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Singlespeed & Fixed Gear "I still feel that variable gears are only for people over forty-five. Isn't it better to triumph by the strength of your muscles than by the artifice of a derailer? We are getting soft...As for me, give me a fixed gear!"-- Henri Desgrange (31 January 1865 - 16 August 1940)

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Old 01-27-09, 04:52 AM   #1
tommyd49
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Centering Chainrings - Is it Worth it?

Not sure if this would be better place on the mechanics board, but I'd imagine a lot of people on here have experience with this.

I've nearly finished my first fixed conversion. I'm using a brand new 14t Surly Cog, 39t Campagnolo Xenon crankset (originally 52/39t) and KMC Z chain. The problem I'm having now is that having looked at Sheldon Brown's article on fixed conversions, he explains how to centre the chainring.

Now I've greased the washers between dropouts and axle nuts and really loosened the chainring bolts (I can wiggle the ring back and forth about 3/16") but no matter how hard I push the rear wheel up, when I tighten the right axle nut, the chain just won't bind at all. I've been able to get it so there's less than 1/4" of droop, but nothing more than that.

My question to you experts is, shall I just leave it like this? It is a new crankset of reasonable quality, maybe it just doesn't need centering?
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Old 01-27-09, 07:02 AM   #2
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I'm a little confused by what you're describing. Are you saying you're unable to get the chain tension high enough to make the drivetrain bind? That should be pretty easy to do using the method mentioned at Sheldon's site, alternately tightening each axle nut and rocking the wheel back into position. Regardless, you don't want the tension that high (i.e. super-tight, no slack) since you obviously don't want it binding when you ride.

When your chainring is off center or imperfectly shaped, it may tend to bind during part of the crank revolution. If you're not seeing a difference in tension as you turn the crank, then don't worry about it.
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Old 01-27-09, 10:35 AM   #3
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And you shouldn't run your tension that tight anyways.
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Old 01-27-09, 12:02 PM   #4
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He's not referring to riding with the chain that tight, he's talking about this method for centering the chainring.

If you aren't having problems with your chain tension, then it is not necessary to center the chainring. Since you can't get it to bind, your chainring is probably fine.
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Old 01-27-09, 12:58 PM   #5
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I'm saying that you shouldn't ever be riding with a chain that's so tight that you have to worry about it.

Hell, I've run biopace fixed before.
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Old 01-27-09, 01:13 PM   #6
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having encountered an eccentric chainring problem once or twice, ranging anywhere from a slipped ring to a bent isis spindle, it's pretty simple to see the tight and loose spots if your overall tension is proper. particularly on converted road cranks, the ring will slip back relative to the position of your preferred skidding foot.

tension the chain until there's about 2cm of vertical play, then rotate the cranks in 30-45 degree increments, checking the play at each location. if you don't see a noticeable deviation in the play, then your tension is even.
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