Winfried

Hello,

Some people I know have a couple of Dahon folders that have a Nexus 7 gear hub.

With a 245% range, those bikes are fine for small rides in relatively flat areas, but don't have enough gear range for travelling.

I have a couple of questions:

1. I read that some people installed a double crankset for use with Nexus/Alfine gear hubs, although the ratio blows away Shimano's torque limitation: How reliable is that solution in practice?
2. How easy is it to replace a Nexus 7 for a Nexus/Alfine 8?

For instance, a Nexus 8 + 16T cog + 50/34T crankset would provide a gear range of 1.6-7.4m.

Thank you.

fietsbob

2 pulley chain tensioner and you can give it a try.. they're like a short cage RD

make the low gear within the range acceptable for the hub , big ring higher than that will be fine..

I've only used the big reduction gear 2 speed crank on my 3 speed.
It does not use an internal gear change, just changes the application..
the gears themselves never shift, only the pawls ..
(My Brompton, with a mountain drive crank.. ) 54: 15

Rohloff * gives you a minimum but higher gears are said to me fine ..
so the hub in my 20" wheel with a 53t chainring is better by their suggestions,
than the same hub in a 26" wheel with a 38t chainring.

* I have the manual for that, not for the Nexus, but you can find the one for your hub, online ...


Order a pre built wheel from your favorite bike shop, through their wholesaler is simplest..
maybe go for their 11 speed and that will be wide enough a range?

....

Winfried

I might stick an eight-speed Shimano Nexus hub into a Brompton.

Apparently, cogs for that hub have a three-tab spline.

However, the smallest cog is supposed to be 16T, which might rub against the chain stay.

I notice…
1. a 14T cog on eBay
2. Brompton cogs from Sturmey-Archer have a three-tab spline.

Do you think I could use that 13T cog instead?

Thank you.


--
Edit: I notice some cogs are for an 1 1/8" chain, while others are for a 3/32" chain.

Does it really make a difference when used with a gear hub, ie. a single cog on the hub — I might add a double crankset in the front later, though?

Schwinnsta

I can not answer question knowledgeably as I have not done this. I would stay with the 3/32" stock chain just because that suits chain wheel and the derailleur/tensioner.. I am curious as to how you are going spread the chain stays? I seems scary to me with such short says. 112 mm to 135 mm, I think.

Winfried

I had it done by an ol' timer

But since it was a first, until I have a Nexus wheel in there, I can't be sure it works — chainline, tire and/or spokes rubbing against the frame, front wheel not hooked right onto the frame, possibly other issues I can't think of at this time.

--
Edit: "Shimano Nexus and Alfine cogs will work with either 1/8" or 3/32" chains" (source)

Geepig

The Sturmey Archer shown there is also a flat sprocket, while the Shimano is dished, which might be an important consideration if you are worried about the chain hitting the chain stay. I have seen both flat and dished sprockets on my Romets when I buy them, and the dished one's have noticeable chain rub on one side of the sprocket.

Winfried

Good to know, thanks.

Winfried

Using the 8L+8R blue+green anti-rotation washers, I notice the pulley arm of the Alfine 11 cassette joint is way too low when fit inside a Brompton rear triangle.

Would one of the other pairs (5, 6, 7) solve the issue?

Schwinnsta

It looks like you bent the drop outs rather than separating the stays (which would be scary, to me).

Winfried

I had a seasoned professional do it.

AFAICT, he bent both the stays and the drop outs.

Schwinnsta

It looks like where the drop outs are bent is holding it out of position.