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Oval chain ring help.

Old 11-25-09, 02:32 AM
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Oval chain ring help.

So through riding my fixed gear and riding hard daily, my chain ring has come to be an oval shape, I can tell because my chain is tight when my crank is in some spots and loose when in others. It just so inconveniently happens that where I do my skip stops and such is where the chain is loose. Is it possible to just unbolt my chain ring from the crank, rotate it as close to 90 degrees as I can, then reattach it to my crank? What I'm hoping to attain here is making my chain tight in a different spot, so it doesn't come off when I'm trying to skid or do a skip stop. I don't have the money to buy a new chain ring right now, so this will only be a temporary fix. Thanks in advance!
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Old 11-25-09, 03:04 AM
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I really don't think your chain ring has become oval, it's much more probable that it's an alignment issue.
www.SheldonBrown.com to your help:
"
Chain Tension

he chain tension on a fixed gear is quite critical, and is regulated by moving the rear axle back and forth in the fork ends. If the chain is too tight, the drive train will bind, perhaps only at one angle of the pedals (chainwheels are not usually perfectly concentric). It should be tight as it can be without binding. If the chain is too loose, it can fall off, which is quite dangerous on a fixed gear.

Set the rear axle so that the chain pulls taut at the tightest part of the cranks' rotation. One at a time, loosen up each of the stack bolts, and tighten it back just finger tight. Spin the crank slowly and watch for the chain to get to its tightest point. Strike the taut chain lightly with a convenient tool to make the chain ring move a bit on its spider. Then rotate the crank some more, finding the new tightest spot, and repeat as necessary.
This takes a little bit of your hands learning how hard to hit the chain, and how loose to set the stack bolts, but it is really quite easy to learn.
Tighten up the stack bolts a bit and re-check. Tighten the stack bolts in a regular pattern, like the lug nuts on a car wheel. My standard pattern is to start by tightening the bolt opposite the crank, then move clockwise 2 bolts (144 degrees), tighten that one, clockwise 2 more, and so on. Never tighten two neighboring bolts in a row. You may prefer to go counterclockwise, but try to get in the habit of always starting at the same place and always going the same way. This reduces the chances of accidentally missing a bolt. Once you have the chainrings centered and secured, adjust the position of the rear axle to make the chain as nearly tight as possible without binding. Notice how freely the drive train turns when the chain is too loose. That is how freely it should turn when you are done, but with as little chain droop as possible."
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Old 11-25-09, 03:14 AM
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Thanks, I'll give that a try tomorrow, and if it doesn't work out for me I'll come back.
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Old 11-25-09, 07:19 AM
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It's quite possible that your chainring is just severely worn in the areas where you tend to apply the most pressure (on the downstroke and/or reverse downstroke in this case). Try the alignment first though. It's certainly cheaper.
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Old 11-25-09, 07:31 AM
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You might also want to try flipping the chainring "inside out" if it is worn.
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Old 11-25-09, 12:41 PM
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Is this an old crankset and BB? I had all kinds of problems setting chain tension on a 30-year-old crankset with a bent spindle. Spin the crank, or watch it when you're pedaling on an empty road, and see if the front of the chainring wobbles at all. I replaced the crankset and BB and never threw the chain again.
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Old 11-26-09, 01:10 PM
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Originally Posted by CaptainCool
Is this an old crankset and BB? I had all kinds of problems setting chain tension on a 30-year-old crankset with a bent spindle. Spin the crank, or watch it when you're pedaling on an empty road, and see if the front of the chainring wobbles at all. I replaced the crankset and BB and never threw the chain again.
No, it's a new Sugino crankset, and the bottom bracket can't be more than 500 miles old. I tried realigning it, but it just went back to the way that it was after about 30 minutes of riding, and I made sure all of the stack bolts were tight. So I'm starting to think I'm due for a new chain ring. Has anyone had any experience with the Sugino Messenger?
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