Originally Posted by
colonelclink4
I recently called Sturmey Archer. I found out the spacing differences for their 8 speed XRF8.
The hub's spacing is 115mm. The brompton frame ranges between 109mm and 112mm depending on the year and model.
However, I just thought of a SNAFU. The hub requires either a 25 or a 23 tooth cog. That would probably interfere with the chain tensioner. There are other chain tensioners on the market though right? Anyone ever tried this before?
My recollection is that the chain tensioner is not the issue with the XRF8; although I believe you are on the right track. The problem is that the smallest cog that can fit on the hub has 19 teeth. The largest cog that can fit in the present configuration of the rear triangle is 17 teeth.
Now that I think about it, my memory is bad enough such that it might be the tensioner; but I recall that the chain would have to go through one of the stays if the cog were bigger than 17 teeth. The guys and gals at BromptonTalk discussed this issue at length some time back.
-G
EDIT: You can get the 19 tooth cogs at the Harris Cyclery among other online shops. You can also get the cogs for 1/8" and 3/32" chains as well in all three sizes ... 19, 23, and 25.