette to align the chain/belt. And, the smallest Gates front belt ring that clears the BBS02B gear reduction housing is a 50T.

One always has to consider the chain stay clearance as well. If using a 73mm BB, you can face off as much as you can until the BBS02B is right on the chain stay. In order to make a 73mm a 68mm, only face off half the difference or 2.5mm. The left side can stay where it is and you end up with an offset 70.5mm BB.

If you have access to a machine shop, then you can combine a 42T Lekkie Bling Ring and a Gates 50T to get more inset. This requires machining out the Gates 50T and machining off the Lekkie chain teeth, then heli-arcing them together.

Hope this helps if you go with a Bafang BBS02B, AKA “The-Silent-Reliable-Gaint” 750W/48V mid0drive motor (I’d keep it stock as designed) that gives “you” total control over settings. IMHO the Bafang BBSHD has too fast of a cadence if you like to pedal; stick with the stock BBS02B.

silveralien81

Thank you for the very thorough answer. I just heard a very loud, very distinct WHOOSH noise just now reading your comment, lol. I think I got about 10% of that. I am a total noob at this e-bike thing. I consider myself pretty mechanical, and I repair complex electronic and mechanical systems daily. However, I do not have access to anything other than basic home tools (no machining/welding gear). It seems like this might be moot anyway since I just discovered I can safely install a front hub (super easy-no mod install).

Nelson37

You have done good research on the forks, however there is much you still have to go.

Unless you plan to pedal assist almost constantly, and most especially on the hills, that bike is really not a good candidate for what you want. A crank drive might be the best option, but not without extensive modification.

A powerful geared or DD hub would do it with minimal pedaling, but mounting such on the fork is a bad idea.

A less powerful, front geared hub, in those size wheels, is either going to overheat and melt climbing any major hills, (on which length and height numbers might be useful) without huge pedal assist help, or is going to have a max speed a LOT lower than 20 mph.

EX - my geared mini front hub - wattage numbers are largely useless - which does 260 RPM unloaded on 36 volts - those are the important numbers - in a 700c wheel cruises at 18 mph on flat land, and definitely helps on a hill, but hill climbs MUST be 10 mph or higher or less than 30 seconds, or I get off and walk. The large wheel is like putting the motor in a very high gear speedwise. Slow hill climb can cook a motor in 90 seconds.

"Hills" in my area are bridges and overpasses, there is a significant hill on my way to the grocery store that is about 10 feet high and maybe 80 yards long. Your considerable ones might be slightly different.

More speed, less hill climb ability, more torque, less speed, try for both, you have too powerful a motor for a front mount.

silveralien81

Honestly, I like pedaling, and 20 mph unassisted is not really something I need (sounds fun though). The dealbreaker is the hills. Again, I can put in work to help the motor but the hills here in Seattle are fairly steep and very long. I am currently taking a bus up a hill about a mile long with varying grades and the steepest (probably close to 10% grade) 1000ft at the end, so torque is priority one. What kind of torque range would get me up a hill (w/ pedal assist) like that without burning itself out?

dilkes

My bike also has 700x35 wheels. While it may not be the absolute best solution, I have a Golden Motor Edge kit on the front wheel right now. It is a direct drive motor (500 watts +) at 48V, throttle only, and on the flats I can get to about 38 Km/h (23.5 mi/hr?) and I weigh about 240. I have 2 Grin torque arms (which can also be purchased from the Golden Motor site) although one is likely enough.

Nelson37

Now that I know that your primary need is to climb steep, long hills, which you do not currently attempt with pedal alone, I can make a reasonable assessment.

That information should have been in your first post and saved some time.

Something like a 201 RPM Q128 @ 36V, MIGHT work, IF it was in a 26" or 24" wheel, Maybe a 12T Mac, which should not be front mounted, IMO, but for your bike, and your need, a crank drive kit is the most practical solution, BUT the belt drive is going to require a LOT of modification to the kit.

You should check the simulator at ebikes.ca for a wealth of useful info.

If you have any knee issues, the pedal offset of a crank drive might cause you some problems. Not many reports from belt drive users to really have a sample size for longevity issues as affect more standard drivetrains.

It is really the wrong bike for an Ebike kit to do what you need.

NoPhart

As others have said, the Priory Classic Plus really isn't the best choice for an ebike conversion because of the rear hub and brakes. The 3sps rear hub on this bike has foot brakes (can't be used) and second the front brake is not disc (preferred). If you really like this bike then take a close look at the Priority Continuum Onyx at twice the price, but it's really three times the bike. The Onyx has a NuVinci N330 rear hub with disc brakes, front dynamo hub with disc brakes that powers the headlight and fenders. You might be happy pedaling the variable N330 belt drive without a motor, but if not the Onyx has the proper components for a Bafang BBS02B mid-drive conversion to be a safe ebike. Tektro even makes hydraulic brake levers with Bafang power cutoff wires for these brakes (I'm using Tektro E350 on my next build). The NuVinci N330 might require a custom made front belt ring to retain the Gates CDX Carbon Drive, but a 42T Lekkie Bling Ring and chain rear cog will work fine. With all that said, you are looking at an absolute minimum of $2,000 total investment if all goes well.

The other more cost effective option is to search for a Bafang BBS02B 750W/48V pre-made mid-drive ebike for somewhere between $1000 and $1500. They are out there. Even a last years model heavily discounted Haibike or other manufactured city commuter ebike will meet your needs and budget. I have seen quality Haibike city ebikes sell for under $1000 on eBay brand new. These are New Old Stock (NOS) that dealers just want off their floor.

I prefer the BBS02B 750W/48V add-on because of the user control over all settings and the fact that I am a 230lb Clyde.

Good luck in your search.