DATE: 2018-07-25
AUTHOR: John L. Godlee
The bike that I normally use around town is in storage for the summer, and I was missing having a bike. I've also been wanting to refurbish an old bike for a long time, to learn skills and understand the mechanics and compatibility issues with building bikes. I found this BSA Tour De France on Gumtree for £30 and it immediately got my attention:
I decided to make the bike into a single speed, as I've already got a decent geared bike, so I set about stripping it down, removing the rear derailleur and the down-tube friction shifter.
Lots of people suggest using a single speed conversion kit[1] to change the gear setup, but these rely on the rear wheel having a cassette on the backwheel, rather than a freehub. Sheldon Brown[2] has a good guide on identifying whether you have a freewheel or a cassette. Basically, cassettes come apart and you can slide off and rearrange the cogs or replace them with spacers, while freewheels have a group of cogs all connected together that screw onto the hub. A lot of older bikes with their original wheels have freewheels, as mine did, meaning that a single speed conversion kit won't work. Some people recommend just screwing on a single speed freewheel[3], like the sort you would put onto a BMX, but this would mess up the chain line as the wheel on a multispeed bike will be dished to allow space on the driveside to fit a multispeed freewheel, and a single speed freewheel is much smaller. You can redish the wheel, but this was beyond my expertise, so I just kept the 5 speed freewheel that was already on the wheel. Maybe later I'll learn about re-dishing the wheel, as single speed freewheels aren't that expensive. Having all the cogs also made it super easy to pick the cog which had the best chainline to the front cog.
1: https://www.planetx.co.uk/i/q/SKOOSSKK/on-one-singlespeed-converter-kit
2: http://www.sheldonbrown.com/free-k7.html
3: https://www.sjscycles.co.uk/freewheels/16-ird-defiant-332-inch-single-freewheel/
To keep tension on the chain and to ensure that the chain stays on the correct rear cog, I bought a chain tensioner. This is a bit like a stripped down rear derailleur. THe type I bought is spring loaded and screws into the rear mech hanger. Specifically I bought the 4 Jeri SS Chain Tensioner[4]. I could have removed the rear mech hanger completely and used the horizontal dropouts on the frame to set the frame tension, but I find using a chain tensioner much easier and reduces maintenance.
4: https://www.bikeparts.com/BPC148137/4-jeri-ss-chain-tensioner-black
I replaced the seatpost with longer one, making sure to check the diameter of the bottom of the seatpost to fit into the frame AND the top of the seatpost to make sure it fits into the seat clamp. Maybe in retrospect it would just have been easier to buy a seatpost that came with a clamp, but I was trying to save on materials as much as possible.
The last thing I did was replace the bar tape, as it had become all worn down. I watched a tutorial from Park Tool[5] on how to properly wrap the tape:
5: https://www.youtube.com/watch?v=5MzIiv7pewE
I finally got this bike out of storage after the summer break. I counted the gear ratio, it's got 46 on the front and 16 on the rear, which is nearly a 3:1 ratio, which is actually quite normal for single speed bikes, though possibly more suited to a fixed gear than a freewheel like mine.
