Bicycle Mechanics - Single-speed / fixed chainline question
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I'm thinking of building up a fixie / single-speed bike as my next project. Just how "exact" does the chainline have to be on fixies / single-speeds? i.e., +/1 mm, +/- 2mm? What problems arise if the chainline is less then perfect? Does the chain have a tendency to derail, or is the issue more to do with accelerated chain wear?
06-26-06, 11:07 AM
i would say no more than 2 mm. if your chainline is off, your chain can/will derail, causing you to fall and break all your bones. chain wear will be accellerated in a weird pattern on your chain as well.
06-27-06, 08:33 AM
Hi, I've been riding fixed gears on road and track for over thirty years. When you set up the chainline, it has to be <dead on>. This is absolutely critical. If it is not, as you ride on the road, the chain will "stretch." Then one day, as you are spinning at high speed down a hill at about 140 rpm's, the chain will fall off the chainring. If you don't have a lock ring, the chain will jam around the bb and the rear tire, the cog will unthread, and you will coast/brake to a stop. If you use a lockring, the rear wheel will lock, the bike will fishtail, and you may crash. So on a road fixie, keep the brakes and toss the lockring.
On a track bike, you want the chainring dead on because then you can run a looser chain. Much faster. When the chain is set up properly, it's difficult to make it derail. This is also why you want to use a 1/8" track chain. They are made to run straight, not to easily derail in order to facilitate smooth shifting.
06-28-06, 10:51 AM
I am interested in this question too, but in regards to single speeds with a rear derailluer used to take up chain slack.
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