Measure - model - analyse - change...
Old steel frame Sturmey Archer 3 Speed project
I have put an old Sturmey Archer 3 speed hub into a cheap mountain bike. Why? When it's wet, horrible and muddy and I'm just riding around in the woods for fun I'm fed up replacing expensive dérailleurs, gears, front sprocket and chain every few rides. So I built a very cheap bike with very low gears just for these conditions. Three speed chains and sprockets are much wider, long lived and cheaper than modern high spec dérailleurs. Also - I will try and enclose the chain to some degree.
I had an old steel frame and I wanted the bike to be fairly large - not too much smaller than my Specialized Hardrock. So, before doing the work I measured and compared them.
Here are the results. The Hardrock is the blue/grey frame and the steel frame is the blue/yellow one.
Not too much smaller - so I built it! The hub width on the old Sturmey Archer hub is 110mm and the old steel frame started out at 130mm. With some persuasion it's now 120mm and with a few spacers everything fits! I run a small front chainring and large rear sprocket to keep the gearing low. The 'Trail' on both was very similar. Interestingly the bottom bracket is higher. Over time will the Sturmey Archer hub take 'off road' punishment or will the axle bend?