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Sunday, April 28, 2013

Slightly Oval Chainring - Look for better quality!

Q

Hi Charles,

I own a good quality fixed gear bike. Nonetheless, is it normal for there to be tight and loose spots on the chain. When the crank side arm is facing front, the chain is at it's tightest. Turn 180 and it is loose. It is not so loose that it will come off the chain ring. For a Campagnolo crank I was expecting higher tolerances. I have read that tight and loose spots are to be expected on a fixed gear bike. I would like a second opinion. What is yours in this matter. Thank you

Andre


A

Hello Andre!

It is the result of lower quality chainrings and cranksets that are more oval shaped instead of perfect circles. It is only off by a mm or so, but its enough to be annoying. (With bicycles, being off by even 0.5 of a mm is often a big deal.)

If it bothers you then you can purchase higher quality parts that are more perfectly round.


Make sure you mounted the ring properly. Try removing the chain ring and remounting it slowly by tightening the bolts, every 2nd one in a star pattern, so they are evenly tightened. Tightening all the way on one side and going around can warp the aluminum ring. Let me know if this works and helps you. :)


The companies that are making such shoddy parts are the ones who like to spread the claim that such imperfections are "normal". Yes, imperfections do happen. Its the result of a faulty manufacturing process that results in a percentage of chainrings being slightly oval shaped.

Even better quality companies sometimes have this problem, but their quality control should be ensuring that the chainring is as close to perfectly circle as they can make it. And anything less than quality should be tossed and recycled.

But claiming that such imperfections should just be "accepted" as normal is misinformation on their part.

Sincerely,
Charles Moffat
The Bicycle Mechanic

PS. I do agree, I would expect better quality from a Campagnolo chainring. If I was the manufacturer I would be apologizing and offering to send you a new one.

FOLLOW UP

Hi Charles,
 
I just finished putting my bike back together. I followed your directions and found there to be much less play on the loose side. Much better!
 
Thanks
 
André

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