Shopping list assistance

[Andybg]

Hi Matt

Glad to hear you tour went well. Sorry that the chain ring gave up the ghost. Mileage wise on the transmission pre your ownership of the bike:

Rear cog and chain: circa 1500 miles
Chain ring circa 50 miles

The  chain ring was a cheap one and bought as a quick fix as the bike was running a 44? chain ring and was well over geared for me.

On the whole the 38/17 gearing seems to fit most peoples needs and gives the benefit of the possibility of fitment of a chainglider if desired. I had planned on replacing it with a Surly SS one but had just not got round to it.

All the best

Andy

[Andre Jute]

The Surly is thinner and fits inside the chainglider.  The thorn is a bit too thick to rotate smoothly.If you get the surly you'll need some spacing washers to go with the chainring bolts.  SJS advised me to get these as they help centre the chainring -they are not needed on the Thorn as it is recessed.

Those spacing washers are (or was) actually part of the "scope of supply" of a new Rohloff box. For instance, I got a set with my bike. But Thorn may either not get them in the OEM kit to keep costs down, or not supply them because most customers order the thick Thorn chainring, and presumably replace like with like as it is a good, longlasting component, so they never need the spacers. But SJS stocks them, so it's one thing less to worry about sourcing..

Note that it is important to get the Rohloff chainline right to within a millimeter of 54mm. It's not as hard as you might think because once you've taken up the major distance with the spacers on the spider, fine adjustments can be made with easily available shims on the bottom bracket. I got mine spot on when I changed bottom bracket types and cranks and chainrings at the same time on my -- first assembly; it wasn't blind luck, as I'd spent hours working it out and corresponding here, getting a lot of help, until I was clear in my own mind precisely what was required.

[John Saxby]

Matt, a few followup bits & pieces,

1)    The Surly stainless ring:  As geocycle has mentioned, this is thinner than Thorn or other alloy rings, and thus accepts the Chainglider.

2)    As for chainline and spacer washers:  I can't be sure about this:  I don't think that my shop used spacer washers, and my chainline is 54 mm.

3)    For the C/glider rubbing on the rear seat-stay:  I noticed that there was just a wee bit of interference between the two, the outer curve of the seatstay and the inner-top corner of the sprocket-encasing bracket of the 'glider.  I nipped about 1/8" off the latter with a sharp knife, problem solved.  I slid a bit of black plastic electrical tape onto the stay, just in case. Appears that the fit of the 'glider varies with the different Thorn frames, to judge from my experience & the comments of Dave S, geo, & julk.

Good luck with all this in any case,

John