Another question...

7 replies to this topic
  • crfmatt

Posted June 29, 2005 - 02:58 PM


Sorry guys but i have another dumb question... I am changing my rear sprocket because it is worn down and I just read something about how you should replace the chain at the same time??? :)

  • John_Lorenz

Posted June 29, 2005 - 03:09 PM


Whats the question?

Are you asking if you should get a new chain?


  • grayracer513

Posted June 29, 2005 - 03:40 PM


That depends. You will have to determine what state the chain is in to decide this. With an aluminum rear sprocket, and one of the higher quality O-ring chains, it's possible to wear the sprocket out and have the chain still well within specs. In fact, on my CR500, I replaced two rear sprockets while running the same Regina chain, and the chain was still near perfect.

If you are using a middle to low quality chain, you should just dump it. If not, there are several ways to check the chain you have. First, check to be sure it has no tight links, links that don't pivot freely. Next, wrap it over the new rear sprocket. If you can pull the chain back away from the sprocket at the rearmost point far enough to slide a 1/16" drill between the chain and sprocket, you should pull the chain off and measure it. The procedure is in the manual.

When measuring, note that the wear limit given (6" for the ten pin section) is equal to a 2.5% increase in length. One percent is about all you should tolerate if you're using the chain on a new sprocket, since more than that will wear the new gear more quickly than it should. Use 5.91" instead, and be sure to measure several sections to be sure there isn't one bad spot in the chain.

Otherwise, you can lay the chain out on a bench next to a new one and check the difference in length, or see how much lateral bend you can put on it compared to a new one. The second of these is a judgment call, and is somewhat imprecise by nature.

The wear pattern will tell you a good deal about the chain, too. Teeth that have the look of "leaning", or having been pulled forward on rear sprockets (backwards on the front) indicate the chain is too long, and no longer matches the pitch of the sprockets. Rear sprocket teeth that are worn thin, but still look pretty much straight up vertical, even hooked back slightly (again, fronts are opposite, so they'll be hooked forward), are signs that the chain may still be usable.

  • MisterMan

Posted June 29, 2005 - 08:36 PM


yes :)

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  • crfmatt

Posted June 29, 2005 - 08:42 PM


Ok, Thanks alot! I will find out what kind of chain it is when I take it off and I will check it with what you told me to decide to keep it or not.

  • Chris_from_Oz

Posted June 29, 2005 - 10:21 PM


It's cheap insurance to replace the sprocket bolts now too.....

  • crfmatt

Posted June 30, 2005 - 01:17 AM


It's cheap insurance to replace the sprocket bolts now too.....

Thats what started the problem...I just bought the bike and after a few rides i was hearing a weird sound and i stopped only to find 3 of the bolts missing :) . But after i hauled it home i couldnt find the right bolts anywhere so I just went ahead and got a sunstar aluminum on ebay new for $20 w/ shipping :) So that way the stock bolts will work because the sunstar is designed for countersunk bolts unlike my current sprocket.

  • grayracer513

Posted June 30, 2005 - 07:12 AM


Ironman, for one, offers reasonably priced, very high quality rear sprocket bolts for $9 a set.

Check Here

Scroll down about a third.

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