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Old 12-14-19, 05:29 PM
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Run in medium gear, direct drive, a Sturmey is 100% efficient. How much power is lost to heat in high or low gear is not resolved, different authorities have different answers. In any case running with close ratio hubs is going to be much better than running the typical AW. The vintage hubs you are thinking of would be all or mostly hand machined gears rather than the later powder metallurgy cast gears. You are always running in perfect chainline and there are no pulleys.

Some practical considerations. I am no Sturmey expert but I believe these hubs (AR, AC, AF, FC) will all be 114mm over locknut. 4-1/2". The older ones might be even narrower, won't be wider. There's a limit to how many washers you want on the axle and an absolute limit before you have to come up with a longer axle. Which you will have to make.Most of the ones you will find will have threaded drivers which makes it easy, use a standard fixed cog. Old AR hubs might have the real old spline pattern, not sure. Almost everything you will find will be 40 hole, so use 20 spokes one cross or two cross and a rim strong enough to hold up. That would be lots of modern aero rims.

Which brings us to another point. The old times you are looking at are all aero-nothing. Even the clothes are not that tight and in some cases are quite loose. The roads just might be smooth for a few 25 mile courses. None of the longer courses will be on good pavement. Most climbs, even small ones, will not be that well graded. Everyone is using position and pedal style derived from need for survival on rough roads. That style could in some cases be aero, witness Greg Lemond or Fausto Coppi. But it was not something they much thought about and you can see it. Most of these rides will be on tubulars but there will be no light tubulars except track tubulars and those would only be used on short and unusually smooth courses. Rims were as light as now but of course they were flat. And everyone will be on 40 spokes rear 32 front.

Unless one of these lovely old hubs just falls into your hands I'd suggest having a go at fixed gear before starting the search for an old hub. Also limit the search to hubs in top condition, low miles. You aren't finding parts except by sheer luck and the English racked up big miles and were hardly noted for good maintenance.

One of the standard tropes for old English TTs, limited of course to the top riders, was to do early season TTs on the winter bike. WIth full mudguards and clinchers. Those clinchers were slow. Standard gear, "medium gear" of 48x18 fixed. Don't switch to the geared bike until you beat the hour for 25 miles in that 72" fixed. Yes, you can go fast without all the latest.
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