Of course I f...d up

[AenderW]

...and ordered the 750 watt BBS02 with a 52 teeth Chainwheel

I hadn't quite the right size of original Nexus chainwheel in mind and was horrified when I noticed, that that one is 38 teeth.

Does it make sense to mount the kit with 52 chainwheel on the Nexus 8 gear hub???

I don't know too much about torque and stress on the Nexus Inter 8 gear hub on the rear.

I consider myself "sporty", meaning that when commuting throughout the city (+- 15 miles/26 km a day), I never take the first three gears. I start off in fourth.

 

[flecc]

...and ordered the 750 watt BBS02 with a 52 teeth Chainwheel

I hadn't quite the right size of original Nexus chainwheel in mind and was horrified when I noticed, that that one is 38 teeth.

Does it make sense to mount the kit with 52 chainwheel on the Nexus 8 gear hub???

I don't know too much about torque and stress on the Nexus Inter 8 gear hub on the rear.

I consider myself "sporty", meaning that when commuting throughout the city (+- 15 miles/26 km a day), I never take the first three gears. I start off in fourth.

Sounds it could be ok for your style of riding, a fairly high gear range. Also the larger chainwheel means less torque stress on the hub gear, it's having very low gearing that's their weakness.

Assuming you have 700c wheels and a fairly standard 21 tooth sprocket on your hub gear, your gear range will be 35.4 to 108 inches, one that would also suit me.

Of course you can fine adjust with different rear spockets on the hub gear, anything from 16 to 24 teeth.
.

 

[AenderW]

Hm, okay.

As the kit arrived already yesterday, I will go ahead and post my results. It took only a week from mainland China to Europe, which I consider very fast...

Just to be on the safe side, I ordered a spare 44...

Will it not be too much fiddling to change just the chainwheel after the Bafang is on the bike as a whole?

 

[trex]

you may need a chain tensioner if you want to keep the option of swapping chainrings. I still think 750W is too much power for the Nexus 8

 

[flecc]

Hm, okay.

As the kit arrived already yesterday, I will go ahead and post my results. It took only a week from mainland China to Europe, which I consider very fast...

Just to be on the safe side, I ordered a spare 44...

Will it not be too much fiddling to change just the chainwheel after the Bafang is on the bike as a whole?

You may have missed my edit above when I added the gear inches, showing that you'll be perfectly ok on gearing.

A 44 tooth will give you this gear range under the conditions I quoted, 30 to 91.6 inches, suited to average fit cyclist.
.

 

[AenderW]

you may need a chain tensioner if you want to keep the option of swapping chainrings. I still think 750W is too much power for the Nexus 8

I will shorten/lengthen the chain to fit my needs, no? If that is what a chain tensioner does. I don't quite know that item (looked it up on google).

My Nexus has already 10.000 km done. So if it will start creaking, I can still exchange it. Time will tell...

 

[trex]

Shimano recommend not loading their hub gears for more than 250W. They void the guarantee if you do.
Chain tensioner:
http://www.ebay.co.uk/itm/Shimano-CT-S510-Alfine-Chain-Tensioner-for-HUB-GEARS-and-Singlespeed-bikes-/201344505804

 

[AenderW]

Ah now I understand, however I have horizontal dropout, so I will be able to adjust.

Well I will not tell the hub what is going up front. Maybe it will not notice

 

[AenderW]

Doing the first commuting trips.... what a joy. That big 52 chainwheel up front was just what I needed, to get a calm/relaxed pedalling attitude. The fast pedalling, I will keep that for sporting around on the Mountainbike.

Definitely not regretting this retrofitting to my classic Trekking bike (Trek L400 Navigator, 700c, Nexus 8, Rollerbrakes).

I simply "overhear" the occasional "whack" from the Nexus, but that is coming rather because of the unaccustomed inner working of the Bafang. It tends "to come" the moment you shift to high gear. I'm regretting a torque sensor there...

 

[flecc]

Doing the first commuting trips.... what a joy. That big 52 chainwheel up front was just what I needed, to get a calm/relaxed pedalling attitude.

I thought that was going to be just right for you, judging from how you described your preferred way to cycle, very much my type of gearing. On my 20" wheel e-bike I have a 60 tooth chainring to make it similar.
.

 

[AenderW]

Update:

As I had, in my first panic reaction, ordered a 44 teeth front chainwheel, I mounted that one week ago during cleaning and oiling my bicycle. I was fearing that über-big 52 teeth front chainwheel would be 'too much'.

After less than 100 km in that configuration, I will retrofit ASAP to 52 teeth. The 44 does not make that much difference to the original 38, but it's a huge step down from 52. As in the 38 t config., I'm not using gears 1 to 3 any more.

Interesting fact is that I'm also draining my batteries around 10 % faster...

I have the general feeling that the pedal hub and the Nexus 8 are strained more.

So, more fine-tuning to come during Christmas holidays.

 

[anotherkiwi]

Moving from 42 -> 48 has raised my average speed by 4-5 kph and not increased battery use. This is with a hub motor of course. I also use the full range of gears except for the 34 tooth granny "get me home over the hills just in case" gear. I am currently looking at 50-39 cranksets...

 

[AenderW]

Imagine the original front chainwheel on that Trek-Trekkingbike was around 34 I think. It was almost impossible to get more than 25 km/h in the 8th gear.

My everyday's commuting trip profile tends to be a frustrating, 6,4 km one-way, 5 uphill full stops, uphill riding through a park sharing with many pedestrians (slow riding)...

I hooked up the watt-meter on some of the trips, I get around 820 watt in, and a max consumption on full assistance of about 22-25 amps. Speed average is about 20 to 25 km /h. In these wintery low light/wet conditions, around 20 km/h.

I really am happy to have built this bike.

On my maxi-scooter, the trip is just a bit shorter, maybe 5 minutes, but much more dangerous, and I'm loosing that advantage again preparing and wearing/taking of motorbike outfit and helmet...

This month's km on my bicycle was 350 km, Scooter not even 50...