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.
a different bike - but this is the proper style of crank
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 22T looks huge ...
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).
compare the old 18T with new 22T
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) …
the hub's cog thread is now not visible - the thread showing is waiting for the lock ring
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 !
now 48T x 22T on 642mm westwood rims (28 x 1 & 3/8 ")
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.
you can just see the lock ring here
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.
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