TITLE: Rebuilding a bike
DATE: 2018-07-25
AUTHOR: John L. Godlee
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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:

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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.

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Lots of people suggest using a [single speed conversion kit] to
change the gear setup, but these rely on the rear wheel having a
cassette on the backwheel, rather than a freehub. [Sheldon Brown]
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],
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.

  [single speed conversion kit]: https://www.planetx.co.uk/i/q/SKOOSSKK/on-one-singlespeed-converter-kit
  [Sheldon Brown]: http://www.sheldonbrown.com/free-k7.html
  [single speed freewheel]: 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]. 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 Jeri SS Chain Tensioner]: https://www.bikeparts.com/BPC148137/4-jeri-ss-chain-tensioner-black

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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] on how to
properly wrap the tape:

  [tutorial from Park Tool]: https://www.youtube.com/watch?v=5MzIiv7pewE

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Update - 2018_09_09

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.