Hub verses External gears for mid drive

[Rickidoodah]

I'm looking at build a new bike with a mid drive unit, either bbs 02 or hd.
I have a Nexus 8 hub lying around and I'm considering whether to use that or stick with external gears.
I'd be interested to hear other people's opinions before I embark on this new build.


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[RobF]

Plenty of factory ebikes use the Nexus hub, so it should work fine.

Budget hub gears can't take lots of torque so I would only use one with a legal 250w crank drive.

Chain line can be hard to sort with some crank drives kits - it's sometimes not possible to use all the gears on a cassette.

In that respect a hub might be easier because, of course, you only have one cog at the back to align with the front.

 

[Fordulike]

As RobF says, both the BBS02 and BBSHD produce a massive amount of torque, which will not be kind to your Nexus hub. A BBS01 would probably be ok, but not the most exciting ride.

Chainline issues can be (mostly) solved with an aftermarket offset chainring, although these are expensive. I personally had to fit an offset 42T, when I discovered chainline issues in the lowest two gears.

If you do end up damaging the Nexus, then it will not be cheap to replace. Rear cassettes on the other hand are cheap as chips.

Lastly, think about how you're going to deal with a puncture on either set-up. I would personally prefer the simplicity of quickly whipping the wheel off on a derailleur system.

 

[Woosh]

consider fitting a gear sensor (about £50 for BBS01 / BBS02) to protect your IGH:

http://gearsensor.com/

 

[tommie]

I'm looking at build a new bike with a mid drive unit, either bbs 02 or hd.
I have a Nexus 8 hub lying around and I'm considering whether to use that or stick with external gears.
I'd be interested to hear other people's opinions before I embark on this new build.


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Have already done what you`re thinking about!
BBS02 750W conversion, now with an Alfine 8 hub that replaced the derailleur.
Nice to be able to change gear when stationary or at a junction, straight chainline, just replace the hub cog if you want more speed or climbing ability, cheap at around a fiver, and no faffing around to get the derailleur to change properly,


you won`t need that tensioner if your dropouts are horizontal

 

[D8ve]

Replaced my derailleur with Alfine 8 spd and it's been all fine.
Slightly lowered top end over the 27 spd gears but less chainline hassle and great at traffic lights.

 

[Fordulike]

Have already done what you`re thinking about!
BBS02 750W conversion, now with an Alfine 8 hub that replaced the derailleur.
Nice to be able to change gear when stationary or at a junction, straight chainline, just replace the hub cog if you want more speed or climbing ability, cheap at around a fiver, and no faffing around to get the derailleur to change properly,
you won`t need that tensioner if your dropouts are horizontal

That's good news for the OP

 

[Fordulike]

What's the gear change like, under full BBSxx power, on the Alfine 8?

 

[tommie]

What's the gear change like, under full BBSxx power, on the Alfine 8?

I find its ok when you`re going up through the gears, but when you`re going for a hill and changing down there has to be a pause with the pedals

 

[big_gems]

Any views on sturmley archer? Was considering a 3 sp with bbs2. Also wondering if the drum brakes have enough stopping power for an e bike?

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[tommie]

think 3 spd isn`t enough and 8 spd is to much imo, i find myself sometimes changing two at a time

 

[Rohloffboy]

All the CD ebikes that I Have come across using the Nexus Alfine IGH have been using the lower torque motors, say 45nm etc, so there must be a reason for that.

In fact the Bosch website, states that there lower torque motors are suitable for IGH's.

Ebikes using the Rohloff or Nuvinci IGH often come with the Bosch CX motor which is the higher torque variant.

The Rohloff IGH is good upto 100nm, and I guess the Nuvinci 360 is the same if not more.

My intention is to get an ebike equipped with the Bafang Max Drive CD motor, and add my Rohloff hub to that.

The main issues to overcome will be chainline, and chain tensioning along with torque lockout, but all is doable.

 

[Deleted member 4366]

The Nuvinci can handle about 25 amps at 36v from a crank motor. At 30A and full torque, it slips. Bosch, Yamaha, etc run at about 20A max.

 

[Rohloffboy]

Some good info there d8veh, I was quite reassured to see that Riese & Muller are including either the Rohloff IGH and or Nuvinci 360 on the Charger GX EBike which has the higher torque Bosch CX motor.

Even the HS (45kmph) "S" Pedelec version of the R&M Charger is also using the Rohloff, although I guess the HS model of Bosch CX motor is the same torque as the 25kmph version.

Of course this tells me that it is probably not a good idea, to use a cheaper IGH like the Nexus Alfine 8/11 or any of the SRAM offerings like the Spectro P7, if you are running a high torque motor.

 

[Rickidoodah]

Thanks for your comments everyone. I like the idea of the straight chain line but sounds like I'd be better off with the slightly lower torque of the bbs02 rather than the hd.


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