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Wed, 13 Sep 2006

Wheels that are round and brakes that work on the single speed - 22:45
So I had some mountain bike rims sitting around the shed when I built my single speed, I knew there were some problems with them, however I was feeling too cheap at the time to spend money on new rims for a single speed I was trying to build cheaply.

When you hit gutters or other blunt objects with enough force to flatten a tyre (pinch flat) it will sometimes happen that a flat spot forms on the rim. Sometimes these can be hammered out, sometimes not. The problem can be made worse by weak sidewalls in rims, which are caused by wear from rim brakes (v-brakes and similar). Both the rims in the shed had large flat spots and weak sidewalls (splits appearing in places, and pronounced flat spots (one on each rim)).

The flat spots meant I had to have the brakes backed off a lot so they would not hit the rim as the flat spot passed the pads, thus the brakes were set up sort of loose, however once per revolution of the wheel they would be very tight and responsive for a short time. This was not a problem until such a time as you wish to utilise the brakes, at this time the flat really good braking set up on one point on the rim would cause a thunk sort of instant deacceleration which on the whole was rather disconcerting.

Fortunately for me a friend moving to the UK for a while and needing to dispose of some bike bits was happy to exchange a spare pair of wheels for a case of coopers. The hub on the rear wheel was fairly stuffed (pitted cones, bearing surfaces and worn bearings) so could probably use replacement, and the front wheel has radial spoke lacing, however when it fails I can put a sensible spoke pattern in. This pair of wheels have the distinct advantage of not being too worn out on the braking surface and having no flat spots.

I put the front wheel onto the single speed yesterday and hey what do you know, the brakes worked once adjusted, it was almost a revelation. Tonight I rebuilt the back wheel with a hub I had sitting in the shed that is in much better condition and a similar revelationary experience happened with respect to braking on the back when I put the wheel onto the bike.

Three cheers for an improved single speed experience, it will be rather enjoyable being able to stop somewhat predictably.

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