Having had to use a larger chainwheel on the Speedwell popular, I found the gearing too high on starts and grades at 48x18T, up from the original 44x18T.
The “new” cottered crank set is one that I have had for many years and while it’s not as nice as the delicate spidery original one, it was the best I could find at short notice without using a tapered square modern crank that would be even more out of character.
So changing the rear cog was the way to go, and like the Malvern Star 2-star the cog on the old coaster hub is a standard thread “English” 1/8″ track style cog. These are relatively cheap up to 16-18T but beyond the 20T mark they are harder to find.
Surly makes a range right up to 22T in both 1/8″ single speed and 3/32″ derailleur widths however, so I ordered a 22T to try. Believe it or not, while not horrendous, this cog cost more new than the entire bike did on ebay ! (I did get the bike at a very good price though, as it was neither going nor complete).
The top secret cog supplier was an online UK outlet – if you google them you will most likely see 1000 sites for a kid’s pop group that rhymes with “giggles” so just leave off the “s” on your search (teehee).
To do this “gear change” you need a chain whip to move the (right hand threaded) cog and a C-spanner for the lockring – (it’s left hand thread btw). I use copper-slip anti seize compound on the threads too, so it’s not a nightmare job next time … put the new ones on by hand at first for a few turns – if you have to force them then something is wrong, so re-check before going further (The Golden Rule of Threads).
Also check the tightness again after a few rides, as the lockring can become loose when the cog tightens further under pedal pressure.
It’s also lucky I didn’t shorten the new chain when I fitted it a while back – it now fits about right with the wheel lining up more evenly with the mud guards (fenders) …
With the drilled holes and silver colour this cog (compared with the old one) somehow looks like the bike equivalent of fishnet stockings on the grand old dame, but I like it anyway !
Single speed gearing is always going to be a compromise – too high on starts and hills and/or too low at higher speed – I hope I don’t find this gear too low, I used 48x20T on the Malvern Star and that’s a good all round gearing for me, but I thought this bike should be a fraction lower. It feels right on a quick ride. We shall see.
Incidentally, with a back pedal coaster braked bike the braking effort should also change along with the gearing, in this case needing less pressure but with a longer stroke, though it’s not all that obvious here.
Anyway, enough philosophy, I’m off riding.